What determines whether two signals of equal amplitude combine to produce a 6dB gain or a 3dB gain in signal level (voltage or SPL, but not power), is the “correlation” of the signals at the point of combining. FULL CORRELATION CASE: If the correlation is 100% between the two source signals at the location where the combined signal is being measured (the two source signals are received with identical amplitude and with identical phase) then a 6dB gain in level (SPL or voltage, but not power) is achieved. Example 1: Two side by side subwoofers which are both fed the same signal (with the same amplitude and same phase) and which are both equal distant from the measuring device. In this case, the measurement device will measure a “combined” signal which is 6dB higher in SPL than that measure by either subwoofer alone. For a sine wave signal source, the two source signals would always have their sine wave peaks “synchronized” and always providing a doubling of peak level. And we know that a doubling of level (voltage or SPL) results in a level gain of 6dB. However, it is important to note that the “power” delivered to the room is only 3 dB higher than that delivered by either subwoofer alone (a doubling of power results in a gain of 3 dB). NO CORRELATION CASE: If there is no correlation between two non-identical, but equal amplitude, signals at the location where the combined signal is being measure, then a 3dB gain in level (SPL or voltage) is achieved. Example 2: Two side by side subwoofers are fed pink noise signals generated from two different noise generators (the pink noise signals are not correlated). In this case, the measurement device will measure a “combined” signal which is 3dB higher in SPL than that measure by either subwoofer alone. The two signal’s peaks and valleys will only be in alignment part of the time. And over time, the signal alignment of the peaks will vary between in phase (0 degrees) and out of phase (180 degrees). And the average increase in SPL or Voltage signal level achieved will be 3db higher than that delivered by either subwoofer alone. MAINTAINING 100% CORRELATION ISNT ALWAYS EASY Even in example 1 above, if the SPL meter where to move around the room, the path length from each subwoofer to the measurement device would change differently for each subwoofer, and the correlation between the two signals being combined would not stay at 100%. The axis of the room where the measurement device is equidistant from the two subwoofer will always receive the 6db gain in SPL. But there will be some locations in the room where the path length from each subwoofer would result in a 180 degree phase shift at the measurement device, and the signal would be cancelled. But most people, who are not equidistant from both subwoofers would experience a 3 dB gain in SPL. Another interesting example is the case where two signals of varying phase are combined. Example 3: Two side by side subwoofers are fed sine wave signals from two different signal generators (one at 60 Hz and one at 61 Hz). In this case, the measurement device will measure a “combined” signal which varies in SPL reading over each one second period. For one instant in each one second period, the measurement device will measure a “combined” signal which is 6dB higher in SPL than that measure by either subwoofer alone. But AVERAGED over the full second period, the measurement device will measure a “combined” signal which is 3dB higher in SPL than that measure by either subwoofer alone. In summary, achieving a 6DB gain in SPL with two subwoofers only occurs where the resulting phase difference between the two identical subwoofer signals at the measurement position is near zero degrees.
Nice explanation of parallel vs series wiring with visual examples! I think anyone studying electronics or amateur radio should check out this video. Nicely done!
So far, the best video I've watched in the 36hrs I've been trying to understand about speakers. I have these 5.1 speakers I found in our basement with it's player already disposed of that I want to use as a pc speaker, and I'm trying to learn how I can install them when there's just one front and one rear 3.5mm headphone/speaker jack, though it's got a sound card that supports up to 7.1, for the life of me, I have never been interested in electrical wirings until now. I don't how I can wire them all into one jack, or do I need to install another sound card with more ports, or buy some whatnot to connect them to. If they get more expensive than buying a pc speaker, they're going back to where they came from, useless. I'm going to follow you from now on and learn.
36 hrs.? get some sleep, trust me, it's not that exciting and rather simple to learn - make it last cause after slew rate and damping factor there is not much on the horizon.
🎯 Key points for quick navigation: 00:00 *🔌 Introduction to Speaker Wiring* - The video introduces the concepts of speaker wiring configurations: parallel and series. - Explains the upcoming experiments with volume and impedance. - Sets the stage for learning through real-time demonstrations. 00:28 *🎚️ Demonstrating Parallel Connection* - The first experiment shows how connecting a subwoofer in parallel affects volume and current. - Demonstrates a 6dB increase in microphone reading with parallel wiring. - Current from the amplifier doubles while voltage remains constant. 02:19 *📊 Understanding Ohms and Current* - Discusses the relationship between speaker impedance, current, and voltage. - Describes how impedance affects amplifier load and current output. - Introduces Ohm's Law and its relevance to audio systems. 04:04 *🔄 Effects of Series Connection* - Demonstrates the impact of connecting speakers in series on volume and current. - Shows that series connection results in a 0dB change in microphone reading. - Discusses the division of voltage and current between the speakers. 06:04 *⚖️ Limitations of Series and Parallel Wiring* - Compares the advantages and limitations of series versus parallel configurations. - Emphasizes the resistance changes with frequency and its effect on performance. - Notes practical limits of speaker configurations in parallel and series setups. 08:00 *🎶 Impedance Measurement and Efficiency* - Explores the impedance characteristics of speakers across different frequencies. - Highlights the importance of driver and enclosure compatibility for optimal performance. - Concludes with a summary of the video’s main points and encourages further exploration. Made with HARPA AI
I agree, two speakers outputting 20 Watts each is 40 Watts total, but speakers in unison do not add sound pressure levels linearly, they just push more air in parallel but at the same loudness. So dB in sound pressure does not always double when two speakers are driving the same signal at the same power level compared to one speaker doing the same. Take your stereo for example. You hear a tone pan from the left to center to right. When in the center, the sound is not louder, it is just balanced and sounds like it is from the middle. Each ear is hearing about the same volume level (just slight delays due to distance and echos in the room) but the sound from both speakers don't add up (in a perfect acoustical dead room) they just sound fuller. With head phones, you can get a wider separation but less fuller because each ear hears only one speaker for the most part. This is why there is a sweet spot in your stereo room where the sounds balance out to about what you get from headphones. Stereo recordings are designed for the left channel for the left ear and the right channel for the right ear. So in your stereo room - which should be acoustically dead, the sweet spot has no echos from the room and the program (music) can be listened to as it was intended.
At the 4:59 mark, with ONE speaker, you've got: V=20V I=1A R=16ohm This doesn't follow ohms law. Since the speaker resistance is set at 16ohms (perhaps slight variation considering it is a non ohmic device), it would not draw 1A of current, it would only draw the current required to keep ohms law intact. Please correct me if I'm wrong... From that time stamp onwards, there are similar errors carried through
Nice! This, along with many of your other lessons and demonstrations, should be mandatory study requirements for all "Audio People", especially live performance types!!! Most of them are clueless and believe myths of their predecessors, urban legends, hearsay and of course: "that's the way it is, everybody knows that!"
So when do I make a follow up video explaining that the terms “doubling” and “halving” aren’t totally accurate. They’re better than 99% accurate but to be precise, the increase is 1.995x not exactly 2x. Does anybody care?
It should also be noted there are some practical considerations that need to be taken into account when doing things like this. When you let an amp drive a one or two ohm load, you're beating the crap out of it. Playing music through a system isn't the same as taking measurements on a test bench. Also, you have to consider distortion. The harder an amp works, the more it distorts. Its unavoidable, and the amount of distortion an amp produces is directly related to how well its made. 2 power amps may be rated for the same amount of output in watts/ohms, but one may have half the distortion, and in the real world, that would make it a much more powerful amplifier. I see in a lot of the comments, people seem to think they will be "loosing power" if they don't lower a speakers resistance so the amp puts out its rated full power at one or two ohms. Lowering resistance forces the amp into a situation where it has to work harder to deliver the same amount of performance than a speaker that is less demanding to drive, like one that drops no further than 5 or 6 ohms. The practical solution in a situation like this is to turn the volume up. That's why its better to present the amp with a speaker that's easy to drive in the first place. It leaves you with the freedom turn the volume up without fear that you will damage your amp or speakers. Just to be clear, from what I could tell, everything covered in the video appears to be accurate. Nothing is wrong with the content. My concern is things were left out. Most likely there will be a future video covering the issues I raised above. So my advice would be to wait for future videos covering the rest of the topic before making any purchase decisions.
When you raise the amplifier by 6dB it makes output voltage doubled (20V to 40 V) , and current flow also doubled as manner (1A to 2A).calculating the (P) power it show 4 times increment as this: 20V x 1A =20W and 40V x2A= 80W. Clearly 80W means 4times like 20W. But when you attached additional speaker it only cost more current, but no voltage increases, resulting power = 20V x 2A = 40W. My question is, why the measurement mic showing 6dB same increment at both testings above, while the amplifier produce completely different power output as, 40w vs 80W.
I'm not into SPL. Just good tone with best coverage for speaker, whether one or two or amount of ears listening. If a venue has capacity of 10,000 sets of ears and 10000 minds or 10000 bodies, how much power is needed in subpower for 1/2 of 10000 bodies in avenue that is designed for 10000 bodies. That seems more reasonable for life of any subwoofer. Using math to figure out impedance load is cool but in real world, a knowledgeable sound engineer needs to understand this in order to do a solid sounding show.
@@rgortega1285Most (sound engineers? are selectively deaf (notch filter damage in their hearing range). I walk out of so many concerts that i've quite going. When is their mommy going to tell them the truth?
I still don't get it. Doubling the power on one subwoofer results in a 3dB gain. But the same power split on two speakers suddenly should gain an additional 3dB so 6dB total? How can 3dB magically appear out of nowhere? Where is this "acoustic energy" supposed to come from?
There is only 3dB more of total energy being produced. But in certain sweet spots, such as right in front of the subs, the phases will be aligned, the wavefronts will add together, and you'll hear a 6dB increase. In other locations, such as off to the side, the wavefronts will be out of phase, destructively interfere, and you'll hear much less than a 3dB increase (maybe even negative, depending on the frequency and the distance between the subs).
@@kornielsen9471 Partially true, the standing waves effect you described is already counted for in the +3db. Standing waves can be negated by placing multiple subwoofers asymmetrically in the room (Dr. Earl Geddes's thesis).
@@dingdong2103 I am not referring to standing waves, which complicate things even more. Outdoors (with no standing waves), if you are exactly equal distance from both subs, you will hear a 6dB increase when you turn on the second sub. In other locations, it will depend on the frequency and distance delta, but the average will be a 3dB increase.
@@kornielsen9471 What you refer to is exactly what standing waves do in a room, summing and canceling of signal... Outdoors there will be just 2 clean signals. And the summing of signals only happens if the two drivers are within a wavelength of eachothers.
So if i were to use 4x 8ohm 15" Woofers in Parallel, what would the Ohmage then be? And by adding any other speakers (8ohm) (but not woofers), does this have any (negative) impact
That would effectively be 32ohms. If you have an amp that can handle that, go for it. You can add more speakers if you wish, but keep in mind the impedance will also go up, and you might end up working your amps so hard that they die. A good practice would be to match your amp impedance if possible, that would be either by connecting your speakers in a series/parallel connection or getting more amps for your speakers if you have the budget
Thanks for sharing BUT NOW what if you got 4 12inch speakers in one guitar cabinet and the are factory wired in Series/ Parallel...how does that read on amp output? Thanks again.
What it is two separated active sub ? +3db ? I dont understand when you say +3dB acoustic power. Because the power produced by the added membrane, is the exact additional power transmitted by the amp. So why do you count it twice ? (+6dB)
With two separate active subs, you would expect a 6dB increase from the second sub being added, because behind that second sub is also 3dB more power from an additional amp.
If you double your cone area you double the efficiency that each cones can turn the motion of the cone into sound waves in air. It is a very lossy process. In other words both cones now produce twice as much sound as they normally would on their own. Like paddling a canoe with a broom stick vs a paddle - you exert the same amount of energy with both but you go twice as fast with the wider paddle because it can transmit your energy into the fluid water with greater efficiency.
The issue is not just the nominal impedance of each speaker, it is also the absolute minimum impedance at a certain frequency. As we saw in this video, the graph of impedance by frequency for a given speaker has peaks and troughs. So with music containing a particular frequency at a high level, a frequency which corresponds to a very low trough on the impedance graph, the current in the amplifier could increase beyond what its circuits can handle, thermally speaking.
There is no such thing as "3 dB more from the speaker". The amount of available power is what voltage*current shows - period. What you are demonstrating with "3 dB more from the speaker", is actually a coherent speaker array. Try moving your meas mic up and down and you see that the +6 dB isn't consistent. Also if you switch the polarity of the second speaker, when in parallel configuration, you see that the measurement from the front drops dramatically, as the phase fronts from two speakers are cancelling each other.
