Science of Sound: Guitar Physics
HTML-код
- Опубликовано: 11 сен 2022
- Why does an electric guitar or bass look the way it does? This video addresses the questions of string gauge, fret placement, and pickup placement.
References: Science, Waves & Sound Lecture Notes, section 7.
My free texts and lab manuals are available for download at my college web site www.mvcc.edu/jfiore and at my personal site www.dissidents.com
Inexpensive print and kindle copies are available at Amazon www.amazon.com/author/jimfiore
If you like my texts and videos, and would like to help defray the costs of making and maintaining them, consider making a modest donation at www.buymeacoffee.com/Professo... 
Наука
you make these topics so clear! thank you
thank you! the pickup position bit was was very good think. curious how it relates to range of motion over various string gauges. again, thank you. youve helped spin some gears in ye ole gray matter...
Excellent explanation
excellent teach. needs some physic knowledge to catch up, but ti can explain a lot of things about guitar
Sorry, but I'm still waiting for part 2 regarding pickups, which would have pratical use, because many questions were left unansered as far as I can tell...:
How thinner or thicker coil wire...vs more or less "turns"...affects affects both tone & output power. It appears that more "turns" on the pickup coil increases current & woltage out, while thinner wire decreases it...but with a net gain of current & voltage from more turns of thinner wire, but an increase of the frequency of the resonant peak.
I also understand that inserting a capacitor between signal & ground on the tone "pot" can increase or decreae (higher value "cap") the resonant peal of the overall output, while the latter increases the bandwidh of the higher frequencies the cap passes. Why & how is that? And how does the "taper" of potentiometers physically accomplished and what does each taper doe to frequency response as the "pot" is turned. And, I've a'ways thought that a tone control increased or decreased bass vs treble frequencies...but now I've read that it actually just decreased the resonant peak/ Is that right???
In fact, how do "pots", which are variable resistors, vs capacitors, in pickup circuits affect tonal & power output. And, is there any way to create, effectively, a variable capacitor using electronis as opposed to the tradional "tuner" device consisting of interposed metal plates?
And, how is frequency response & power output of a pickup varied based on whether one pickup is "on" vs 2 or more, and how is that output changed based on whether the pickups are in phase, or not, in parallel or in a series? I "get" that hum-cancelling is accompleshed by combining twosinglecoils with opposite winding direction & opposite polarity, as long as the magnet strength, number of winds & resistivity of the coil wire of the two coils is identical. But, how does that work?
There are "treble bleed" circuits ranging from a single capacitor, capacitor AND resistor (in a series, parallel, or 2 resistors...1 in a series & 1 in parallel with the cap)...But, how do these respective "circuits" affect level of treble tone as the volume pot is turned down...and why??? I understand that a variable resistor in a treble bleed allows the amount of "bleed" or treble pass-thru to be varied...but is the variable resistor to be in a series or in parallel with the "cap"?
I appreciate your videos...but sometimes they stress the theoretical, rather than the practical nature of this physics. And, while you talked about pickups for guitars...you can see that there are dozens of things you omitted! I thought you were going to create a Part 2 about pickups (which would cover the above)...but all I can find is about a minute about pickup harmonics, suggesting why some guitars have multiple pickups, in your Science of Guitars video. And, in that minute or so, you didn't even mention why the position of the pickups affects its tonal (as opposed to power) output.
I sure would like to see that Part 2 about pickups, that would explain even a fraction of the above...and how that knowledge can be put to use from a practical standpoint. THX
Well, you certainly have raised a number of questions, and as I always told my students, "Every good question deserves a good answer, and every good answer will lead to another good question". Everything you're asking would require several videos to address, but I'll try to hit a couple of them here and now.
First, yes, I do tend toward the theoretical, but that's because I'm an engineering professor and my target (students) want and deserve that sort of subject treatment. Granted, on YT, I recognize that there are a bunch of non-engineering students who watch these videos so I do try to slant a few of them in that direction. Can't please everybody, though. Anyway...
More turns generally leads to a higher output. The gauge of the wire is a practical limiter here (who wants a pickup that's 6" across?). All things being equal, a lower gauge number (i.e., thicker wire) will lead to less resistance. This resistance will interact with the coil inductance and any associated cable or winding capacitance to change how narrow the resonance is in the frequency range (i.e., the bandwidth or Q). A proper explanation for this requires a study of series and parallel AC resonant RLC circuits, and that's not trivial (I've got an entire playlist on the study of AC circuit analysis and one entire chapter of my free AC circuit analysis text devoted just to resonant circuits). In general, the smaller the capacitance and inductance values, the higher the resonant frequency, and the smaller the internal resistance of the coil, the sharper or more pronounced the resonant effect (ditto for a larger parallel resistance- indeed, a small series coil resistance can be shown to be equivalent to a large parallel resistance via a series-parallel transform).
