With no connection to the diaphragm this is definitely an "electret" speaker, not an electrostatic speaker. This type of speaker uses a static charge impregnated into the diaphragm. Electrets make pretty decent microphones, but are pretty well regarded as the dumpster version of an electrostatic speaker. The fabric-like construction of the driver itself reminds me of the commercial E-Stat sheets made by Warwick Audio Technologies, except the WAT sheets are single sided (only one grid).
Of course, that makes sense. I knew that's how electret mics worked, but had no idea you could make speakers from them. They definitely market them as electrostatics - "treVolo 2 uses the same electrostatic technology that is typically reserved for high-end speaker systems." Makes sense they are the lower quality than proper electrostatics, and I note consideration distortion, even though once again they claim low distortion as a feature of these.
@@EEVblog Just like about everything, you can use things in reverse, and it often doesn't make a good version of that. Just like a speaker makes a horrible microphone.
I have a pair of Stax eletret headphones, they require an amplifier to drive them through a speaker output and sound amazing. Saying they're "dumpster" versions of electrostatic sounds like the way audiophiles talk where they'll denegrate everything that isn't what they consider the best. Somehow there being something incredibly expensive means that everything else is a trash fire.
@Stephen Morton I have high quality audio gear but do not buy into snake oil products.....so am I an audiophile I wonder! I hate compressed lossy codecs, so maybe that qualifies me as one? :-p
BenQ Sent me a pair of these and the wooden stands to review on my Audio Channel. The build is amazing but they are certainly a far cry from a full tilt electrostatic. Im glad you gave me the guts so I didn't have to look inside myself. I will definitely mention this tear down when I do my video.
A few thoughts. As noted by others. These are elecret electrostatics. That still makes them electrostatics. Electret refers to the way the charge is impregnated into the diaphragm. Nothing more. In general the problem with electrets has been that the diaphram material needs to be a bit thicker than you can get away with if you are externally supplying the bias. So you get the same problem with microphones, electret microphones tend to not be as good as those that provide a bias voltage to the diaphragm. As to passive radiators. They work identically to ports. They are a mass on a spring, which is what a pipe full of air looks like. The advantage of a passive radiator is that you can get combinations of mass and spring that would require a port of silly size. So they are an obvious design component in small speaker boxes. Passive radiators and ports take over the lion's share of bass radiation at low frequencies and can add a very significant amount of bass capability. Capability that importantly includes bass loudness that the speaker driver alone could not produce without exceeding its excursion limits. Any EE will be happy modelling speaker boxes - there is a direct translation from the physical parameters of speakers, the box, port/passive-radiator to capacitance inductance and resistance. So much so that it is easy to usefully model a real life speaker design in Spice. A point about panel speakers in general. They are dipole radiators. This of course means that they intrinsically can't reproduce sound with wavelengths much larger than themselves, as the sound wave cancels out around the speaker. But the rear radiation of sound gets energy into the reverberant space of your room, something conventional speakers are not so good at doing at higher frequencies. This can be very beneficial. Full size panel radiators or di-pole speakers can be set up to work in a room and manage the mess of reverberant versus direct sound to advantage. Not so much these little speakers, but there will be no doubt that the energy radiated off the back of the panels will have an influence on the sound, and especially the range of listening positions where they can sound good. Someone put a lot of effort into this little speaker design. However I am suspicious that those cross pattern spacers were a late add on to cope with problems in the speaker, and that they are the reason the panels have such a poor low end frequency response. It smells like the intent was for the panels to go much lower - maybe down to 500Hz, and there were problems that were band-aided late in the piece.
Well Dave I have to say, I think you should consider doing a few more 'reviews' like this. There are very few reviewers that will show the design, QA, attention to detail that you do. Really good to see Benq stepping up and going the extra mile.
Forgive me but the rubber pads are not to keep the electro static drivers from going "thud" against the unit, those are to keep the metal shroud from vibrating and causing noise. I bet $20 the rubber screw covers are to prevent the speakers from going "thud"
I think it might be using a pre-charged diaphgragm, making it an electret. Stax made some old electrets back in the day but they're universally considered to be worse than their real electrostatic headphones.
I bought Stax SR-5 headphones with the SRD-7 transformer back in the 70's and still use them all the time to this day. They are still in amazing shape. They have great presence to their sound quality. It was a great investment especially how long they are lasting :)
@@mr.bennett108 I've heard they were really bad and they measure like crap too. See: diyaudioheaven.wordpress.com/headphones/measurements/mitchell-johnson-jp1-dj/
I've got a pair of Superex PEP-74 headphones, which use the same drivers as the Stax SR-5, and they're pretty nice. They're not great, but they're on par with my Audio Technica AD900X.
18:53 I don’t think you can necessarily infer the transformer turns ratio from the resistances. Typically used thicker wire for the low turns primary to keep the current high and thin wire with higher unit length resistance for the secondary.
True, but that just means turns ratio will be even higher, because they probably filled 1 layer with the primary winding, and then the secondary side is hundreds of layers ( probably bunch wound to get the interwinding capacitance down, like any CCFL transformer is, which is what I suspect these are) of spider thread. Would be interesting to find some large CCFL inverter transformers ( probably old big screen TV with 2 CCFL tubes) and try them out with an electrostatic speaker and see if they perform as good as the ultra expensive custom wound ones normally used.
Dave is not really inferring the specific number of turns from resistance but rather confirming a rough magnitude in the ratio. Consider a rather fine #40 gauge secondary, even at that fine a gauge you will need around 1000 feet (300m) to achieve 1K-ohm resistance and, in a small transformer, it does not take a lot of guesswork to infer from that that there are thousands of turns to achieve 1.5K-Ohms (IIRC - or whatever the final resistance was).