Speaker output is rated as: SPL, Sound Pressure Level. Power, in Watts, is: P=EI, power equals Voltage times Current. And and real work, in a motor, or speaker coil winding, is performed by: Current. You can have a lot of voltage, but if there isn't a closed circuit, with current going through a circuit, there is no, "work," being performed. Such as a wall outlet, with nothing hooked up. Speaker output is usually expressed in dB, decibels, & measured by placing the speaker in an anechoic chamber, with an input of a tone of: 2.83 volts, & a mic pointed at them, one meter away. With an input impedance of 8 ohms, this is about one amp. My Klipsch speakers are about 98 dB efficient; they produce 98 dB of sound output, a listenable level. Other quality speakers produce: 88 dB, about 10 dB less. 3 Db = twice the power; 10 dB = ten times the power. If voltage is constant, ten times the current, power.
Great video as always! I like that you don't just do the calculations, you measure things. In physics measurements are king. If your theory disagrees with measurements the theory is wrong. But I have an issue with this. What if you put 10 speakers in series? Your amplifier would output tenth of the power but you'd still get the same audio power. How? Let's complicate things even more. Now you connect 10 sets of these to the same amplifier in parallel. Your amplifier outputs the same amount of power as it did when driving just one subwoofer. Same voltage and the same current. Same power. But the audio power just went up by 20 dB. Let's have another thought experiment. You have 100 speakers. You connect all of them in series. Your amplifier outputs 1% of the power it was outputting with just one speaker but the audio power remans the same. You just increased the efficiency of the whole system by 100 times.. What if you had a 1000 speakers? Would your efficiency be 1000 times better? At what point your system's efficiency would be more than 100%? At what point would the system be outputting more energy than it's getting?
So can you add 2 outputs of the same channel on same amplifier to double the output power? My amplifier has 2 cg Channels and each channel has 2 outputs. I wandered to combine the output on each channel so I ended up with 2 outputs instead of 4.
With subs, you will max out acoustic efficiency somewhere around 30% depending on design. Meaning that your +6 db for every doubling of speakers starts to drop off and level off to +3 db. That should happen somewhere around 12 double 18" cabinets where you have reached maximum acoustic efficiency of the design and there is no more efficiency increase to gain by increasing cone area. Same with running speakers in series, you would reach a maximum volume and then start dropping off as the new speakers coming on line wouldn't be adding to the acoustic efficiency as maximum has already been reached and would also be physically far from the measurement location as you can't stack boxes in the same space of each other (damn Pauli exclusion principle).
At the 3:45 mark, I take exception to the idea that the second speaker adds 3db to the sould level. In a parellel arrangement, adding a second speaker doesn't change the voltage, current, or power going to the first speaker. Adding a second speaker doubles the amount of audio power produced (+3db). The load on the amplifier has doubled requiring twice as much current. Not only does this follow ohm's law, but also obeys the conservation of energy. To get a 6db gain, you'd have to also double the power consumed and produced by each speaker. But that didn't happen! The voltage and current are the same and therefore so is the power per speaker. The overall gain is only 3db. So, why did the test microphone measure a 6db gain?
Right, good question. What if you just doubled the current going to the first speaker alone? Then what would the microphone read? Of course this breaks ohms law, because you couldn’t double only the current and keep the voltage the same, but what you could do is increase the voltage and current each by 1.4 which would effectively double the power, which is the same thing. So in this case, we would get 3dB yes? And if so, if you split that power between two speakers instead of one, you’d have the 3dB from the doubling of power, but then also another 3dB from the doubling of speakers.
It's because its 6dB at a certain point in space. on average, you get +3dB. See for the formulas. If you double the acoustic intensity, you add 3dB. If you double the acoustic pressure, you get +6dB. He should have explained with formulas.
It's because most of that power isn't being transferred into sound, it's being wasted. You are not creating energy from nothing by adding boxes, it's already there, just not being utilized. Your speaker cone, being a solid, is high impedance and the air, being a compressible fluid, is low impedance. When you put a high impedance load into a low impedance load, well over 90% of your energy is wasted, sometimes as much as 99.9%. Most of the air just gets moved off to the side and eventually that motion ends up as heat and not sound. When you add another speaker, you double your cone area. That doubling of cone area doubles the efficiency of converting motion into sound of the whole system. That's where the second +3 db comes from, the increase in TOTAL system efficiency. Every time you double your speakers, you double your efficiency UNTIL you reach the maximum system efficiency possible and then that "free" +3 db's is no longer there. For direct radiator boxes (sealed, vented) that is about 25% maximum efficiency, horns can get you up to 50% total efficiency. So you get +6db's for every doubling of boxes until you reach that maximum efficiency, and then you only get +3db's after that for each doubling. Note that high frequencies will reach that maximum efficiency limit with fewer boxes then the lower frequencies. So when you double your box count you may get +6db's from say 20-55hz but only +3db's from 60-100hz because those higher frequencies may already be at their maximum. For horns you need about 8 boxes (subwoofers) to get to the maximum, for regular speakers you would need closer to 20 (double 18" ers) to get to their maximum efficiency, after that, no more +6, you only get +3.
Is it true that if you have 2 speakers and one speaker can handle more power than the other, the that speaker will take the extra power? So if you had a 10 watt speaker and a hundred watt speaker and a 100 watt amplifier you wouldnt blow the 10 watt speaker cause the 100 watt speaker would take the extra power.
I don't think so. If the speakers are of the same impedance, they will divide the power equally, and so I expect the 10 watt speaker will blow at high output levels. Normally, we handle speakers of different power ratings by only sending high frequencies to the lower rated speaker, via a crossover network, because most of the energy is in the lower frequencies of music. The half-way point for division of power in music is around 120Hz as I recall, just above subwoofer range. Two full-range speakers of different impedances could be a different matter.
I have a question, that answer I cannot find anywhere. I have a pair of 4 Ohm speakers and a pair of 8 ohm speakers. My integrated amp had a typical 8 jacks for connecting 4 speakers. The A is 4ohm-8ohm, and the B speaker slot is 8-16 and the A+B asks for all 8 ohms. Since I dont have 2 pairs of 8 ohm speakers, so can I somehow connect the 4 Ohm speakers at the same time with 8 ohm without damaging the 4 ohm speakers, as I understood that in case of connecting all 4 speakers they should be all 8 ohm?
Is the sound at the end taken by microphone? My subs got much quieter with increased impedance in the test during the last minute of this video, but the commentary then said that the volume was consistent during the sweep
As an RC car enthusiast, this is particularly confusing. We run batteries in series and parallel. Series combines the voltage (way more power!), parallel combines the mah (way more time to play, think of it as making your gas tank twice as big). Is it the same principle with speakers, because it seems to be the exact opposite? And to make things more confusing, both the amp and the speakers can change impedance depending on dual channel or stereo setup. So if we were to compare this to an RC car battery setup….is the speaker the battery, or is the amp the battery? On a side note, what happens to these setups you just showed, if the amp is in mono mode? Meaning can you run 2 speakers in series/parallel through a mono setup? And what would that do? You seem to have a strong grasp of this topic, any insight is appreciated. 👍
In the case of self-powered equipment, the couplings are not a problem, since each box has an amplifier for itself, and therefore there are no impedance additions or subtractions.
So what you were saying ( in a very roundabout sort of way ....) was by hooking up two 16ohm drivers in series makes no difference.... only half the output power gets delivered but I assume the decrease in radiation resistance makes up for this .... am I right ?
I like this video, I am new with speakers. I think there is an error at 5:31, the 8 ohm on left below the amp should be 16 ohm? Also, I would think you would want to measure things with one speaker at one volume level, then while measuring, turn up the volume to get 3db increase and see how much voltage and current are needed. Then you have a response curve to test against the equations. Maybe I missed that but seemed like you were keeping at same volume knob level setting the whole time.
So if you use 2 8ohm drivers in you dubbel 18'' sub woofer. and you wanna use 2 cabinets on one side on the amplifier. then you need to wire the speakers in serie?
What is going to hapen if we plug two pairs of 8ohm woofers but one pair is paraller and the other one in seriers to the first one? Will the resistance be the same as if we have just one woofer? And the output still be doubled? Or the output will cancel itself as well?
How do you have the meter leads on? I tried using a normal meter to test for voltage coming out of my car subwoofer amp, which obviously takes in 12-14v and i get weird numbers
It's quite interesting to see how using more speakers saves energy. Although I'd expect this to gradually taper off as you add more and more speakers, so maybe you'd only get 5 dB from 2 more subwoofers.
It doesn't "save" energy. The amount of energy being output from the amp more or less stays the same but the acoustic output changes. Adding an extra driver adds 3db of output and halving the resistance ads another 3db of output but the current also changes.
@@SilentShadow-ss5xp yes but if you want to listen at the same level it saves power. The example is illustrated best with the two series woofers that were the same level with half the current.
@@TimpBizkit Half the current EACH one, because they split the same amount of current that flows. In total is the same, so no savings, plus the cost of second driver equals spending more, not saving more :)
@@BOB-eb8xz but two series woofers have double the impedance. So half the current and the same voltage flows to the pair equals half the power to the two woofers that are as loud as one. The current doesn't split in two lines because it's a series setup - one "river" of current = same current to each woofer as total but voltage is split. Each woofer in a pair gets a quarter of the power (half the current and half the voltage). You will need more money for drivers and wood but less for an amp (and in big builds alternator and eventually fuel consumption, although the double box is heavier to move around). If you think about it, two speakers are a bigger "boat oar" on the air around them and thus convert power to sound better.
@@TimpBizkit wouldn't the best idea be keep the current the same just use woofer no.2 as a passive Radiator? Especially if the enclosures tuned correctly 🤔
I am looking to run 6 Bass. Is using 3 amps in mono, and connecting the othe 3 to the speakers better than running 2 per amp?. Try to make it powerful and cost effective. 6 Bass amps would be to expensive at this point. I appreciate your channel. Thank you.
Sorry but I have doubts : Series 16+16=32ohms : the amp produces same voltage and half the current, hence -3dB. Each speaker gets half the voltage (-3dB) and half the current (-3dB), therefore each speaker -6dB. Since there are 2 of them, the total acoustic output is -3dB (half the power). Parallel 16&16=8ohms : The amp produces same voltage but twice the current (+3dB). Each speaker gets same voltage (0dB) and same current as only one (0dB). Since there are 2 of them, the total acoustic output is +3dB (twice the power). Putting an infinite number of speakers in series will finally translate into 0 power, since the voltage at each speaker and the current will both tend to zero, or am I really really wrong ?
Voltage and current are both a part of one single equation. Voltage/Resistance=Current. If you lower voltage, current naturally follows. What you're doing is that you're basically saying that Four apples + Six oranges equals Ten fruits. Then remove Three oranges. Now you have Four apples + Three Oranges which equals Seven fruits. You don't say that you have Three fewer oranges AND Three fewer fruits all in all which is now a grand total of Six fewer fruits, do you?
@@Turntablist11 dunno about your fruit analogy, but as long as the amp behaves like a constant voltage source, my reasoning is right. Just try putting 10 speakers in series on a solid state amp and you will hear very little overall acoustic power.
@@paolozak3014 I just realized that I read your first comment wrong. What you are forgetting about though, is sensitivity. You gain 3db sensitivity when you double the amount of subs. This is true as long as you haven’t reached maximum sensitivity yet, which is around 100db (baffle gain, resonances, diffraction gain, and boundary gain not included). Two subs in parallel is 3db more sensitivity plus 3db current, so 6db in total. Two subs in series is 3db more sensitivity minus 3db current, so 0db in total.
@@Turntablist11 sorry but I can’t follow your sensitivity argument. Series : the amp delivers half the current & same voltage. Each sub gets half the voltage (-3dB, in series the voltage is divided) and half the current (-3dB), so each sub is at -6dB (1/4 of the power). Since there are 2 of them, in total we have -3dB (half the power). Parallel : the amp delivers twice the current & same voltage. Each sub gets half the current (1/2 of twice = 1) and same voltage, hence 0dB (no power loss). Since there are 2 subs, we have +3dB in total (twice the power).
@@paolozak3014 Loud, low, small. Pick two. That’s the basics of speaker design. A small loudspeaker that plays low frequencies will not be loud. Make it larger and it will be louder. When you double the amount of speakers, you gain more sensitivity, equal to about 3db.
@devinlsheets_alphasound - I'm super curious about running things in series. Theoretically, if I had multiple four 4-ohm subs with a 1000w rms rating and a 135dB half-space spl, and wanted to run two of them in series per channel so I could get away with fewer/cheaper amplifiers, how would I calculate the wattage rating to properly drive them? Can I double the recommended wattage like with a parallel configuration to see a +3dB increase in SPL over one cabinet for a pair in series? Is it a lost cause because of the inherent electrical and mechanical cancellations? If i do get amplification in a series deployment, would I see +6dB if I doubled that same configuration? Are there phase/output issues or other substantive issues that I'm failing to consider?
If you use powered subs to simplify the whole process, a lot more people will understand it. Basically doubling your speakers gives you +3db . If one sub max SPL is 135db, adding an extra sub would make it 138 db SPL Max, and to increase it another 3 DB you have to add two more subs, the four subs would produce 141db Max SPL and if you want to add another 3 db, you have to have eight subs to increase it to 144db SPL Max. Basically, you have to double the speakers for every 3 db increase you want in SPL.
@@devinlsheets_alphasound yes you're correct but I was just explaining the fact that if people want to get more SPL out of their system, they have to double their speakers for every 3db increase. If they use four passive subs instead of two, they will probably have to use two amplifiers to power them to get the additional 3db increase.
Unless your amplifier is already completely out of available power, adding a second subwoofer in parallel will automatically draw double the power from the amplifier, resulting in a total of 6 dB increase in your system when you add the second subwoofer. If you could theoretically keep the amplifier power the same all around through some artificial means, adding a second speaker would increase it by 3 dB.
Good effort and thanks a lot for the Video. I would like to experiment like you did, but hardly find opportunities with gears. To whatever I have learnt: Doubling the Voltage or current should result in 6 dB not 3 dB. Correct the video @3:24. Doubling Power results in 3dB change. Please correct me if I am wrong.
I've seen all the internet about this issue and this is the best explanation of all. I'm really impressed! But 3:44 you say that one more sub gives you +6db. Are you sure? I thought it would give you another 3db, not 6, so together they would make +6db and not +9db. Do I get it right?
@@devinlsheets_alphasound I appreciate you answer but my question remains unanswered. Sorry, my English is not perfect and I might have not made myself clear enough. The problem is mathematics. If one sub gives +3db, another sub should give another +3db, which would make +6 db all together. What I Understand from you video at 3:44 is that one sub adds +3db but another sub adds +6db which all together makes + 9db. Which is correct? Does the extra sub give +3db or +6db? Because the picture is confusing to me. Thank you
@@paul7000 one subs doesn’t give 3dB, it gives whatever dB you run it at, which depends on how big your amplifier is and how close you are to it. It might be 3, or 93, who knows. Adding the second speaker (and doubling the power) will add another 6dB to whatever dB the first speaker was putting out. If it was 3, then it’ll be 9 total. If it was 93, then it’ll be 99 total.
Don't forget with multiple drivers in a cabinet you can wire series/parallel meaning if all drivers are the same impedance then total impedance at socket is as one driver. All 8 ohms then total 8 ohms .my vintage Bose 802s are all in series with a 0.9 impedance per driver do you get anything from 7to 8 ohms
I suddenly Have a problem connecting front door speakers 2 a second channel makes really bad audio( IV had the sound system in the car for 4 years I was told it was either a bad rca cable or the input of the RCA was damaged, I used another amplifier and changed the RCA cable but I still have the bad audio I ended up connecting all four speakers to one channel parallel and now the audio is ok out of all 4 speakers in total the 4 speakers add up to 24 ohm speakers watts add up to just under 1900 watts and the amplifier is 3000 watts I'm wondering if this is safe until I can finally get the problem fixed by a professional the gain on the amplifier is not max it's around half maybe less not sure since it's just a cross that I twist left or right
Solid state amplifiers are rated at different speaker impedances. So my bass amp puts out 500 watts at 4 ohms, but only 350 watts at 8 ohms. I can use two 8 ohm speakers in parallel to achieve 4 ohms, or if there was 2 ohm speakers, two of those in series. It’s not the series or parallel connection that matters, it’s the total speaker load on the amp.
Look.... An ideal Amplifier with 350 Watts at 8 Ohm should give 700 Watts at 4 Ohms, Like the KRELL Amplifiers do. Because of internal resistance of your Amplifier, he is not able to double the Current, that is why he only do 500 Watts at 4 Ohm :-)
If they’re wired in parallel it will go up 3db. If they were in the same cabinet, and the cabinet was the proper size it would go up 6db. If those speakers are wired in series you’ll drop 3db. Ohms is a measurement of amperage, while volts is a measurement of Electromotive Force. But who cares?without getting crazy you can think of these two measurements this way. If you have a garden hose with water flowing through it, the volume if water coming out is its Amperage. The pressure of the water coming out is akin to voltage.
probably so you can run a shitload of them in parallel to a single amp Also, and that's speculation, higher impedance speakers use thinner and lighter wire on the coil, so, you may have a tighter magnetic gap and lighter voice coil, thus a better speaker overall
Greater speaker impedance means greater damping factor with a given amplifier. You may also use thinner cables for each speaker. Also you may have more speakers per channel as someone has already mentioned. You need a strong amp though. Nexo 4x4 is one monster amp.
very nice video, but I have some corrections and contributions 1) 6:20, while it is true DC resistance of voice coils, do vary with frequency, it is a very little change in comparison with reactance, which varies greatly. The text should say "impedance varies with frequency", which is not the same of resistance. But all of these varies with frequency, resistance, reactance and impedance overall. (ideally resistors have a flat frequency response, but complex AC circuits like speakers are very complicated and do exhibit non flat resistance component) 2) 3:34, I think what you tried to explain here is right, but not correctly explained. The dB scale for power is calculated as P (dB) = 10 * log10(P/Pref) While dB scale for pressure and voltage is calculated as V (dB) = 20 * log10(V/Vref) These formulae means that doubling the power is to add +3dB of power, but doubling the current, voltage or presure is adding +6dB of the quantity. That said, what really happens when you connect a second speaker in parallel with the first, while remaining a constant signal or voltage output, it is true the amplifier delivers +3dB of power, because it is doubling its power output, its impedance load is divided by two, thus power is multiplied by two, because of P = V²/Z . Where V remains the same and Z gets divided by two. Doubling the power is adding +3dB of power. Say for example if your first spkr is developing 1 Watt, the second spkr you connect will develop the same 1 Watt, while the power of the first one remains unaltered. Being the total power delivered by the amp just the double of just one speaker connected. But with SPL pressure is a different story. While signal/voltage V remains the same, the power of the first spkr will remain the same, and the second will develop the same power of the first. You have +6dB of SPL pressure output, because the pressure is multiplied by two , these pressures of every spkr is just added. and the dB scale for pressure is different that the scale used for power. Double the sound pressure (say in Pa units) will result in adding +6dB to the SPL. So why you have +3dB power in the amplifier and +6dB pressure at the spkrs?, why this 3dB difference? Because doubling the amount of speakers raise +3dB of the sensitivity of the system. Say for example one spkr has a sensitivity of 95 dB 1Watt/1meter, two speakers have 98dB 1Watt/1Meter. But this is far more complex because there are issues like vector sum, phase coherence, wavefront shape, polar response and many things that make this very complicated in practice.
Nice ok so: adding a second speaker in parallel but sharing 1W of power raises the total sensitivity by 3dB as measured by the microphone. So then, what if we also double the total power to 2W? The mic measurement goes up another 3dB, for a total of +6dB. If we double the power going to only one speaker, the mic reading only goes up 3dB. So what is the mic measuring?
@@devinlsheets_alphasound "adding a second speaker in parallel but sharing 1W of power raises the total sensitivity by 3dB as measured by the microphone. So then, what if we also double the total power to 2W? The mic measurement goes up another 3dB, for a total of +6dB." Yes, correct. " If we double the power going to only one speaker, the mic reading only goes up 3dB. So what is the mic measuring?" Assuming you disconnected the second spkr, and have only one, if you double the power (+3dB of power), you get +3dB of pressure. while doing this you multiply speaker voltage by 1.4142 (square root of two) the mic measures pressure, voltage reading of microphone terminals are proportional to pressure waves at the mic capsule, say for example a calibrated measurement mic could say its sensitivity is 1 Pa = 94dB SPL = 8.15 mV RMS. Pressure reference for the dB SPL scale is 20 uPa (twenty micro pascals) as in formula dB SPL = 20*log(P/Pref) Because power is proportional to the square of either voltage or current, the 10*log formula was chosen for power, and 20*log for voltage, current, and pressure that is proportional to spkr voltage. That way when you add +3 dB or +whatever dB to power, you get equal +dB to voltage or pressure. that means, adding +3dB of power (doubling power), you get +3dB at SPL pressure (pressure/voltage is multiplied by 1.4142 square root of two) Adding +6dB of power (multiplying power by four), you get +6dB at SPL pressure (pressure/voltage is mutiplied by two) Or in other words, if you multiply voltage by two, power will be multiplied by four, because power is proportional to square of voltage.
You have to consider the Amplifier's impedance output as well. Let me use 8 Ohm speakers because many amps have 2, 4, 8, or 16 Ohm outputs. All Voltage, Current and Watts are RMS in my discusssion. 4 Ohm Output: Two 8 Ohm speakers in parallel = 4 Ohms (impedance match), at 40 Watts: In this case the Amplifier will supply 40 Watts. 12.649 Volts out with each speaker drawing 1.582 Amps each = 20 Watts from each speaker for 40 Watts total. 4 Ohm Output: Two 8 Ohm speakers in series = 16 Ohms (impedance mismatch), at 40 Watts: In this case the Amplifier COULD supply 40 Watts but it can't. 12.649 Volts out but only 6.325 Volts get to each speaker drawing 0.791 Amps each = 5 Watts from each speaker for 10 Watts total. Since -3dB is roughly a 50% Power Loss, 40 Watts to 20 Watts is -3dB, and 20 Watts to 10 Watts is another -3dB for a total of -6dB (1/4 the Power). So even if the Amplifier COULD try to put out 40 Watts with two 8 Ohms speakers in series on a 4 Ohm output, it can't do that due to the impedance missmatch. This is why Amplifers usually have several impedance outputs. Since two 8 Ohms speakers in series is 16 Ohms, you should switch to the 16 Ohms Output (if the Amplifier has one): 16 Ohm Output: Two 8 Ohm speakers in series = 16 Ohms (impedance match), at 40 Watts: In this case the Amplifer will supply 40 Watts but now using a different voltage. 24.298 Volts out but only 12.649 Volts get to each speaker drawing 1.582 Amps each = 20 Watts from each speaker for 40 Watts total. So If you change the Speaker arrangement and not select the proper amp Output Impedance, you will get less power out of the Amplifier or you may overload the Amplifier and cause damage. So ALWAYS match the Amplifier's Output Impedance to the Overall Speaker Cabinet Impdeance. Examples: One 12 Inch Speaker at 100W at 8 Ohms = Cabinet 8 Ohms 100 Watts RMS (commonly used) Two 12 Inch Speakers at 100W at 8 Ohms in Series = Cabinet 16 Ohms 200 Watts RMS (less commonly used) Two 12 Inch Speakers at 100W at 8 Ohms in parallel = Cabinet 4 Ohms 200 Watts RMS (commonly used) Four 12 Inch Speakers at 100W at 8 Ohms in Series = Cabinet 32 Ohms 400 Watts RMS (Outputs for 32 Ohms are rare, not commonly used) Four 12 Inch Speakers at 100W at 8 Ohms in parallel = Cabinet 2 Ohms 400 Watts RMS (less commonly used) Four 12 Inch Speakers at 100W at 8 Ohms in Series/parallel = Cabinet 8 Ohms 400 Watts RMS (commonly used) Series/Parallel Arrangement of four 8 Ohm Speakers 100 Watts each arranged for 8 Ohms 400 Watts total: | ------- | | 8 Ohm 8 Ohm | | ------- | | 8 Ohm 8 Ohm | | ------- | So why are there 2, 4, 8, or 16 Ohm speakers? The lower the Impedance (ohms) of the speaker, a lower Voltage is required to drive it BUT LESS AMPS (current) is needed as well. Since current (Amps) is key is power distribution (think of High Voltage power lines), a 2 Ohm Speaker (or Cabinet) requires less current though the wires to get the power from the Amplifer to the Speakers. At home or small venues, 8 Ohms is fine, but in a large arena where the Speakers are up high and many feet away from the Amplifiers, 2 Ohm Speakers and Cabinets are better. Series/Parallel Arrangement of four 2 Ohm Speakers 100 Watts each arranged for 2 Ohms 400 Watts total: This Speaker Cabinet requres less current to drive the speakers and thus less current/resistance (IR) losses though the cables. Also, lower current cables can be of a thinner gauge which saves weight and cost. | ------- | | 2 Ohm 2 Ohm | | ------- | | 2 Ohm 2 Ohm | | ------- |
In the video 1 amp drives 1 speaker 1A 20v 16 ohm, so 20 watts. Does that mean when connecting 8 speakers in series with acoustic coupling the amp only draws 2.5 watts while having similar acoustical output as 1 speaker? 😮 Because 1 speaker: 20V 1A 16ohm = 20 watts. 2 speakers: 20V 0.5A 32 ohm= 10 watts, 4 speakers: 20V 0.25A 64ohm = 5 watts, 8 speakers: 20V 0.125A 128ohm = 2.5 watts. I know 128ohm could be high for an amp, but this is about understanding the theory. Using 4 ohm drivers would result in 32 ohm load in the same 8 speaker set up. Or to get deeper into it: 2 speakers in parallel would result increase +6db. Meaning having a big array of 32 speakers in parallel would increase the acoustical output by a massive +30db! I am thinking of building a compact line array system with a 3 inch driver delivering 104dB > so max SPL of a 32 speaker line-array system would deliver 134dB am I right?