I have been using my Trevolo S as a DAC speaker on my laptop since I did my review. Has been excellent, Yes sound somes out of the back and front. I didn't tear mine down yet as I didn't have a small enough torx.
The color still looks off (very green and muted) at the mailbag desk bit. You definitely need to do some color correcting. (If you still haven't hooked up all the lights, just ignore me.)
@@EEVblog "This is Unwatchable!" how could you not employ a Hollywood editing team. Your videos need to have perfect color correction! It isn't just a youtube video where people should ignore this kind of stuff, it should be shot/edited like a box office cinema movie! The quality is so Q3 2018.
And those are passive radiators (equivalent of a port). What we used to call ABRs (Auxiliary bass radiator) in the UK. With a bit of DSP EQ these might be able to produce a bit of bass.
Nice tear-down mate! The Simpson 260's on the shelf behind you made me reminisce about the days of yore. I had a beautiful 260-8P. She drove a fancy black 00248 Roll Top Bakelite Case. Man I miss her...
Same type of no-HV drivers that I had in some ES headphones back in the '80's.... and they were amazing... absolutely passive headphones with just a dual step-up transformer box between the amplifier speaker outputs and the headphones.
Could be an Electret diaphram, no need of biasing. AKG got a headphone with this trick with transformers integrated inside, which could be driven directly by a power amplifier.
Normally the grid should be very stiff to avoid any modulation in audio frequency, in Sennheiser Orpheus 2 they even used gold plated ceramic as grid. Dunno if theres some magic going on...
@@simontay4851 I swear the vid was longer just now, but an advert kicked in when I tried skip through, and then it showed the shorter time. I think it just means that Dave used RUclips's editing function to trim the vid.
Gosh I haven't been to this channel in a while. It's good to be back. Last video I saw was the one when he was holding his new born. I don't know how many years it has been. I'm going to keep watching to see if he brings him on again.
Dave maybe you can use these speakers as a recording tool. If you re-record all your speech through the Bluetooth speaker without the tweeters, then it would be much more pleasant!
Would just need one of the spectrum analysers that go below 9kHz, almost any electret insert, a CR2032 coin cell, a 1k resistor and a 100n mylar coupling capacitor to make a non calibrated relative analyser. Think you could get that together without even looking hard in the dumpster room, one old PC and one phone will do the lot, plus a blob of hot glue to hold it all together on some sort of stand.
It's just an idea, but IS the dialectric carrying a load at all? What if it relies on purely electric movement of the plates due to the coulomb forces? If so, the sound produced would have roughly a double pitch (frequency doubled) but since it is digitally processed, it could easily be compensated in the DSP! You could feed the waveform into a seperate speaker/amplifier (analog) to test that. Or you could compare the inputsignal if there is an analog aux input to the drive signal. Anyway, I am curious to find out if it is that or using a loaded diaphragm like an electret. Success with your magnificent channel!
That's really a nice little speaker system. Thanks for sharing, EEVblog. :-) It's bass setup reminds me of years ago when a friend gave me a couple of ESS Technologies speakers. They were big heavy-constructed real wood cabinets with a huge thick metal tweeter horn at the top front-panel and below that was a 6 or 8 inch mid-range driver and a 12 inch diameter passive bass diaphragm on the back of those speakers. The original driver and passive woofer's foam supports had all disintegrated, so I took the drivers and passive woofers out and replaced them with a similar-sized driver for the front and a 12 inch regular speaker on the back, with no connections to it's voice coil terminals. It only gets moved by the changes in air-pressures developed by the driver on the front The cabinets were totally air-tight and those things sounded so friggin' awesome it's insane. The bass would thunder out of those cabinets loud and clear, along with the mids and highs, and yet the cones of the driver and passive woofer barely wiggled....it was kinda eerie ..lol :-D... Incredible yet simple technology ... a retroactive WTG @ESS for those awesome speakers way back when, and WTG now @BenQ for your Trevolo S Electrostatic bluetooth speaker system.
The lower frequency bound of the electrostatic panels can be calculated by the shortest dimension of the electrostatic panels. Judging by the visual dimensions of this, the woofers in this thing are going to take over in the 300-400 Hz range.
Sagan may be able to hear the hi frequencies better. those cost around £250 so glad you got it back together ok, 18r play time, 3D with stereo and party modes.I suppose the bass needs some volume to move the air around those side ports
I believe it's 2 different names ... Phillips with double l's developed the cross point screw, and Philips is the Dutch electronics former megacompany. That tape... I have what seems to be exactly the same. It sticks great and is super strong, but the adhesive dries out after some years.
Looks like good build quality but nothing of it suggest hi-fidelity to be honest. Considering the audio processing, once you start reprocessing to make something sound better there is no hi-fi in it. In hi-fi i would look for garbage in and garbage out perfectly. the ability to reproduce exactly what is put into it. DSPs always are there to produce something different than what is put into it.
So they built a giant capacitor that exploits the movement of the plates when charging and discharging, creating sounds? The same effect can be heard when ceramic capacitors start squealing in PSUs
They have the SMT arrow so the operators know which end to feed into the SMT pick and place line. If you can have two rows, it's easiest to flip the rows 180 degrees across from each other so rotation of the panel doesn't matter. Maybe they couldn't do two rows?
Proper electrostatic speakers sound genuinely amazing. Much more realistic than standard speakers. But once you are at the >1000€ range, the conventional speakers are also extremely good.
I mean the whole bluetooth speaker thing is more about having something on the road/camping/beach/etc, not a system at home. Also did you test it with the ground connected?