Here's something I always wanted to know:- You build two subwoofer boxes with two 18 inch 8 ohm speakers each. You wire both speakers in both boxes in series. That would mean both boxes would be playing at 16 ohms. If you were to then 'daisy chain' both boxes together at the speakon connectors, would they then both be playing at 8 ohms or at 16 ohms?
If you wire each 8ohm speaker in a box in series, that would increase the impedance to 16ohms per box. If you then daisy chain(parallel connection) each boxes, that would lower the impedance to 8ohms.
The added benefit of doing what you say in say a club is that if you overdrive those boxes wired in series internally, you will only ever blow 1 of the two drivers as as soon as 1 blows, the series circuit opens up saving the other driver. If you wire the boxes internally in parallel, you will most likely blow both drivers if you overdrive them. This is a huge consideration when designing a club system for DJ's etc to use. The cost difference between replacing half vs all the sub drivers can be astounding.
so, parallel divided curent, series divided voltage. parallel increase SPL uses more power, series do not increase SPL but saves power 🤔 once again. great content, 👏👏👏👏 you guys should have 1M of views not like others that all they do is play their favorite songs but have 1Ms of views... people are so pathetic. 🤦♂️
I am about to go from 1 18" Resilient Sounds platinum to 2 18" in my truck. I will also be going from one Down4Sound JP23v2 to 2, or one per sub wired at 1 ohms for a total of 5600 watts I hope to get 6 dbs or slightly more, because of acoustic coupling because the 2 subs will be right next to each other, literally 1 inch apart.
I see there is diminishing returns for every subwoofer after the the second (amp/sub). The SPL calculator has +6.0, +3.5, +2.5, 2.0 db and so on. I'm almost finished building two vented boxes each with a 24" subwoofer tuned for 23 hz (internal volume 11 excluding ports, bracing, driver). This is for an outdoor audio/concert setup. Reinforces the fact on how important the sensitivity and frequency response of a subwoofer or driver is. It can get incredibly expensive or consume a ton of electricity.
Yes, because our sense of SPL is logarithmic, not linear, so it takes exponentially more power or number of subwoofers to increase things equally in proportion each time according to our sensitivity to SPL. If you have one sub, adding another will “sound” about the same amount of increase proportionally as having 50 and adding 50 more.
@@dingdong2103 how do you determine the box? Hornresp? The videos on RUclips look like pro audio clones but it's obvious the driver parameters are important after using WinISP.
@@stiffmeister0hYeah Yes hornresp is an excellent tool. I built a few tapped horns with 21" 18Sound drivers and the actual response was dead on as predicted. +-3db from 80 to 20hz room response in a mid size cinema. System pushes easily 130db clean and punchy bass.
@@dingdong2103 well I have a third 24" sub that is currently in a box with four 12" passive radiators (Earthquake PUMP-12x2). Unfortunately, I did not brace the box enough and it vibrates. I'm going to dig in and see if the braces came loose plus figure out resonant frequency of the radiators. However, having the driver out will allow me to play with hornresp. I just recently learned of horn resp while building these behemoth vented boxes. The 15 cf external dimensions are just enough if not too much. Recommended 16 cf internal and holy cow too much space.
Yes but wiring say a double 18" sub internally in series has benefits. In a club system if the DJ overdrives the system you will only ever blow 1 of those 2 sub drivers as the series circuit will open up saving the other driver. If you wire the box internally in parallel and overdrive the box, you will almost always blow both drivers.
People are confused when they start to calculate because they use a single(!) driver as a starting point, and so cannot understand from where +6dB go. When we take a connection in series, and compare to a connection in parallel, then everything will match
But with the same impedance in the amplifier both series and parallel has the same +3dB effect. Example__ Think an amplifier that is capable of delivering 64W at 4ohms. So that we drive 2 speakers with 2 ohm each by series way, so that each speaker will get 32W. We have two such speakers, therefore we get +3dB as doubling the power adds 3dB to the loudness. And by that same amplifier, we are running two 8ohm speaker in parallel mode. Then the impedance will be the same 4ohm. Each speaker will get 32W. In this situation also we are getting +3dB due to the previous mentioned rule. Note: only lowering the impedance and getting doubled power by the amplifier only increases 6dB.
I know I'm dumb on this issue, but please sum it up. Is it safe and better on the amp and speakers in each arrangement? Which would produce better sound? Does the phase change in series?
I don't get it. With a single speaker you get 20W of power. In the parallel case, you get 2 speakers outputting 20W each, giving a total of 40W. That's a 2x, or 3dB increase in power. I still don't understand where the extra 3dB comes from.
The extra 3db comes from doubling the acoustic energy from the second driver. Also, halving the impedance doubles the power only if the amplifier is perfectly linear (power doubles when impedance drops to half). Most amplifiers however do not produce double the power, in fact going from 4 to 2 ohms may produce less than 4 ohms and going to 2 ohms may even burn the entire amp if it's of poor quality.
You're getting double the effective driver cone area and it's enclosure, as well as a doubling of power as you stated. 3db from the additional driver and it alignment, and 3db from the additional power that driver is now consuming.
I'm not into SPL. Just good tone with best coverage for speaker, whether one or two or amount of ears listening. If a venue has capacity of 10,000 sets of ears and 10000 minds or 10000 bodies, how much power is needed in subpower for 1/2 of 10000 bodies in avenue that is designed for 10000 bodies. That seems more reasonable for life of any subwoofer. Using math to figure out impedance load is cool but in real world, a knowledgeable sound engineer needs to understand this in order to do a solid sounding show.
I don't get with your +3dB amp and +3dB acoustic power adding together resulting in a 3dB gain. The added electrical power powers the added transducer, and the added transducer produces sound. The 3dB gain is converted into 3dB acoustic power. The acoustic energy is just the electrical energy being transformed into acoustic energy using the transducer. You've said that the transducer doubles the acoustic energy, and I don't agree, it just transforms it. The +6dB comes from the definition. If I have a sub firing, let's assume it produces a monopolar radiation, then this simple model spits out the pressure : P = μ0*Σ*ω^2*X_eff /4π with X_eff being the efficient displacement of the membrane, Σ the surface of the loudspeaker and μ0 the magnetic constant. Then by adding another sub it's the same formula, but replacing Σ by 2 * Σ. thus adding 20 * log(2) from the definition of SPL : SPL = 10 * log(acoustic power/ref_acoustic_power) = 20 * log(P/P_reference). And 20 * log(2) = 6.021 something. The discrepency between the +3dB POWER and the +6dB PRESSURE is that acoustic pressure is related to acoustic power by a square law. Please challenge me if I'm wrong, this has made me crazy over the last few days, I can't sleep lol.
3dB from amp and 3dB from additional speaker (in parallel) will be 6dB total increase. The usual confusion is over why there would be 3dB more from the amp in parallel with the addition of a second speaker, but 3dB less from the amp when in series. Was this the thing you were referring to?
@@devinlsheets_alphasound yeah that's exactly my point. The 3dB added from the amp are transformed by the transducer, thus there is no "+3dB" from the additional sub. The +3dB from the additional sub comes from the amp. Saying "+3dB" because there is another sub means that this energy comes from nothing, which is not physically possible.
@@devinlsheets_alphasound the thing I'm referring to is a french pdf by Brouchier, you can find it online. What you're looking for is at page 52, but it's in french...
@@dbzlouis the thing is, the mic reads a 6dB increase when the second sub gets plugged in in parallel. Basically, that’s the starting point and then the question is: where does it come from? For example, you could imagine doubling the power to just one speaker. What would happen then?
Okay I think i got it. First, as a side note you didn't tell us how the dB measurement you're calculating is calculated! Sometimes there is a mismatch between the 10log(energy) and the 20log(pressure) formula and people mess up. But I think your db meter is not the cause, the real cause is the placement of the mic. At 0:54 I can see that your mic is in the air, so when you add another sub you have the sub + the reflexion of the sub. I think if you'd run the same test, but with the mic on the floor, you would not have than extra +3dB. EDIT : I'm wrong, since even with the reflexion you also double the acoustical power, since the original sub is also being reflected
it looks like your power amplifier is not strong enough. the output is that small. maybe the result will be different if it is made 4 ohm maybe the output will increase again
![Blox Fruits Dragon Rework Update [Full Stream]](http://i.ytimg.com/vi/EqDAp8udhm0/mqdefault.jpg)
This is the kind of audio content we need on RUclips. Very informative.
Eskimos have been hooking their woofers up in series parallel configurations for hundreds of years.
most brilliant analogy possible
But the result is "mush!" 😂
@@naturalveritiesuh
I did not see that one coming 🙏🤭
😂
Great video was taught this on a Rockford Fosgate amplifier and system design course 30yrs ago, first time seen such good explination of it :)
Easily one of the best video’s regarding this subject I’ce ever seen, keep the good stuff coming 👌🏼
What determines whether two signals of equal amplitude combine to produce a 6dB gain or a 3dB gain in signal level (voltage or SPL, but not power), is the “correlation” of the signals at the point of combining.
FULL CORRELATION CASE:
If the correlation is 100% between the two source signals at the location where the combined signal is being measured (the two source signals are received with identical amplitude and with identical phase) then a 6dB gain in level (SPL or voltage, but not power) is achieved.
Example 1: Two side by side subwoofers which are both fed the same signal (with the same amplitude and same phase) and which are both equal distant from the measuring device. In this case, the measurement device will measure a “combined” signal which is 6dB higher in SPL than that measure by either subwoofer alone.
For a sine wave signal source, the two source signals would always have their sine wave peaks “synchronized” and always providing a doubling of peak level. And we know that a doubling of level (voltage or SPL) results in a level gain of 6dB. However, it is important to note that the “power” delivered to the room is only 3 dB higher than that delivered by either subwoofer alone (a doubling of power results in a gain of 3 dB).
NO CORRELATION CASE:
If there is no correlation between two non-identical, but equal amplitude, signals at the location where the combined signal is being measure, then a 3dB gain in level (SPL or voltage) is achieved.
Example 2: Two side by side subwoofers are fed pink noise signals generated from two different noise generators (the pink noise signals are not correlated). In this case, the measurement device will measure a “combined” signal which is 3dB higher in SPL than that measure by either subwoofer alone.
The two signal’s peaks and valleys will only be in alignment part of the time. And over time, the signal alignment of the peaks will vary between in phase (0 degrees) and out of phase (180 degrees). And the average increase in SPL or Voltage signal level achieved will be 3db higher than that delivered by either subwoofer alone.
MAINTAINING 100% CORRELATION ISNT ALWAYS EASY
Even in example 1 above, if the SPL meter where to move around the room, the path length from each subwoofer to the measurement device would change differently for each subwoofer, and the correlation between the two signals being combined would not stay at 100%. The axis of the room where the measurement device is equidistant from the two subwoofer will always receive the 6db gain in SPL. But there will be some locations in the room where the path length from each subwoofer would result in a 180 degree phase shift at the measurement device, and the signal would be cancelled. But most people, who are not equidistant from both subwoofers would experience a 3 dB gain in SPL.
Another interesting example is the case where two signals of varying phase are combined.
Example 3: Two side by side subwoofers are fed sine wave signals from two different signal generators (one at 60 Hz and one at 61 Hz). In this case, the measurement device will measure a “combined” signal which varies in SPL reading over each one second period. For one instant in each one second period, the measurement device will measure a “combined” signal which is 6dB higher in SPL than that measure by either subwoofer alone. But AVERAGED over the full second period, the measurement device will measure a “combined” signal which is 3dB higher in SPL than that measure by either subwoofer alone.
In summary, achieving a 6DB gain in SPL with two subwoofers only occurs where the resulting phase difference between the two identical subwoofer signals at the measurement position is near zero degrees.
Very good video! Reiterating old knowledge and this was perfect, thank you.
Nice job, many thanks! Fascinating to see those frequency related impedance spikes. Great charts and hands on measurements.
Nice explanation of parallel vs series wiring with visual examples! I think anyone studying electronics or amateur radio should check out this video.
Nicely done!
Lol 😂..... amateur radio ?? Wtf ..😵💫
@@janinapalmer8368 Yep. Parallel and series circuits are on all three tests. This video is a perfect illustration the differences.
@alphasound just came across this video, it’s the first one I can find that demystifies this debate, great stuff!
So far, the best video I've watched in the 36hrs I've been trying to understand about speakers. I have these 5.1 speakers I found in our basement with it's player already disposed of that I want to use as a pc speaker, and I'm trying to learn how I can install them when there's just one front and one rear 3.5mm headphone/speaker jack, though it's got a sound card that supports up to 7.1, for the life of me, I have never been interested in electrical wirings until now. I don't how I can wire them all into one jack, or do I need to install another sound card with more ports, or buy some whatnot to connect them to. If they get more expensive than buying a pc speaker, they're going back to where they came from, useless.
I'm going to follow you from now on and learn.
36 hrs.? get some sleep, trust me, it's not that exciting and rather simple to learn - make it last cause after slew rate and damping factor there is not much on the horizon.
🎯 Key points for quick navigation:
00:00 *🔌 Introduction to Speaker Wiring*
- The video introduces the concepts of speaker wiring configurations: parallel and series.
- Explains the upcoming experiments with volume and impedance.
- Sets the stage for learning through real-time demonstrations.
00:28 *🎚️ Demonstrating Parallel Connection*
- The first experiment shows how connecting a subwoofer in parallel affects volume and current.
- Demonstrates a 6dB increase in microphone reading with parallel wiring.
- Current from the amplifier doubles while voltage remains constant.
02:19 *📊 Understanding Ohms and Current*
- Discusses the relationship between speaker impedance, current, and voltage.
- Describes how impedance affects amplifier load and current output.
- Introduces Ohm's Law and its relevance to audio systems.
04:04 *🔄 Effects of Series Connection*
- Demonstrates the impact of connecting speakers in series on volume and current.
- Shows that series connection results in a 0dB change in microphone reading.
- Discusses the division of voltage and current between the speakers.
06:04 *⚖️ Limitations of Series and Parallel Wiring*
- Compares the advantages and limitations of series versus parallel configurations.
- Emphasizes the resistance changes with frequency and its effect on performance.
- Notes practical limits of speaker configurations in parallel and series setups.
08:00 *🎶 Impedance Measurement and Efficiency*
- Explores the impedance characteristics of speakers across different frequencies.
- Highlights the importance of driver and enclosure compatibility for optimal performance.
- Concludes with a summary of the video’s main points and encourages further exploration.
Made with HARPA AI
Depends if they're acoustically coupled (coherent). If so, pressure adds and you get 6dB. If not, power adds and you get 3dB.
exactly, try this again at 15khz 30ft away and see what you get
I agree, two speakers outputting 20 Watts each is 40 Watts total, but speakers in unison do not add sound pressure levels linearly, they just push more air in parallel but at the same loudness. So dB in sound pressure does not always double when two speakers are driving the same signal at the same power level compared to one speaker doing the same. Take your stereo for example. You hear a tone pan from the left to center to right. When in the center, the sound is not louder, it is just balanced and sounds like it is from the middle. Each ear is hearing about the same volume level (just slight delays due to distance and echos in the room) but the sound from both speakers don't add up (in a perfect acoustical dead room) they just sound fuller. With head phones, you can get a wider separation but less fuller because each ear hears only one speaker for the most part. This is why there is a sweet spot in your stereo room where the sounds balance out to about what you get from headphones. Stereo recordings are designed for the left channel for the left ear and the right channel for the right ear. So in your stereo room - which should be acoustically dead, the sweet spot has no echos from the room and the program (music) can be listened to as it was intended.
At the 4:59 mark, with ONE speaker, you've got:
V=20V
I=1A
R=16ohm
This doesn't follow ohms law. Since the speaker resistance is set at 16ohms (perhaps slight variation considering it is a non ohmic device), it would not draw 1A of current, it would only draw the current required to keep ohms law intact. Please correct me if I'm wrong... From that time stamp onwards, there are similar errors carried through
the important question is dB relative to what and measured where?
Nice! This, along with many of your other lessons and demonstrations, should be mandatory study requirements for all "Audio People", especially live performance types!!! Most of them are clueless and believe myths of their predecessors, urban legends, hearsay and of course: "that's the way it is, everybody knows that!"
So when do I make a follow up video explaining that the terms “doubling” and “halving” aren’t totally accurate. They’re better than 99% accurate but to be precise, the increase is 1.995x not exactly 2x. Does anybody care?
@@devinlsheets_alphasound Only the boys using 200 foot 18 AWG wire wire runs to 4 paralleled Subs, because, they like precision 😂
I so agree....
It should also be noted there are some practical considerations that need to be taken into account when doing things like this. When you let an amp drive a one or two ohm load, you're beating the crap out of it. Playing music through a system isn't the same as taking measurements on a test bench. Also, you have to consider distortion. The harder an amp works, the more it distorts. Its unavoidable, and the amount of distortion an amp produces is directly related to how well its made. 2 power amps may be rated for the same amount of output in watts/ohms, but one may have half the distortion, and in the real world, that would make it a much more powerful amplifier.
I see in a lot of the comments, people seem to think they will be "loosing power" if they don't lower a speakers resistance so the amp puts out its rated full power at one or two ohms. Lowering resistance forces the amp into a situation where it has to work harder to deliver the same amount of performance than a speaker that is less demanding to drive, like one that drops no further than 5 or 6 ohms. The practical solution in a situation like this is to turn the volume up. That's why its better to present the amp with a speaker that's easy to drive in the first place. It leaves you with the freedom turn the volume up without fear that you will damage your amp or speakers.
Just to be clear, from what I could tell, everything covered in the video appears to be accurate. Nothing is wrong with the content. My concern is things were left out. Most likely there will be a future video covering the issues I raised above. So my advice would be to wait for future videos covering the rest of the topic before making any purchase decisions.
Wrong on a few points.
When you raise the amplifier by 6dB it makes output voltage doubled (20V to 40 V) , and current flow also doubled as manner (1A to 2A).calculating the (P) power it show 4 times increment as this: 20V x 1A =20W and 40V x2A= 80W. Clearly 80W means 4times like 20W.
But when you attached additional speaker it only cost more current, but no voltage increases, resulting power = 20V x 2A = 40W.
My question is, why the measurement mic showing 6dB same increment at both testings above, while the amplifier produce completely different power output as, 40w vs 80W.
I'm not into SPL. Just good tone with best coverage for speaker, whether one or two or amount of ears listening. If a venue has capacity of 10,000 sets of ears and 10000 minds or 10000 bodies, how much power is needed in subpower for 1/2 of 10000 bodies in avenue that is designed for 10000 bodies. That seems more reasonable for life of any subwoofer. Using math to figure out impedance load is cool but in real world, a knowledgeable sound engineer needs to understand this in order to do a solid sounding show.
@@rgortega1285Most (sound engineers? are selectively deaf (notch filter damage in their hearing range). I walk out of so many concerts that i've quite going. When is their mommy going to tell them the truth?
ohhhhhh 6 db+ so is this why they say is better to double the speakers instead of the power first??? more cone area vs more power?
Incredible clear explanation, thanks buddy !
Thanks!
I still don't get it. Doubling the power on one subwoofer results in a 3dB gain. But the same power split on two speakers suddenly should gain an additional 3dB so 6dB total? How can 3dB magically appear out of nowhere? Where is this "acoustic energy" supposed to come from?
100W to 8ohm = 200W to 4ohm if the amplifier can handle it. So not the same power.
There is only 3dB more of total energy being produced. But in certain sweet spots, such as right in front of the subs, the phases will be aligned, the wavefronts will add together, and you'll hear a 6dB increase. In other locations, such as off to the side, the wavefronts will be out of phase, destructively interfere, and you'll hear much less than a 3dB increase (maybe even negative, depending on the frequency and the distance between the subs).
@@kornielsen9471 Partially true, the standing waves effect you described is already counted for in the +3db. Standing waves can be negated by placing multiple subwoofers asymmetrically in the room (Dr. Earl Geddes's thesis).
@@dingdong2103 I am not referring to standing waves, which complicate things even more. Outdoors (with no standing waves), if you are exactly equal distance from both subs, you will hear a 6dB increase when you turn on the second sub. In other locations, it will depend on the frequency and distance delta, but the average will be a 3dB increase.
@@kornielsen9471 What you refer to is exactly what standing waves do in a room, summing and canceling of signal... Outdoors there will be just 2 clean signals. And the summing of signals only happens if the two drivers are within a wavelength of eachothers.
So if i were to use 4x 8ohm 15" Woofers in Parallel, what would the Ohmage then be?
And by adding any other speakers (8ohm) (but not woofers), does this have any (negative) impact
That would effectively be 32ohms. If you have an amp that can handle that, go for it. You can add more speakers if you wish, but keep in mind the impedance will also go up, and you might end up working your amps so hard that they die. A good practice would be to match your amp impedance if possible, that would be either by connecting your speakers in a series/parallel connection or getting more amps for your speakers if you have the budget
Extremely educational just came across your channel.
Exactly what I was looking for all this type of information
Thanks for sharing BUT NOW what if you got 4 12inch speakers in one guitar cabinet and the are factory wired in Series/ Parallel...how does that read on amp output? Thanks again.
If they all are 8ohm it would read 8 ohms. If they are 4 ohm it would read 4 ohms, 16 ohms-16ohms.👍🤗😉🫣
The Best info I've taken in since trying to understand thanks
What it is two separated active sub ?
+3db ?
I dont understand when you say +3dB acoustic power. Because the power produced by the added membrane, is the exact additional power transmitted by the amp. So why do you count it twice ? (+6dB)
With two separate active subs, you would expect a 6dB increase from the second sub being added, because behind that second sub is also 3dB more power from an additional amp.
If you double your cone area you double the efficiency that each cones can turn the motion of the cone into sound waves in air. It is a very lossy process. In other words both cones now produce twice as much sound as they normally would on their own. Like paddling a canoe with a broom stick vs a paddle - you exert the same amount of energy with both but you go twice as fast with the wider paddle because it can transmit your energy into the fluid water with greater efficiency.
But what if amp would work in lower than 2 ohms. Why I can't connect 10 subs in parralel, because amp will rip ?
The issue is not just the nominal impedance of each speaker, it is also the absolute minimum impedance at a certain frequency. As we saw in this video, the graph of impedance by frequency for a given speaker has peaks and troughs. So with music containing a particular frequency at a high level, a frequency which corresponds to a very low trough on the impedance graph, the current in the amplifier could increase beyond what its circuits can handle, thermally speaking.
On a side note: that hum coming from sub has an interesting effect of "robotizing" voice when speeding up or slowing down video's playback speed.
The king of AUdio is here!!! SUbscribed in 15seconds!! :) Love it man!! YOu rocks!!
There is no such thing as "3 dB more from the speaker".
The amount of available power is what voltage*current shows - period.
What you are demonstrating with "3 dB more from the speaker", is actually a coherent speaker array. Try moving your meas mic up and down and you see that the +6 dB isn't consistent.
Also if you switch the polarity of the second speaker, when in parallel configuration, you see that the measurement from the front drops dramatically, as the phase fronts from two speakers are cancelling each other.
Thx for this comment. I got a big questionmark in my mind how he got 4 times more acoustic energy bei doubling the amp output...
True. And let's not confuse the amp output power increase with the SPL increase: two connected but different things.
thanks !
Speaker output is rated as: SPL, Sound Pressure Level. Power, in Watts, is: P=EI, power equals Voltage times Current. And and real work, in a motor, or speaker coil winding, is performed by: Current. You can have a lot of voltage, but if there isn't a closed circuit, with current going through a circuit, there is no, "work," being performed. Such as a wall outlet, with nothing hooked up. Speaker output is usually expressed in dB, decibels, & measured by placing the speaker in an anechoic chamber, with an input of a tone of: 2.83 volts, & a mic pointed at them, one meter away. With an input impedance of 8 ohms, this is about one amp. My Klipsch speakers are about 98 dB efficient; they produce 98 dB of sound output, a listenable level. Other quality speakers produce: 88 dB, about 10 dB less. 3 Db = twice the power; 10 dB = ten times the power. If voltage is constant, ten times the current, power.
Great video as always! I like that you don't just do the calculations, you measure things. In physics measurements are king. If your theory disagrees with measurements the theory is wrong.