I wonder if it sounds any different with the ground plane connected. Maybe it's an important thing in the design! Making one of the layers move more towards/away from the ground.
I've had Monsoon flat panel electrostatic speakers since 2003(ish) and they are no where near constructed like that and don't sound anything like that. They do have their own issues though. Not sure what they built there, but those aren't electrostatic speakers, they look like fakes.
Ah, the "SMT" *IS* appropriate! That main board appears to be TWO single-sided boards sandwiched together! (11:40), each would have been wave-soldered.
Building my own bt speaker for bicycle with PLS-P830986 and SLS-85S25CP04-04, not tested in projected enclosure jet, but have feeling it will be great for outdoor riding.
@5:12 I would be suspicious that those elongated speakers are the woofers, with the "speakers" on the front being nothing more than port baffles to effectively increase bass response... will find out if I'm right after you get that bit apart. EDIT I was almost right, it was the other way around...!
'Real' electrostatic speakers usually do just fine in any normal living room conditions. In the bathroom, they will rapidly go to shit because the membrane is incredibly thin. Condensation will ruin it.
Interesting video ! You could convert this into a portable electrostatic headphone amplifier by adding a self bias stage on the output of the center tapped transformers, as is done with the STAX SRD-6 self biasing driver unit (see schematic). Add a couple of caps, resistors and diodes and voilà. Would be a fun experiment.
Check out Martin Logans. A dream when I heard them was the top of the line. One of the oldest was Janzen in the 60's had a h.v. tube in the power supply.
You are confused... Philips (who used to make consumer electronics, you can still buy it but it is now just a label on equipment made by others) is not the same as Phillips of the screwdrivers and also not the same as the Phillips oil company. Note the single L in Philips and the double-L in Phillips.
Electrostatic, well at least Martin logan, need to fire sound forward and backward. Also a lot of definitive speakers use passive bass radiators, seems to work well with a nice big surface area for the sound to move it, not sure if useful for that small.
I don't own any, but... the theory is that having an entire vibrating surface changes the shape of the sound waves. The claim is they sound "larger" than a speaker box. You have to remember that some high end electrostatic speakers can be 5 feet tall (look up "Magnepan"). They've been around since the 60's. They can be very flat and compact. You could in theory hang them on a wall like a painting. Except they radiate backwards so it wouldn't sound very good. I think the biggest "advantage" for people is simply the novelty and cool factor.
A proper electrostatic mylar diaphragm has incredibly low mass compared to nearly all other speaker technologies. Driver mass, all other things being equal, is to speakers what mass is to cars. The lower the mass, the easier to accelerate. Make them large enough and they can move a lot of air with no mechanical elements. You can actually make them a full range driver if the panel is big enough, but it's expensive and they get VERY large to do that, so usually they require a subwoofer. Martin Logan usually has a large (transparent!) panel above an integrated sub. I've heard them in person and the high frequency reproduction is incredibly lifelike.
Normally, electrostatics benefit from having extremely thin and light membranes. That means they can reproduce high frequency sounds more accurately since the membrane is easier to control than dynamic (voice coil) speaker. They don't typically vibrate at amplitudes as high as dynamic speakers, so they generally are not great at producing low frequency sounds. That's why they are often supplemented with dynamic woofers.
It makes naive people think they're getting something special? An electrostatic tweeter (well, "ribbon tweeter" of various descriptions) can be excellent for stereo imaging, which is giving the illusion of sound coming from somewhere inbetween the two speakers. I'm talking mid to high end studio monitors, not so much this particular speaker.
I remember year ago, probably late 70’s Wireless World magazine did a project over many months on a DIY electro static headphones, that one could make, I never tried to may it my self, it seemed a way to DIY ETC myself.
+Gary Miles YES! It was Wireless World 1973 and my roommate at uni built a pair. They worked stupendously well. They looked lashed up of course, but the sound quality was phenomenal. Easily better than some quite expensive Sennheisers we used at uni at the time. The spatial field and high frequency response were truly amazing. I tried out some STAX electros of the day in a top audio store and I'd say the DIY ones sounded just as good ... I actually preferred the sound of the DIY ones.
Radfordperson Yes! My wife wouldn’t let me have them in the house - they looked like old fashioned electric convector heaters in a kind of off-gold colour. Needed to be rather large to get any sort of bass response.
+Radfordperson I'm just guessing from the name obviously but were/are you a Radford amp fan or even an ex employee? Be interested to know as I worked for Arthur in 1973/4 as a student engineer.
Hi Bob, you are correct, I have a very nice STA25 III, SC22 and FMT2. Amazing that you worked for Authur. I would be interested in any info available. I'm on pinkfishmedia as Radfordman. I used to know Jim Rogers.
I remember hearing a proper set of electrostatics a while back. Their were actually vintage floor speakers that used them as the tweeters, they sounded like modern speakers! It's too bad this is a poor example of them. Electrostatic speakers are still made for home audio.
Dave, how does the engineers on those projects always come up with those highly specialized chips? Like this Bluetooth chip, I bet I can't find it on Digikey or Google it. Are those engineers just highly specialized and keep up with what's going on with their applications, or are there companies specific for consulting on "where can I find the best chip for my project?"
The industrial designer looks to have cut their professional teeth on Sony equipment. Unfortunately the loudspeaker systems designer seems to have learned their trade at Amstrad in the late 1980s, and then had the last cent of cost beaten out of them in backstreet Shenzhen. Embedded electret sheet? That's incredibly low budget crap. I don't think Quad ESL have much to be afraid of.