But I have an issue with this. What if you put 10 speakers in series? Your amplifier would output tenth of the power but you'd still get the same audio power. How?
Let's complicate things even more. Now you connect 10 sets of these to the same amplifier in parallel. Your amplifier outputs the same amount of power as it did when driving just one subwoofer. Same voltage and the same current. Same power. But the audio power just went up by 20 dB.
Let's have another thought experiment. You have 100 speakers. You connect all of them in series. Your amplifier outputs 1% of the power it was outputting with just one speaker but the audio power remans the same. You just increased the efficiency of the whole system by 100 times..
What if you had a 1000 speakers? Would your efficiency be 1000 times better? At what point your system's efficiency would be more than 100%? At what point would the system be outputting more energy than it's getting?
This is why there are “part 2” videos on the internet lol
He made a mistake in his calculations, see Elkin Velásquez Cuítiva comment.
There was indeed an error with that slide, I edited that part out with RUclips Studio.
So can you add 2 outputs of the same channel on same amplifier to double the output power? My amplifier has 2 cg
Channels and each channel has 2 outputs. I wandered to combine the output on each channel so I ended up with 2 outputs instead of 4.
With subs, you will max out acoustic efficiency somewhere around 30% depending on design. Meaning that your +6 db for every doubling of speakers starts to drop off and level off to +3 db. That should happen somewhere around 12 double 18" cabinets where you have reached maximum acoustic efficiency of the design and there is no more efficiency increase to gain by increasing cone area. Same with running speakers in series, you would reach a maximum volume and then start dropping off as the new speakers coming on line wouldn't be adding to the acoustic efficiency as maximum has already been reached and would also be physically far from the measurement location as you can't stack boxes in the same space of each other (damn Pauli exclusion principle).
At the 3:45 mark, I take exception to the idea that the second speaker adds 3db to the sould level. In a parellel arrangement, adding a second speaker doesn't change the voltage, current, or power going to the first speaker. Adding a second speaker doubles the amount of audio power produced (+3db). The load on the amplifier has doubled requiring twice as much current. Not only does this follow ohm's law, but also obeys the conservation of energy.
To get a 6db gain, you'd have to also double the power consumed and produced by each speaker. But that didn't happen! The voltage and current are the same and therefore so is the power per speaker.
The overall gain is only 3db. So, why did the test microphone measure a 6db gain?
Right, good question. What if you just doubled the current going to the first speaker alone? Then what would the microphone read?
Of course this breaks ohms law, because you couldn’t double only the current and keep the voltage the same, but what you could do is increase the voltage and current each by 1.4 which would effectively double the power, which is the same thing. So in this case, we would get 3dB yes? And if so, if you split that power between two speakers instead of one, you’d have the 3dB from the doubling of power, but then also another 3dB from the doubling of speakers.
It's because its 6dB at a certain point in space. on average, you get +3dB. See for the formulas. If you double the acoustic intensity, you add 3dB. If you double the acoustic pressure, you get +6dB. He should have explained with formulas.
I'm with you on that. The law of conservation of energy is pretty clear. You don't get something for nothing.
It's because most of that power isn't being transferred into sound, it's being wasted. You are not creating energy from nothing by adding boxes, it's already there, just not being utilized. Your speaker cone, being a solid, is high impedance and the air, being a compressible fluid, is low impedance. When you put a high impedance load into a low impedance load, well over 90% of your energy is wasted, sometimes as much as 99.9%. Most of the air just gets moved off to the side and eventually that motion ends up as heat and not sound. When you add another speaker, you double your cone area. That doubling of cone area doubles the efficiency of converting motion into sound of the whole system. That's where the second +3 db comes from, the increase in TOTAL system efficiency. Every time you double your speakers, you double your efficiency UNTIL you reach the maximum system efficiency possible and then that "free" +3 db's is no longer there. For direct radiator boxes (sealed, vented) that is about 25% maximum efficiency, horns can get you up to 50% total efficiency. So you get +6db's for every doubling of boxes until you reach that maximum efficiency, and then you only get +3db's after that for each doubling. Note that high frequencies will reach that maximum efficiency limit with fewer boxes then the lower frequencies. So when you double your box count you may get +6db's from say 20-55hz but only +3db's from 60-100hz because those higher frequencies may already be at their maximum. For horns you need about 8 boxes (subwoofers) to get to the maximum, for regular speakers you would need closer to 20 (double 18" ers) to get to their maximum efficiency, after that, no more +6, you only get +3.
Is it true that if you have 2 speakers and one speaker can handle more power than the other, the that speaker will take the extra power? So if you had a 10 watt speaker and a hundred watt speaker and a 100 watt amplifier you wouldnt blow the 10 watt speaker cause the 100 watt speaker would take the extra power.
I don't think so. If the speakers are of the same impedance, they will divide the power equally, and so I expect the 10 watt speaker will blow at high output levels.
Normally, we handle speakers of different power ratings by only sending high frequencies to the lower rated speaker, via a crossover network, because most of the energy is in the lower frequencies of music. The half-way point for division of power in music is around 120Hz as I recall, just above subwoofer range.
Two full-range speakers of different impedances could be a different matter.
I have a question, that answer I cannot find anywhere. I have a pair of 4 Ohm speakers and a pair of 8 ohm speakers. My integrated amp had a typical 8 jacks for connecting 4 speakers. The A is 4ohm-8ohm, and the B speaker slot is 8-16 and the A+B asks for all 8 ohms. Since I dont have 2 pairs of 8 ohm speakers, so can I somehow connect the 4 Ohm speakers at the same time with 8 ohm without damaging the 4 ohm speakers, as I understood that in case of connecting all 4 speakers they should be all 8 ohm?
Is the sound at the end taken by microphone? My subs got much quieter with increased impedance in the test during the last minute of this video, but the commentary then said that the volume was consistent during the sweep
Best explanation I have come across
For such weight just 50kg the L18 is brutal. thanks for such comparison!!!
As an RC car enthusiast, this is particularly confusing. We run batteries in series and parallel. Series combines the voltage (way more power!), parallel combines the mah (way more time to play, think of it as making your gas tank twice as big). Is it the same principle with speakers, because it seems to be the exact opposite? And to make things more confusing, both the amp and the speakers can change impedance depending on dual channel or stereo setup. So if we were to compare this to an RC car battery setup….is the speaker the battery, or is the amp the battery? On a side note, what happens to these setups you just showed, if the amp is in mono mode? Meaning can you run 2 speakers in series/parallel through a mono setup? And what would that do? You seem to have a strong grasp of this topic, any insight is appreciated. 👍
Great video. Do these rules apply to powered subs? I have the Yamaha DXS 18XLF powered subs. When I couple them together do I get +3 or +6 db gain?
In the case of self-powered equipment, the couplings are not a problem, since each box has an amplifier for itself, and therefore there are no impedance additions or subtractions.
So what you were saying ( in a very roundabout sort of way ....) was by hooking up two 16ohm drivers in series makes no difference.... only half the output power gets delivered but I assume the decrease in radiation resistance makes up for this .... am I right ?
I like this video, I am new with speakers. I think there is an error at 5:31, the 8 ohm on left below the amp should be 16 ohm? Also, I would think you would want to measure things with one speaker at one volume level, then while measuring, turn up the volume to get 3db increase and see how much voltage and current are needed. Then you have a response curve to test against the equations. Maybe I missed that but seemed like you were keeping at same volume knob level setting the whole time.
When you connect two speakers in parallel, you double the amount of current which doubles the ohms. The voltage remains the same.
So if you use 2 8ohm drivers in you dubbel 18'' sub woofer. and you wanna use 2 cabinets on one side on the amplifier. then you need to wire the speakers in serie?
Awesome testing. Thank you
What is going to hapen if we plug two pairs of 8ohm woofers but one pair is paraller and the other one in seriers to the first one? Will the resistance be the same as if we have just one woofer? And the output still be doubled? Or the output will cancel itself as well?
Thats why we tune port to free air fs of a woofer to compoansate for the high resistance on the impedance curve to even it out?
How do you have the meter leads on?
I tried using a normal meter to test for voltage coming out of my car subwoofer amp, which obviously takes in 12-14v and i get weird numbers
Use ac voltage on your dmm. Use a sine wave test signal to test for voltage, using music will get you readings all over the place.
Is that a bandpass type enclosure? I notice 2 nulls in the impedance curve.
It's quite interesting to see how using more speakers saves energy. Although I'd expect this to gradually taper off as you add more and more speakers, so maybe you'd only get 5 dB from 2 more subwoofers.
It doesn't "save" energy. The amount of energy being output from the amp more or less stays the same but the acoustic output changes. Adding an extra driver adds 3db of output and halving the resistance ads another 3db of output but the current also changes.
@@SilentShadow-ss5xp yes but if you want to listen at the same level it saves power. The example is illustrated best with the two series woofers that were the same level with half the current.
@@TimpBizkit Half the current EACH one, because they split the same amount of current that flows. In total is the same, so no savings, plus the cost of second driver equals spending more, not saving more :)
@@BOB-eb8xz but two series woofers have double the impedance. So half the current and the same voltage flows to the pair equals half the power to the two woofers that are as loud as one. The current doesn't split in two lines because it's a series setup - one "river" of current = same current to each woofer as total but voltage is split.
Each woofer in a pair gets a quarter of the power (half the current and half the voltage). You will need more money for drivers and wood but less for an amp (and in big builds alternator and eventually fuel consumption, although the double box is heavier to move around).
If you think about it, two speakers are a bigger "boat oar" on the air around them and thus convert power to sound better.
@@TimpBizkit wouldn't the best idea be keep the current the same just use woofer no.2 as a passive Radiator? Especially if the enclosures tuned correctly 🤔
I am looking to run 6 Bass. Is using 3 amps in mono, and connecting the othe 3 to the speakers better than running 2 per amp?. Try to make it powerful and cost effective.
6 Bass amps would be to expensive at this point.
I appreciate your channel. Thank you.
I would say 6 db (if by doubling of loudspeakers each loudspeaker gets his own amplifierpower.) am I correct?
Can u make a video with 4 4ohm woofers wired to 4 ohm... im trying to improve my studio lab sl-550.... but im in need of more information....
missing the parallel and serial connection mixed
Sehr gute Erklärung. Danke!
Sorry but I have doubts :
Series 16+16=32ohms : the amp produces same voltage and half the current, hence -3dB. Each speaker gets half the voltage (-3dB) and half the current (-3dB), therefore each speaker -6dB. Since there are 2 of them, the total acoustic output is -3dB (half the power).
Parallel 16&16=8ohms :
The amp produces same voltage but twice the current (+3dB).
Each speaker gets same voltage (0dB) and same current as only one (0dB). Since there are 2 of them, the total acoustic output is +3dB (twice the power).
Putting an infinite number of speakers in series will finally translate into 0 power, since the voltage at each speaker and the current will both tend to zero, or am I really really wrong ?
Voltage and current are both a part of one single equation. Voltage/Resistance=Current. If you lower voltage, current naturally follows. What you're doing is that you're basically saying that Four apples + Six oranges equals Ten fruits. Then remove Three oranges. Now you have Four apples + Three Oranges which equals Seven fruits. You don't say that you have Three fewer oranges AND Three fewer fruits all in all which is now a grand total of Six fewer fruits, do you?
@@Turntablist11 dunno about your fruit analogy, but as long as the amp behaves like a constant voltage source, my reasoning is right. Just try putting 10 speakers in series on a solid state amp and you will hear very little overall acoustic power.
@@paolozak3014 I just realized that I read your first comment wrong.
What you are forgetting about though, is sensitivity. You gain 3db sensitivity when you double the amount of subs. This is true as long as you haven’t reached maximum sensitivity yet, which is around 100db (baffle gain, resonances, diffraction gain, and boundary gain not included).
Two subs in parallel is 3db more sensitivity plus 3db current, so 6db in total.
Two subs in series is 3db more sensitivity minus 3db current, so 0db in total.
@@Turntablist11 sorry but I can’t follow your sensitivity argument.
Series : the amp delivers half the current & same voltage. Each sub gets half the voltage (-3dB, in series the voltage is divided) and half the current (-3dB), so each sub is at -6dB (1/4 of the power). Since there are 2 of them, in total we have -3dB (half the power).
Parallel : the amp delivers twice the current & same voltage. Each sub gets half the current (1/2 of twice = 1) and same voltage, hence 0dB (no power loss). Since there are 2 subs, we have +3dB in total (twice the power).
@@paolozak3014 Loud, low, small. Pick two. That’s the basics of speaker design. A small loudspeaker that plays low frequencies will not be loud. Make it larger and it will be louder. When you double the amount of speakers, you gain more sensitivity, equal to about 3db.
@devinlsheets_alphasound - I'm super curious about running things in series. Theoretically, if I had multiple four 4-ohm subs with a 1000w rms rating and a 135dB half-space spl, and wanted to run two of them in series per channel so I could get away with fewer/cheaper amplifiers, how would I calculate the wattage rating to properly drive them? Can I double the recommended wattage like with a parallel configuration to see a +3dB increase in SPL over one cabinet for a pair in series? Is it a lost cause because of the inherent electrical and mechanical cancellations? If i do get amplification in a series deployment, would I see +6dB if I doubled that same configuration? Are there phase/output issues or other substantive issues that I'm failing to consider?
If you use powered subs to simplify the whole process, a lot more people will understand it. Basically doubling your speakers gives you +3db . If one sub max SPL is 135db, adding an extra sub would make it 138 db SPL Max, and to increase it another 3 DB you have to add two more subs, the four subs would produce 141db Max SPL and if you want to add another 3 db, you have to have eight subs to increase it to 144db SPL Max. Basically, you have to double the speakers for every 3 db increase you want in SPL.
OK but you're also doubling the amplifier power when you add another powered sub, so...
@@devinlsheets_alphasound yes you're correct but I was just explaining the fact that if people want to get more SPL out of their system, they have to double their speakers for every 3db increase. If they use four passive subs instead of two, they will probably have to use two amplifiers to power them to get the additional 3db increase.
Unless your amplifier is already completely out of available power, adding a second subwoofer in parallel will automatically draw double the power from the amplifier, resulting in a total of 6 dB increase in your system when you add the second subwoofer. If you could theoretically keep the amplifier power the same all around through some artificial means, adding a second speaker would increase it by 3 dB.
With - correlated signals - self-powered subwoofers yield 6 dB more pressure for each doubling of loudspeakers as opposed to 3 dB.
@@MerlijnvanVeen i'm curious, what situations involve doubling loudspeakers but only yielding 3dB?
Parallel cost more speaker wire than series connection, basically parallel is way better than series is that right Sir?
Good effort and thanks a lot for the Video. I would like to experiment like you did, but hardly find opportunities with gears. To whatever I have learnt: Doubling the Voltage or current should result in 6 dB not 3 dB. Correct the video @3:24. Doubling Power results in 3dB change.
Please correct me if I am wrong.
What happens when you turn it up to 11?
Btw good detailed content, thanks for taking the time to share.
If i have 2 speaker 800w to 4 ohms if in series connection what is the watts of the speaker thank you
shouldnt the series connection be 20v at 0,5amp = 10watts? so 5watts for speaker (10v at 0,5amps)? you said 20watts, 10w each speaker
Yeah I made a mistake lol working too quickly late at night
btw I edited that part out with RUclips Studio just now
Thank you for impedance response from nexo bandpass
I've seen all the internet about this issue and this is the best explanation of all. I'm really impressed! But 3:44 you say that one more sub gives you +6db. Are you sure? I thought it would give you another 3db, not 6, so together they would make +6db and not +9db. Do I get it right?
That’s because you can’t add that second sub in parallel without also doubling the amplifier power, it just happens automatically
@@devinlsheets_alphasound I appreciate you answer but my question remains unanswered. Sorry, my English is not perfect and I might have not made myself clear enough. The problem is mathematics. If one sub gives +3db, another sub should give another +3db, which would make +6 db all together. What I Understand from you video at 3:44 is that one sub adds +3db but another sub adds +6db which all together makes + 9db. Which is correct? Does the extra sub give +3db or +6db? Because the picture is confusing to me. Thank you
@@paul7000 we’re only asking what the addition of a second speaker is to the equation, whatever SPL the first speaker is already providing is a given
@@devinlsheets_alphasound If one sub gives +3db, do two same subs give +6db or +9db? Assuming that we feed them with same RMS.
@@paul7000 one subs doesn’t give 3dB, it gives whatever dB you run it at, which depends on how big your amplifier is and how close you are to it. It might be 3, or 93, who knows. Adding the second speaker (and doubling the power) will add another 6dB to whatever dB the first speaker was putting out. If it was 3, then it’ll be 9 total. If it was 93, then it’ll be 99 total.
Don't forget with multiple drivers in a cabinet you can wire series/parallel meaning if all drivers are the same impedance then total impedance at socket is as one driver. All 8 ohms then total 8 ohms .my vintage Bose 802s are all in series with a 0.9 impedance per driver do you get anything from 7to 8 ohms
What about car audio where DVC subs come into play?
I suddenly Have a problem connecting front door speakers 2 a second channel makes really bad audio( IV had the sound system in the car for 4 years I was told it was either a bad rca cable or the input of the RCA was damaged, I used another amplifier and changed the RCA cable but I still have the bad audio
I ended up connecting all four speakers to one channel parallel and now the audio is ok out of all 4 speakers in total the 4 speakers add up to 24 ohm speakers watts add up to just under 1900 watts and the amplifier is 3000 watts I'm wondering if this is safe until I can finally get the problem fixed by a professional the gain on the amplifier is not max it's around half maybe less not sure since it's just a cross that I twist left or right
Nice Honda Clarity. Love mine
Great explanation, thanks!!!
Solid state amplifiers are rated at different speaker impedances. So my bass amp puts out 500 watts at 4 ohms, but only 350 watts at 8 ohms.
I can use two 8 ohm speakers in parallel to achieve 4 ohms, or if there was 2 ohm speakers, two of those in series.
It’s not the series or parallel connection that matters, it’s the total speaker load on the amp.
Current is what destroys amplifiers and speakers. More current equals more heat equals magic smoke.
Look.... An ideal Amplifier with 350 Watts at 8 Ohm should give 700 Watts at 4 Ohms, Like the KRELL Amplifiers do. Because of internal resistance of your Amplifier, he is not able to double the Current, that is why he only do 500 Watts at 4 Ohm :-)
If they’re wired in parallel it will go up 3db. If they were in the same cabinet, and the cabinet was the proper size it would go up 6db. If those speakers are wired in series you’ll drop 3db. Ohms is a measurement of amperage, while volts is a measurement of Electromotive Force. But who cares?without getting crazy you can think of these two measurements this way. If you have a garden hose with water flowing through it, the volume if water coming out is its Amperage. The pressure of the water coming out is akin to voltage.
you should make a reaction video and demonstrate this
Error is on 5:36.The power when connected in series is 10 watts
There was indeed an error with that slide, I edited that part out with RUclips Studio.
does lower impedance produce lower frequency sounds?
I asked since i noticed speakers wired in parallel produce more bass than speakers wired in series. thank you
Devin, any idea why Nexo uses 16 Ohms drivers in their S-118 subs?
Nope. But maybe I’ll ask and see what they say!
probably so you can run a shitload of them in parallel to a single amp
Also, and that's speculation, higher impedance speakers use thinner and lighter wire on the coil, so, you may have a tighter magnetic gap and lighter voice coil, thus a better speaker overall
@@victoramicci840 It will also produce less heat.
Greater speaker impedance means greater damping factor with a given amplifier. You may also use thinner cables for each speaker. Also you may have more speakers per channel as someone has already mentioned. You need a strong amp though. Nexo 4x4 is one monster amp.
That way you can hook up 4 subs (parallel) and have the amp see a total of 4 Ohms. If you have an amp that can drive 2 Ohms, you can hook up 8 subs.
Actionable intelligence, I love it!
very nice video, but I have some corrections and contributions
1) 6:20, while it is true DC resistance of voice coils, do vary with frequency, it is a very little change in comparison with reactance, which varies greatly. The text should say "impedance varies with frequency", which is not the same of resistance. But all of these varies with frequency, resistance, reactance and impedance overall. (ideally resistors have a flat frequency response, but complex AC circuits like speakers are very complicated and do exhibit non flat resistance component)
2) 3:34, I think what you tried to explain here is right, but not correctly explained.
The dB scale for power is calculated as P (dB) = 10 * log10(P/Pref)
While dB scale for pressure and voltage is calculated as V (dB) = 20 * log10(V/Vref)
These formulae means that doubling the power is to add +3dB of power, but doubling the current, voltage or presure is adding +6dB of the quantity.
That said, what really happens when you connect a second speaker in parallel with the first, while remaining a constant signal or voltage output, it is true the amplifier delivers +3dB of power, because it is doubling its power output, its impedance load is divided by two, thus power is multiplied by two, because of P = V²/Z . Where V remains the same and Z gets divided by two. Doubling the power is adding +3dB of power. Say for example if your first spkr is developing 1 Watt, the second spkr you connect will develop the same 1 Watt, while the power of the first one remains unaltered. Being the total power delivered by the amp just the double of just one speaker connected.
But with SPL pressure is a different story.
While signal/voltage V remains the same, the power of the first spkr will remain the same, and the second will develop the same power of the first.
You have +6dB of SPL pressure output, because the pressure is multiplied by two , these pressures of every spkr is just added. and the dB scale for pressure is different that the scale used for power. Double the sound pressure (say in Pa units) will result in adding +6dB to the SPL.
So why you have +3dB power in the amplifier and +6dB pressure at the spkrs?, why this 3dB difference?
Because doubling the amount of speakers raise +3dB of the sensitivity of the system.
Say for example one spkr has a sensitivity of 95 dB 1Watt/1meter, two speakers have 98dB 1Watt/1Meter. But this is far more complex because there are issues like vector sum, phase coherence, wavefront shape, polar response and many things that make this very complicated in practice.
Nice ok so: adding a second speaker in parallel but sharing 1W of power raises the total sensitivity by 3dB as measured by the microphone. So then, what if we also double the total power to 2W? The mic measurement goes up another 3dB, for a total of +6dB. If we double the power going to only one speaker, the mic reading only goes up 3dB. So what is the mic measuring?
@@devinlsheets_alphasound
"adding a second speaker in parallel but sharing 1W of power raises the total sensitivity by 3dB as measured by the microphone. So then, what if we also double the total power to 2W? The mic measurement goes up another 3dB, for a total of +6dB." Yes, correct.
" If we double the power going to only one speaker, the mic reading only goes up 3dB. So what is the mic measuring?" Assuming you disconnected the second spkr, and have only one, if you double the power (+3dB of power), you get +3dB of pressure. while doing this you multiply speaker voltage by 1.4142 (square root of two)
the mic measures pressure, voltage reading of microphone terminals are proportional to pressure waves at the mic capsule, say for example a calibrated measurement mic could say its sensitivity is 1 Pa = 94dB SPL = 8.15 mV RMS.
Pressure reference for the dB SPL scale is 20 uPa (twenty micro pascals) as in formula dB SPL = 20*log(P/Pref)
Because power is proportional to the square of either voltage or current, the 10*log formula was chosen for power, and 20*log for voltage, current, and pressure that is proportional to spkr voltage.
That way when you add +3 dB or +whatever dB to power, you get equal +dB to voltage or pressure.
that means, adding +3dB of power (doubling power), you get +3dB at SPL pressure (pressure/voltage is multiplied by 1.4142 square root of two)
Adding +6dB of power (multiplying power by four), you get +6dB at SPL pressure (pressure/voltage is mutiplied by two)
Or in other words, if you multiply voltage by two, power will be multiplied by four, because power is proportional to square of voltage.
You have to consider the Amplifier's impedance output as well.
Let me use 8 Ohm speakers because many amps have 2, 4, 8, or 16 Ohm outputs.
All Voltage, Current and Watts are RMS in my discusssion.
4 Ohm Output: Two 8 Ohm speakers in parallel = 4 Ohms (impedance match), at 40 Watts: In this case the Amplifier will supply 40 Watts. 12.649 Volts out with each speaker drawing 1.582 Amps each = 20 Watts from each speaker for 40 Watts total.
4 Ohm Output: Two 8 Ohm speakers in series = 16 Ohms (impedance mismatch), at 40 Watts: In this case the Amplifier COULD supply 40 Watts but it can't. 12.649 Volts out but only 6.325 Volts get to each speaker drawing 0.791 Amps each = 5 Watts from each speaker for 10 Watts total.
Since -3dB is roughly a 50% Power Loss, 40 Watts to 20 Watts is -3dB, and 20 Watts to 10 Watts is another -3dB for a total of -6dB (1/4 the Power).
So even if the Amplifier COULD try to put out 40 Watts with two 8 Ohms speakers in series on a 4 Ohm output, it can't do that due to the impedance missmatch.
This is why Amplifers usually have several impedance outputs. Since two 8 Ohms speakers in series is 16 Ohms, you should switch to the 16 Ohms Output (if the Amplifier has one):
16 Ohm Output: Two 8 Ohm speakers in series = 16 Ohms (impedance match), at 40 Watts: In this case the Amplifer will supply 40 Watts but now using a different voltage. 24.298 Volts out but only 12.649 Volts get to each speaker drawing 1.582 Amps each = 20 Watts from each speaker for 40 Watts total.