That was absolutely splendid English. Moreover, the meaning was conveyed fully and succinctly. Just in case you are too young, or not from the UK. Amstrad were Alan Sugars attempt at building cheep as fuck electronics in the 1980s, packaged up in an effort to look half reasonable to anyone with little to no idea, or around 90% of the population. They were plastic silvery boxes, with basically fuck all in them but the most basic of components, usually the very minimum on one board, with the thinnest of wiring. An insult to electronics and design, especially quality audio. They were, in a word. SHITE!
I’m wondering if a low powered Cr 3032 battery powered audio player could play a stereo waveform that simulate a 50hertz ac sine wave and then stepped up and rectified to a usable power source. 🤔😯
Interesting...but £150 though.....I'd play with one for half that.... I did used to own a pair of Quad Electrostatics back in the day....wish i still had them today...
Dave! Where is the Triplett 630-NA???? There was a sad lonely empty space on the shelf where it once was. It's two brothers even looked sad. The whole time I was watching that video, I just couldn't quit wondering. It's totally my favorite multimeter, or excuse me, Volt-Ohm-Meter. Well, it's soon to be second favorite! Because I just ordered my 121GW from your webstore!!! YAY!!!! I'm soooooo excited. I've been wanting one like totally forever man! As soon as I get it, I'm going to do a review on my joke of a youtube channel that has now reached 6 whole subscribers! Now, it's possible that one of those subscribers might be my mom, but hey!
It's ashamed it's an elecltret speaker because otherwise it looks like a very well designed and constructed speaker that I'd consider buying if the price was right. OK after clicking the link in the description and seeing that they cost $299 there is no way in hell. In the $300 - $400 range you can buy the KMC3, Klipsch Music Center 3, Portable Bluetooth 2.1 speaker that puts out quite substantial bass for a 5" ported woofer. Crystal clear never a hint of distortion even at full blast. Peak rms 135 watts. Discontinued but findable still.
This kind of speakers never had amazing sound but what you heart was the transformer! Ferit core it's not for audio. You will not believe the deference in quality if you put iron core!
It demonstrates the main problem of electrostatic drivers: you get no bass. I have a pair of Hosiden DH-77 headphones, really flat, very 80s style, it has an excellent mid and high range and noooo bass. Must be an 80s thing, I bet they go amazing with synth music.
piezo electric i guess explains the transformer to step up and as well explain why there is no BIAS voltage. i do hope they DONT call it an esl since it is not !! distortion wise proable even worse then a common speaker
With no connection to the diaphragm this is definitely an "electret" speaker, not an electrostatic speaker. This type of speaker uses a static charge impregnated into the diaphragm. Electrets make pretty decent microphones, but are pretty well regarded as the dumpster version of an electrostatic speaker. The fabric-like construction of the driver itself reminds me of the commercial E-Stat sheets made by Warwick Audio Technologies, except the WAT sheets are single sided (only one grid).
Of course, that makes sense. I knew that's how electret mics worked, but had no idea you could make speakers from them. They definitely market them as electrostatics - "treVolo 2 uses the same electrostatic technology that is typically reserved for high-end speaker systems."
Makes sense they are the lower quality than proper electrostatics, and I note consideration distortion, even though once again they claim low distortion as a feature of these.
@@EEVblog Just like about everything, you can use things in reverse, and it often doesn't make a good version of that. Just like a speaker makes a horrible microphone.
I have a pair of Stax eletret headphones, they require an amplifier to drive them through a speaker output and sound amazing. Saying they're "dumpster" versions of electrostatic sounds like the way audiophiles talk where they'll denegrate everything that isn't what they consider the best. Somehow there being something incredibly expensive means that everything else is a trash fire.
@@EEVblog Almost like manufacturers make misleading claims to drive up sales.
@Stephen Morton I have high quality audio gear but do not buy into snake oil products.....so am I an audiophile I wonder! I hate compressed lossy codecs, so maybe that qualifies me as one? :-p
It's a noisy capacitor.
That's true an there are two noisy coils
lol
You said just what I was thinking when Dave described how electrostatic speakers work.
BenQ Sent me a pair of these and the wooden stands to review on my Audio Channel. The build is amazing but they are certainly a far cry from a full tilt electrostatic. Im glad you gave me the guts so I didn't have to look inside myself. I will definitely mention this tear down when I do my video.
Cool, thanks.
wild Z appears
Let us know when you have your audio review up! Cross-channel synergy!😁 Would love to hear what these sound like.
oh
@@MichaelBerthelsen the review is now up.
A few thoughts. As noted by others. These are elecret electrostatics. That still makes them electrostatics. Electret refers to the way the charge is impregnated into the diaphragm. Nothing more. In general the problem with electrets has been that the diaphram material needs to be a bit thicker than you can get away with if you are externally supplying the bias. So you get the same problem with microphones, electret microphones tend to not be as good as those that provide a bias voltage to the diaphragm.
As to passive radiators. They work identically to ports. They are a mass on a spring, which is what a pipe full of air looks like. The advantage of a passive radiator is that you can get combinations of mass and spring that would require a port of silly size. So they are an obvious design component in small speaker boxes. Passive radiators and ports take over the lion's share of bass radiation at low frequencies and can add a very significant amount of bass capability. Capability that importantly includes bass loudness that the speaker driver alone could not produce without exceeding its excursion limits.
Any EE will be happy modelling speaker boxes - there is a direct translation from the physical parameters of speakers, the box, port/passive-radiator to capacitance inductance and resistance. So much so that it is easy to usefully model a real life speaker design in Spice.
A point about panel speakers in general. They are dipole radiators. This of course means that they intrinsically can't reproduce sound with wavelengths much larger than themselves, as the sound wave cancels out around the speaker. But the rear radiation of sound gets energy into the reverberant space of your room, something conventional speakers are not so good at doing at higher frequencies. This can be very beneficial. Full size panel radiators or di-pole speakers can be set up to work in a room and manage the mess of reverberant versus direct sound to advantage. Not so much these little speakers, but there will be no doubt that the energy radiated off the back of the panels will have an influence on the sound, and especially the range of listening positions where they can sound good.
Someone put a lot of effort into this little speaker design. However I am suspicious that those cross pattern spacers were a late add on to cope with problems in the speaker, and that they are the reason the panels have such a poor low end frequency response. It smells like the intent was for the panels to go much lower - maybe down to 500Hz, and there were problems that were band-aided late in the piece.
Well Dave I have to say, I think you should consider doing a few more 'reviews' like this. There are very few reviewers that will show the design, QA, attention to detail that you do. Really good to see Benq stepping up and going the extra mile.
Forgive me but the rubber pads are not to keep the electro static drivers from going "thud" against the unit, those are to keep the metal shroud from vibrating and causing noise. I bet $20 the rubber screw covers are to prevent the speakers from going "thud"
Yep, you are right, my goof.
I've gotta say, starting the video and immediately having the "you call that a knife" moment to open a box has made my day.
I think it might be using a pre-charged diaphgragm, making it an electret. Stax made some old electrets back in the day but they're universally considered to be worse than their real electrostatic headphones.
I bought Stax SR-5 headphones with the SRD-7 transformer back in the 70's and still use them all the time to this day. They are still in amazing shape. They have great presence to their sound quality. It was a great investment especially how long they are lasting :)
Maybe they aren't the best but they're still very good compared to regular headphones, especially considering their age.
Mitchell and Johnson make a series of electret+cone headsets that are considered pretty OK
@@mr.bennett108 I've heard they were really bad and they measure like crap too. See:
diyaudioheaven.wordpress.com/headphones/measurements/mitchell-johnson-jp1-dj/
I've got a pair of Superex PEP-74 headphones, which use the same drivers as the Stax SR-5, and they're pretty nice. They're not great, but they're on par with my Audio Technica AD900X.
Quad in the UK and MartinLogan in Olathe, KS still make ESLs. They typically have an integrated amplifier since they need about 2kV to work.
18:53 I don’t think you can necessarily infer the transformer turns ratio from the resistances. Typically used thicker wire for the low turns primary to keep the current high and thin wire with higher unit length resistance for the secondary.
True, but that just means turns ratio will be even higher, because they probably filled 1 layer with the primary winding, and then the secondary side is hundreds of layers ( probably bunch wound to get the interwinding capacitance down, like any CCFL transformer is, which is what I suspect these are) of spider thread.
Would be interesting to find some large CCFL inverter transformers ( probably old big screen TV with 2 CCFL tubes) and try them out with an electrostatic speaker and see if they perform as good as the ultra expensive custom wound ones normally used.
Dave is not really inferring the specific number of turns from resistance but rather confirming a rough magnitude in the ratio. Consider a rather fine #40 gauge secondary, even at that fine a gauge you will need around 1000 feet (300m) to achieve 1K-ohm resistance and, in a small transformer, it does not take a lot of guesswork to infer from that that there are thousands of turns to achieve 1.5K-Ohms (IIRC - or whatever the final resistance was).
Not sure if BenQ was ready for such an elaborate teardown when they asked for the review. You revealed all their secrets :)
Thanks for the teardown Dave, good video! I always wanted to know how these things worked since I saw one in the '70s in an electronics store.
Transform the whiteboard into a speaker now!
I have been using my Trevolo S as a DAC speaker on my laptop since I did my review.
Has been excellent, Yes sound somes out of the back and front. I didn't tear mine down yet as I didn't have a small enough torx.
I saw a review of the "audio smile" speakers and I was wondering how they fit everything in such a small enclosure. Can't wait for the teardown!
"Maybe a destructive tear-down...Beautiful" at ~3:00 to ~3:10 is priceless. This is why I love watching your EEVblog.
You are measuring the DC resistance of the transformers, and get the turn ratio..... now that's something wrong!... whats with the sqrt(Lprim/Lsec)?
The color still looks off (very green and muted) at the mailbag desk bit. You definitely need to do some color correcting.
(If you still haven't hooked up all the lights, just ignore me.)
The actual colour temperature looks right to me. But yes, not all lights installed yet.
@@EEVblog "This is Unwatchable!" how could you not employ a Hollywood editing team. Your videos need to have perfect color correction! It isn't just a youtube video where people should ignore this kind of stuff, it should be shot/edited like a box office cinema movie! The quality is so Q3 2018.
@@xenonram, OMG... sooooo funny!
@@xenonram Many times, I wish that RUclips would include an "aspect ratio" control in their tools menu! I'm VERY sensitive to AR being off!
And those are passive radiators (equivalent of a port). What we used to call ABRs (Auxiliary bass radiator) in the UK. With a bit of DSP EQ these might be able to produce a bit of bass.
Nice tear-down mate! The Simpson 260's on the shelf behind you made me reminisce about the days of yore. I had a beautiful 260-8P. She drove a fancy black 00248 Roll Top Bakelite Case. Man I miss her...
Love these kind of consumer tear downs. Keep it up!
Same type of no-HV drivers that I had in some ES headphones back in the '80's.... and they were amazing... absolutely passive headphones with just a dual step-up transformer box between the amplifier speaker outputs and the headphones.
Could be an Electret diaphram, no need of biasing. AKG got a headphone with this trick with transformers integrated inside, which could be driven directly by a power amplifier.