So If you change the Speaker arrangement and not select the proper amp Output Impedance, you will get less power out of the Amplifier or you may overload the Amplifier and cause damage. So ALWAYS match the Amplifier's Output Impedance to the Overall Speaker Cabinet Impdeance.
Examples:
One 12 Inch Speaker at 100W at 8 Ohms = Cabinet 8 Ohms 100 Watts RMS (commonly used)
Two 12 Inch Speakers at 100W at 8 Ohms in Series = Cabinet 16 Ohms 200 Watts RMS (less commonly used)
Two 12 Inch Speakers at 100W at 8 Ohms in parallel = Cabinet 4 Ohms 200 Watts RMS (commonly used)
Four 12 Inch Speakers at 100W at 8 Ohms in Series = Cabinet 32 Ohms 400 Watts RMS (Outputs for 32 Ohms are rare, not commonly used)
Four 12 Inch Speakers at 100W at 8 Ohms in parallel = Cabinet 2 Ohms 400 Watts RMS (less commonly used)
Four 12 Inch Speakers at 100W at 8 Ohms in Series/parallel = Cabinet 8 Ohms 400 Watts RMS (commonly used)
Series/Parallel Arrangement of four 8 Ohm Speakers 100 Watts each arranged for 8 Ohms 400 Watts total:
|
-------
| |
8 Ohm 8 Ohm
| |
-------
| |
8 Ohm 8 Ohm
| |
-------
|
So why are there 2, 4, 8, or 16 Ohm speakers? The lower the Impedance (ohms) of the speaker, a lower Voltage is required to drive it BUT LESS AMPS (current) is needed as well.
Since current (Amps) is key is power distribution (think of High Voltage power lines), a 2 Ohm Speaker (or Cabinet) requires less current though the wires to get the power from the Amplifer to the Speakers. At home or small venues, 8 Ohms is fine, but in a large arena where the Speakers are up high and many feet away from the Amplifiers, 2 Ohm Speakers and Cabinets are better.
Series/Parallel Arrangement of four 2 Ohm Speakers 100 Watts each arranged for 2 Ohms 400 Watts total:
This Speaker Cabinet requres less current to drive the speakers and thus less current/resistance (IR) losses though the cables.
Also, lower current cables can be of a thinner gauge which saves weight and cost.
|
-------
| |
2 Ohm 2 Ohm
| |
-------
| |
2 Ohm 2 Ohm
| |
-------
|
In the video 1 amp drives 1 speaker 1A 20v 16 ohm, so 20 watts. Does that mean when connecting 8 speakers in series with acoustic coupling the amp only draws 2.5 watts while having similar acoustical output as 1 speaker? 😮 Because 1 speaker: 20V 1A 16ohm = 20 watts. 2 speakers: 20V 0.5A 32 ohm= 10 watts, 4 speakers: 20V 0.25A 64ohm = 5 watts, 8 speakers: 20V 0.125A 128ohm = 2.5 watts. I know 128ohm could be high for an amp, but this is about understanding the theory. Using 4 ohm drivers would result in 32 ohm load in the same 8 speaker set up.
Or to get deeper into it: 2 speakers in parallel would result increase +6db. Meaning having a big array of 32 speakers in parallel would increase the acoustical output by a massive +30db! I am thinking of building a compact line array system with a 3 inch driver delivering 104dB > so max SPL of a 32 speaker line-array system would deliver 134dB am I right?
Here's something I always wanted to know:-
You build two subwoofer boxes with two 18 inch 8 ohm speakers each. You wire both speakers in both boxes in series. That would mean both boxes would be playing at 16 ohms. If you were to then 'daisy chain' both boxes together at the speakon connectors, would they then both be playing at 8 ohms or at 16 ohms?
If you wire each 8ohm speaker in a box in series, that would increase the impedance to 16ohms per box. If you then daisy chain(parallel connection) each boxes, that would lower the impedance to 8ohms.
@@ThaKingRyan thank you. That's all I wanted to know.
@@glenprovidence4769 glad to be of help
The added benefit of doing what you say in say a club is that if you overdrive those boxes wired in series internally, you will only ever blow 1 of the two drivers as as soon as 1 blows, the series circuit opens up saving the other driver. If you wire the boxes internally in parallel, you will most likely blow both drivers if you overdrive them. This is a huge consideration when designing a club system for DJ's etc to use. The cost difference between replacing half vs all the sub drivers can be astounding.
@@wally7856 I know.
so, parallel divided curent, series divided voltage. parallel increase SPL uses more power, series do not increase SPL but saves power 🤔
once again. great content, 👏👏👏👏 you guys should have 1M of views not like others that all they do is play their favorite songs but have 1Ms of views... people are so pathetic. 🤦♂️
Now do a comparison between listed max SPL output compared to real world output.
Awesome explanation.
I am about to go from 1 18" Resilient Sounds platinum to 2 18" in my truck. I will also be going from one Down4Sound JP23v2 to 2, or one per sub wired at 1 ohms for a total of 5600 watts I hope to get 6 dbs or slightly more, because of acoustic coupling because the 2 subs will be right next to each other, literally 1 inch apart.
I see there is diminishing returns for every subwoofer after the the second (amp/sub). The SPL calculator has +6.0, +3.5, +2.5, 2.0 db and so on. I'm almost finished building two vented boxes each with a 24" subwoofer tuned for 23 hz (internal volume 11 excluding ports, bracing, driver). This is for an outdoor audio/concert setup. Reinforces the fact on how important the sensitivity and frequency response of a subwoofer or driver is. It can get incredibly expensive or consume a ton of electricity.
Yes, because our sense of SPL is logarithmic, not linear, so it takes exponentially more power or number of subwoofers to increase things equally in proportion each time according to our sensitivity to SPL. If you have one sub, adding another will “sound” about the same amount of increase proportionally as having 50 and adding 50 more.
Horn loading is the way to go if you really want to push big SPL at sub frequencies. Tapped horns are very effective.
@@dingdong2103 how do you determine the box? Hornresp? The videos on RUclips look like pro audio clones but it's obvious the driver parameters are important after using WinISP.
@@stiffmeister0hYeah Yes hornresp is an excellent tool. I built a few tapped horns with 21" 18Sound drivers and the actual response was dead on as predicted. +-3db from 80 to 20hz room response in a mid size cinema. System pushes easily 130db clean and punchy bass.
@@dingdong2103 well I have a third 24" sub that is currently in a box with four 12" passive radiators (Earthquake PUMP-12x2). Unfortunately, I did not brace the box enough and it vibrates. I'm going to dig in and see if the braces came loose plus figure out resonant frequency of the radiators. However, having the driver out will allow me to play with hornresp. I just recently learned of horn resp while building these behemoth vented boxes. The 15 cf external dimensions are just enough if not too much. Recommended 16 cf internal and holy cow too much space.
If you run a series parallel circiit you could hook up 100 speakers to the same amp and have the same ohm load as just one of the speakers.
Only coils in dvc subs should ever be wired in series. I would never, ever wire separate subs in series. Just asking for trouble.
Yes but wiring say a double 18" sub internally in series has benefits. In a club system if the DJ overdrives the system you will only ever blow 1 of those 2 sub drivers as the series circuit will open up saving the other driver. If you wire the box internally in parallel and overdrive the box, you will almost always blow both drivers.
Great video!
Thank you, sir Information. and Details.
very helpful, thank you very very much!
People are confused when they start to calculate because they use a single(!) driver as a starting point, and so cannot understand from where +6dB go. When we take a connection in series, and compare to a connection in parallel, then everything will match
But with the same impedance in the amplifier both series and parallel has the same +3dB effect.
Example__
Think an amplifier that is capable of delivering 64W at 4ohms. So that we drive 2 speakers with 2 ohm each by series way, so that each speaker will get 32W. We have two such speakers, therefore we get +3dB as doubling the power adds 3dB to the loudness.
And by that same amplifier, we are running two 8ohm speaker in parallel mode. Then the impedance will be the same 4ohm. Each speaker will get 32W. In this situation also we are getting +3dB due to the previous mentioned rule.
Note: only lowering the impedance and getting doubled power by the amplifier only increases 6dB.
My driver impedance 2 ohm each in serialized by 3.5 swg
I know I'm dumb on this issue, but please sum it up. Is it safe and better on the amp and speakers in each arrangement? Which would produce better sound? Does the phase change in series?
I don't get it. With a single speaker you get 20W of power. In the parallel case, you get 2 speakers outputting 20W each, giving a total of 40W. That's a 2x, or 3dB increase in power. I still don't understand where the extra 3dB comes from.
The extra 3db comes from doubling the acoustic energy from the second driver. Also, halving the impedance doubles the power only if the amplifier is perfectly linear (power doubles when impedance drops to half). Most amplifiers however do not produce double the power, in fact going from 4 to 2 ohms may produce less than 4 ohms and going to 2 ohms may even burn the entire amp if it's of poor quality.
You're getting double the effective driver cone area and it's enclosure, as well as a doubling of power as you stated. 3db from the additional driver and it alignment, and 3db from the additional power that driver is now consuming.
I'm not into SPL. Just good tone with best coverage for speaker, whether one or two or amount of ears listening. If a venue has capacity of 10,000 sets of ears and 10000 minds or 10000 bodies, how much power is needed in subpower for 1/2 of 10000 bodies in avenue that is designed for 10000 bodies. That seems more reasonable for life of any subwoofer. Using math to figure out impedance load is cool but in real world, a knowledgeable sound engineer needs to understand this in order to do a solid sounding show.
3dB is double. Correct?
Depends what you're comparing!
This is another advantage to having amplified subwoofers. You can keep adding parallel service without worrying about resistance or output loss
Great video.
I don't get with your +3dB amp and +3dB acoustic power adding together resulting in a 3dB gain.
The added electrical power powers the added transducer, and the added transducer produces sound. The 3dB gain is converted into 3dB acoustic power. The acoustic energy is just the electrical energy being transformed into acoustic energy using the transducer. You've said that the transducer doubles the acoustic energy, and I don't agree, it just transforms it.
The +6dB comes from the definition. If I have a sub firing, let's assume it produces a monopolar radiation, then this simple model spits out the pressure : P = μ0*Σ*ω^2*X_eff /4π with X_eff being the efficient displacement of the membrane, Σ the surface of the loudspeaker and μ0 the magnetic constant. Then by adding another sub it's the same formula, but replacing Σ by 2 * Σ. thus adding 20 * log(2) from the definition of SPL : SPL = 10 * log(acoustic power/ref_acoustic_power) = 20 * log(P/P_reference). And 20 * log(2) = 6.021 something. The discrepency between the +3dB POWER and the +6dB PRESSURE is that acoustic pressure is related to acoustic power by a square law.
Please challenge me if I'm wrong, this has made me crazy over the last few days, I can't sleep lol.
3dB from amp and 3dB from additional speaker (in parallel) will be 6dB total increase. The usual confusion is over why there would be 3dB more from the amp in parallel with the addition of a second speaker, but 3dB less from the amp when in series. Was this the thing you were referring to?
@@devinlsheets_alphasound yeah that's exactly my point. The 3dB added from the amp are transformed by the transducer, thus there is no "+3dB" from the additional sub. The +3dB from the additional sub comes from the amp. Saying "+3dB" because there is another sub means that this energy comes from nothing, which is not physically possible.
@@devinlsheets_alphasound the thing I'm referring to is a french pdf by Brouchier, you can find it online. What you're looking for is at page 52, but it's in french...
@@dbzlouis the thing is, the mic reads a 6dB increase when the second sub gets plugged in in parallel. Basically, that’s the starting point and then the question is: where does it come from?
For example, you could imagine doubling the power to just one speaker. What would happen then?
Okay I think i got it.
First, as a side note you didn't tell us how the dB measurement you're calculating is calculated! Sometimes there is a mismatch between the 10log(energy) and the 20log(pressure) formula and people mess up.
But I think your db meter is not the cause, the real cause is the placement of the mic. At 0:54 I can see that your mic is in the air, so when you add another sub you have the sub + the reflexion of the sub. I think if you'd run the same test, but with the mic on the floor, you would not have than extra +3dB.
EDIT : I'm wrong, since even with the reflexion you also double the acoustical power, since the original sub is also being reflected
very nice video ! thx
No sense at the end what is good Parallel or Series ??????????????????????
parallel is louder, but increasing number of speakers lowers impedance, which shouldn't go below 2ohms (can damage amp).
it looks like your power amplifier is not strong enough. the output is that small. maybe the result will be different if it is made 4 ohm maybe the output will increase again