Normally the grid should be very stiff to avoid any modulation in audio frequency, in Sennheiser Orpheus 2 they even used gold plated ceramic as grid. Dunno if theres some magic going on...
That black wires that not connected is for safety thing - if you suddenly break one of speaker ears it will protect audio wires from breaking.
At the 32:50 time mark there's a "hidden message" at the end of this video. Wacky !
Oops, editing mishap :D
The video is only 29:45 long.
@@simontay4851
I swear the vid was longer just now, but an advert kicked in when I tried skip through, and then it showed the shorter time.
I think it just means that Dave used RUclips's editing function to trim the vid.
@@simontay4851 yeah, because Dave fixed it.
@@simontay4851 Proof: bitchute dot com /video/HmwEh5P3D54/
Love how he's got the wiki page for electrostatics open when he's demoing the speaker.
Gosh I haven't been to this channel in a while. It's good to be back. Last video I saw was the one when he was holding his new born. I don't know how many years it has been. I'm going to keep watching to see if he brings him on again.
Dave maybe you can use these speakers as a recording tool. If you re-record all your speech through the Bluetooth speaker without the tweeters, then it would be much more pleasant!
You need to use a audio spectrum analyser to do speaker spectral comparisons
Meh, couldn't be bothered.
@@EEVblog couldn't be bothered seems to sum you up, unsuscibe
LOL goodbye then
Who cares? lol
They're not audiophile speakers, so really there's no point.
Would just need one of the spectrum analysers that go below 9kHz, almost any electret insert, a CR2032 coin cell, a 1k resistor and a 100n mylar coupling capacitor to make a non calibrated relative analyser. Think you could get that together without even looking hard in the dumpster room, one old PC and one phone will do the lot, plus a blob of hot glue to hold it all together on some sort of stand.
It's just an idea, but IS the dialectric carrying a load at all?
What if it relies on purely electric movement of the plates due to the coulomb forces?
If so, the sound produced would have roughly a double pitch (frequency doubled) but since it is digitally processed, it could easily be compensated in the DSP!
You could feed the waveform into a seperate speaker/amplifier (analog) to test that. Or you could compare the inputsignal if there is an analog aux input to the drive signal.
Anyway, I am curious to find out if it is that or using a loaded diaphragm like an electret.
Success with your magnificent channel!
That's really a nice little speaker system. Thanks for sharing, EEVblog. :-)
It's bass setup reminds me of years ago when a friend gave me a couple of ESS Technologies speakers. They were big heavy-constructed real wood cabinets with a huge thick metal tweeter horn at the top front-panel and below that was a 6 or 8 inch mid-range driver and a 12 inch diameter passive bass diaphragm on the back of those speakers. The original driver and passive woofer's foam supports had all disintegrated, so I took the drivers and passive woofers out and replaced them with a similar-sized driver for the front and a 12 inch regular speaker on the back, with no connections to it's voice coil terminals. It only gets moved by the changes in air-pressures developed by the driver on the front
The cabinets were totally air-tight and those things sounded so friggin' awesome it's insane. The bass would thunder out of those cabinets loud and clear, along with the mids and highs, and yet the cones of the driver and passive woofer barely wiggled....it was kinda eerie ..lol :-D... Incredible yet simple technology ... a retroactive WTG @ESS for those awesome speakers way back when, and WTG now @BenQ for your Trevolo S Electrostatic bluetooth speaker system.
The lower frequency bound of the electrostatic panels can be calculated by the shortest dimension of the electrostatic panels. Judging by the visual dimensions of this, the woofers in this thing are going to take over in the 300-400 Hz range.
Sagan may be able to hear the hi frequencies better. those cost around £250 so glad you got it back together ok, 18r play time, 3D with stereo and party modes.I suppose the bass needs some volume to move the air around those side ports
I believe it's 2 different names ... Phillips with double l's developed the cross point screw, and Philips is the Dutch electronics former megacompany.
That tape... I have what seems to be exactly the same. It sticks great and is super strong, but the adhesive dries out after some years.
Looks like good build quality but nothing of it suggest hi-fidelity to be honest. Considering the audio processing, once you start reprocessing to make something sound better there is no hi-fi in it. In hi-fi i would look for garbage in and garbage out perfectly. the ability to reproduce exactly what is put into it. DSPs always are there to produce something different than what is put into it.
MB D, Unfortunately, this is EXACTLY what they are doing. Their ears are tuned BETTER than yours, obviously. LOL
So they built a giant capacitor that exploits the movement of the plates when charging and discharging, creating sounds? The same effect can be heard when ceramic capacitors start squealing in PSUs
They have the SMT arrow so the operators know which end to feed into the SMT pick and place line. If you can have two rows, it's easiest to flip the rows 180 degrees across from each other so rotation of the panel doesn't matter. Maybe they couldn't do two rows?
Proper electrostatic speakers sound genuinely amazing. Much more realistic than standard speakers. But once you are at the >1000€ range, the conventional speakers are also extremely good.
I got some ceramic magnet drivers at Value Village. They are not big enough for a real stereo, but they are surprisingly responsive...
I mean the whole bluetooth speaker thing is more about having something on the road/camping/beach/etc, not a system at home. Also did you test it with the ground connected?
They sent you the kick starter speakers fully assembled. You should have gotten the kit.
my favorite technology for small speakers are soundmatters foxl. They have a very impressive bass system into a very small design.
I wonder if it sounds any different with the ground plane connected. Maybe it's an important thing in the design! Making one of the layers move more towards/away from the ground.
I've had Monsoon flat panel electrostatic speakers since 2003(ish) and they are no where near constructed like that and don't sound anything like that. They do have their own issues though. Not sure what they built there, but those aren't electrostatic speakers, they look like fakes.
Ah, the "SMT" *IS* appropriate! That main board appears to be TWO single-sided boards sandwiched together! (11:40), each would have been wave-soldered.
Those woofers look exacly like the drivers you find in bose soundlink mini bluetooth speakers!
Thank you for an excellent documentary, it was very interesting; thank you
Building my own bt speaker for bicycle with PLS-P830986 and SLS-85S25CP04-04, not tested in projected enclosure jet, but have feeling it will be great for outdoor riding.
@5:12 I would be suspicious that those elongated speakers are the woofers, with the "speakers" on the front being nothing more than port baffles to effectively increase bass response... will find out if I'm right after you get that bit apart. EDIT I was almost right, it was the other way around...!
Would have loved to hear the sound, see what it sounds like, since it's such an unusual speaker format.
How would it handle humidity? Does it sound like a bug zapper if used in the bathroom :-)
'Real' electrostatic speakers usually do just fine in any normal living room conditions.
In the bathroom, they will rapidly go to shit because the membrane is incredibly thin. Condensation will ruin it.
Interesting video ! You could convert this into a portable electrostatic headphone amplifier by adding a self bias stage on the output of the center tapped transformers, as is done with the STAX SRD-6 self biasing driver unit (see schematic). Add a couple of caps, resistors and diodes and voilà. Would be a fun experiment.
I'm a bit disappointed that they sent you the s model. It would have been nice to see inside the treVolo 2.
Check out Martin Logans. A dream when I heard them was the top of the line. One of the oldest was Janzen in the 60's had a h.v. tube in the power supply.
I'll turn a blind eye to the Rolf Harris moment you had @ 20:30 Dave ;)
I did enjoy this one. Those are some cool speakers. I learned something today about electrostatic speakers. Thanks Dave. Peace.
I'd like to see a flame loudspeaker. A friend of mine in the early 70's showed me one that he put together :)
You are confused... Philips (who used to make consumer electronics, you can still buy it but it is now just a label on equipment made by others) is not the same as Phillips of the screwdrivers and also not the same as the Phillips oil company.
Note the single L in Philips and the double-L in Phillips.
Electrostatic, well at least Martin logan, need to fire sound forward and backward. Also a lot of definitive speakers use passive bass radiators, seems to work well with a nice big surface area for the sound to move it, not sure if useful for that small.
minute 11:53there is alot of exiting happening cause you can see 2 ultra strong neodymium agnets of these little speakers. amazing
1:53 "None of that stereo rubbish."
Golden.
Are there any advantages to using these electrostatic speakers? Why not use a regular tweeter?
I don't own any, but... the theory is that having an entire vibrating surface changes the shape of the sound waves. The claim is they sound "larger" than a speaker box. You have to remember that some high end electrostatic speakers can be 5 feet tall (look up "Magnepan"). They've been around since the 60's. They can be very flat and compact. You could in theory hang them on a wall like a painting. Except they radiate backwards so it wouldn't sound very good. I think the biggest "advantage" for people is simply the novelty and cool factor.
Electrostatic speakers are way better for advertising .
A proper electrostatic mylar diaphragm has incredibly low mass compared to nearly all other speaker technologies. Driver mass, all other things being equal, is to speakers what mass is to cars. The lower the mass, the easier to accelerate.
Make them large enough and they can move a lot of air with no mechanical elements. You can actually make them a full range driver if the panel is big enough, but it's expensive and they get VERY large to do that, so usually they require a subwoofer. Martin Logan usually has a large (transparent!) panel above an integrated sub. I've heard them in person and the high frequency reproduction is incredibly lifelike.
Normally, electrostatics benefit from having extremely thin and light membranes. That means they can reproduce high frequency sounds more accurately since the membrane is easier to control than dynamic (voice coil) speaker. They don't typically vibrate at amplitudes as high as dynamic speakers, so they generally are not great at producing low frequency sounds. That's why they are often supplemented with dynamic woofers.
It makes naive people think they're getting something special? An electrostatic tweeter (well, "ribbon tweeter" of various descriptions) can be excellent for stereo imaging, which is giving the illusion of sound coming from somewhere inbetween the two speakers. I'm talking mid to high end studio monitors, not so much this particular speaker.
I remember year ago, probably late 70’s Wireless World magazine did a project over many months on a DIY electro static headphones, that one could make, I never tried to may it my self, it seemed a way to DIY ETC myself.
+Gary Miles YES! It was Wireless World 1973 and my roommate at uni built a pair. They worked stupendously well. They looked lashed up of course, but the sound quality was phenomenal. Easily better than some quite expensive Sennheisers we used at uni at the time.
The spatial field and high frequency response were truly amazing. I tried out some STAX electros of the day in a top audio store and I'd say the DIY ones sounded just as good ... I actually preferred the sound of the DIY ones.
Quad ESL 57's the Daddy of Electrostatics, full range too, not just electrostatic tweeter. Date from 1957, I had a pair for over 45 years.
Radfordperson Yes! My wife wouldn’t let me have them in the house - they looked like old fashioned electric convector heaters in a kind of off-gold colour. Needed to be rather large to get any sort of bass response.
+Radfordperson I'm just guessing from the name obviously but were/are you a Radford amp fan or even an ex employee? Be interested to know as I worked for Arthur in 1973/4 as a student engineer.
Hi Bob, you are correct, I have a very nice STA25 III, SC22 and FMT2. Amazing that you worked for Authur. I would be interested in any info available. I'm on pinkfishmedia as Radfordman. I used to know Jim Rogers.
Hi Richard, I don't blame your wife, they are a bit intrusive. In fact I have two pairs and have thought of double stacking them.
Yess! Ive wanted to see a teardown of one of these! Seems these use the same drivers as the Bose sound link mini?
Over my system (and your recording) the BenQ speakers sounded far better to me. None of the chestiness that you got from the Focals.
One other thing the extra grounds may be for is EMI control.
I am in 3:04 in the video.
I wonder what you will say what the point is in having such a small stereo base line.
But on with the video .....
You are measuring impedance and transformer ratio using your DC ohmmeter? That is interesting...
If those were conventional electrostatic speakers I'd hazard a guess you'd get a modest amount more power out of them.
Nice edit around the use of the word "funky"
I remember hearing a proper set of electrostatics a while back. Their were actually vintage floor speakers that used them as the tweeters, they sounded like modern speakers! It's too bad this is a poor example of them. Electrostatic speakers are still made for home audio.
I'd be very interested to know what rail voltage the amp is running on and how, if any, they step up the battery voltage
Dave, how does the engineers on those projects always come up with those highly specialized chips? Like this Bluetooth chip, I bet I can't find it on Digikey or Google it.
Are those engineers just highly specialized and keep up with what's going on with their applications, or are there companies specific for consulting on "where can I find the best chip for my project?"
The industrial designer looks to have cut their professional teeth on Sony equipment. Unfortunately the loudspeaker systems designer seems to have learned their trade at Amstrad in the late 1980s, and then had the last cent of cost beaten out of them in backstreet Shenzhen. Embedded electret sheet? That's incredibly low budget crap. I don't think Quad ESL have much to be afraid of.
Zadster, I believe you will have to translate this into more normal English for rational consumption. LOL
@@BruceNitroxpro 'It's very pretty and sturdy but full of hot air and bullshit' :D
That was absolutely splendid English. Moreover, the meaning was conveyed fully and succinctly.
Just in case you are too young, or not from the UK.
Amstrad were Alan Sugars attempt at building cheep as fuck electronics in the 1980s, packaged up in an effort to look half reasonable to anyone with little to no idea, or around 90% of the population. They were plastic silvery boxes, with basically fuck all in them but the most basic of components, usually the very minimum on one board, with the thinnest of wiring.
An insult to electronics and design, especially quality audio.
They were, in a word. SHITE!
So now that they're refurbed, how much do you want for them??
Great video, thank you!!
I never realized that you were size, until I saw you with that knife.
I’m wondering if a low powered Cr 3032 battery powered audio player could play a stereo waveform that simulate a 50hertz ac sine wave and then stepped up and rectified to a usable power source. 🤔😯
How do you keep your stuff clean and so dust free???
AKM 722 is a Hall effect current sensor I think.
The letter 'c' missing from 'expected' on-screen text at 28 minutes...
4 minutes of black screen at the end, followed by some text?
Interesting...but £150 though.....I'd play with one for half that....
I did used to own a pair of Quad Electrostatics back in the day....wish i still had them today...
Dave! Where is the Triplett 630-NA???? There was a sad lonely empty space on the shelf where it once was. It's two brothers even looked sad. The whole time I was watching that video, I just couldn't quit wondering. It's totally my favorite multimeter, or excuse me, Volt-Ohm-Meter. Well, it's soon to be second favorite! Because I just ordered my 121GW from your webstore!!! YAY!!!! I'm soooooo excited. I've been wanting one like totally forever man! As soon as I get it, I'm going to do a review on my joke of a youtube channel that has now reached 6 whole subscribers! Now, it's possible that one of those subscribers might be my mom, but hey!
Oh,, could you please sign my multimeter? It would be totally awesome!
It's ashamed it's an elecltret speaker because otherwise it looks like a very well designed and constructed speaker that I'd consider buying if the price was right. OK after clicking the link in the description and seeing that they cost $299 there is no way in hell. In the $300 - $400 range you can buy the KMC3, Klipsch Music Center 3, Portable Bluetooth 2.1 speaker that puts out quite substantial bass for a 5" ported woofer. Crystal clear never a hint of distortion even at full blast. Peak rms 135 watts. Discontinued but findable still.
Dave.. Did you put the meter onto the divider fabric to see if it's conductive and grounded to the metal frame?
The divider is not connected to anything. It would be pre-charged.
No offence but your voice cracks me up when you go high !
Nice little "bowie"👍!interesting cannel,rockn rolly!👍
This kind of speakers never had amazing sound but what you heart was the transformer! Ferit core it's not for audio. You will not believe the deference in quality if you put iron core!
I wonder if those electrostatic speaker elements would make a good mosquito repeller ?
Never seen a set of two Bluetooth speakers it's always been one unit would hinder the portability factor if there were two.
I always wanted to see in those electrostatic speakers.
cool...needed somethin decent to watch! thanks Dave
whats with the 3 mins of black silence followed by a few words at the end?
I goofed the render
"They've got this new bluetooth... consumer ... (wank sign).... thing, anyway", LOL at1:02
It demonstrates the main problem of electrostatic drivers: you get no bass. I have a pair of Hosiden DH-77 headphones, really flat, very 80s style, it has an excellent mid and high range and noooo bass. Must be an 80s thing, I bet they go amazing with synth music.
piezo electric i guess explains the transformer to step up and as well explain why there is no BIAS voltage. i do hope they DONT call it an esl since it is not !! distortion wise proable even worse then a common speaker
I'm horrified that you are poking it!
Damn you dust cap squashers! :)
Great teardown as always Dave!
Haha :D Dave starting to airwank just made me laugh way too much
HAHAHAHAHA I love the way you discover the weight of the thing AFTER you take of the wrapper! HAHAHAHAHA