The taper of a pot doesn't change the frequency response, per se. Taper simply refers to how the resistance change is distributed across the range of motion. A linear (standard) taper will be 50/50 resistance when the pot is centered. A log or audio taper pot will be 10/90 when the pot is centered. Typical volume controls use an audio taper. If you used a linear taper, then if "10" is fully clockwise and "0" is fully counterclockwise, "noon" would be about "9" instead of "5". IOW, there would be very little volume change over the last half of the rotation. It would still work as a volume control, it's just that it would be very sloppy on one end and very touchy on the other end.
As far as variable caps are concerned, electronic versions of a variable capacitor are available but they're probably not what you're looking for. This is normally achieved through something called a varactor diode. A reverse DC bias voltage sets up the capacitance. It is quite small though (think in terms of picofarads). It is fine for electronic tuning of radios but not very practical for something like a guitar (for a variety of reasons).
I do address the tone changes caused by pickup position toward the end of the video above. Usually, when people refer to "tone" they're referring to "tonal balance" or how the high frequency levels compare to the lower (or middle) frequency levels. As any given note is made up of a fundamental plus a series of higher harmonics, then any change in those levels (i.e., some frequencies being boosted or reduced compared to others) will affect the timbre (i.e., the tone). The pickup position does exactly that- as you move the pickup closer to the bridge, the lower frequency levels tend to reduce compared to the harmonics. The end result is a sound that people will describe as thinner, bitey, brighter, or less mellow. These are tough terms though. It is hard to use words to portray with accuracy something that you hear, unless we all have an agreed upon vocabulary for that. I mean, I can say that technically speaking, the fundamental's amplitude is lowered, but how does that translate into what you experience as a listener? How do you describe "blue" to someone who has never seen the color blue? You can't say "It's kind of like green", right? Reminds me of how people say lobster tastes like chicken. No. If you've had both, you know that lobster doesn't taste like chicken. It tastes like lobster. Maybe it tastes closer to chicken than it does to, say, bacon, but that doesn't mean they taste the same. Fun stuff to think about.
Not sure what your background is, but here are a couple of videos from my semiconductor devices playlist that discuss the interaction between an amplifier, guitar pickup, and the cable between them:
ruclips.net/video/f7dtLt5igeE/видео.htmlfeature=shared
ruclips.net/video/UeCEdn516ZY/видео.htmlfeature=shared
PS - You win the prize for the longest comment reply I have ever created on YT. ;-)
Nice explanations, do I wish you got a bit grittier into the math, trying to learn about intonation changes and compensation for temperance like stretch tuning. also I have a nylon string and only the largest 3 strings are wound, sometimes like 19 cents off as a difference from the 4th to octaves, and would like to see how different strings might help normalize the tension disparity.
All interesting bits to be sure, but a little more than I can cover in an introductory video. 19 cents is quite a bit. Has the instrument been set up properly (using that set of strings)? For ideal strings, the diameter* does not matter but there is a small correction factor for real-world strings based on diameter (same thing is true for resonant pipes in case you also play a wind instrument). In practical terms, though, the important thing is making sure that the guitar has been set up by a qualified luthier. No note should be off by 19 cents on a correctly tuned instrument.
*to be clear, that statement assumes the two strings have the same mass per unit length (which implies that if they have different diameters, then they must have different densities, i.e. made out of different materials or using different construction).
can I understand like this: (1) on the same fret, diameter of string is determied by the cycle of fifths; (2) On the same string, the fret distance is determined by the half note frequency ratio?
Yes, if by "half note" you mean "half step" or semi-tone.
what does the shirt mean. I must know
It's based on languages and communicating ideas. One part is musical notation, the other comes from the C programming language. Thus, it's a combination of art and technology. If you know C, it might make sense to you.
@@ElectronicswithProfessorFiore a pointer to a half note with post fix increment is what I read initially, but I thought it might be a joke I didn't understand.
@@eli-nm1ng OK, so in the context of music notation, what might that mean? (BTW, it's an eighth note but that's not really important)
@@ElectronicswithProfessorFiore chromatic scale?
@@eli-nm1ng That's not the way I interpret it, but whatever works for you is fine with me.
23:00
The analysis is inaccurate and the terms are wrong. The neck pickup would sound fuller and warmer and the bridge pickup would sound more biting and brighter, and the most important thing is that the areas of vibration change depends which note you press. So the pickup would get different vibration areas. Playing on the same string on the first fret and on the 17 fret will have different results because at the first fret the string already vibrating in the area of the second fret and on. That's a long way from the pickup itself.
There's also the fingers position of the plucking hand that affects the sound much more then any other part in the sound.
Why? Because while the rest of the sound ingredients are fixed more or less. The hand moves freely and the area of plucking will affect everything regardless which pickup works.
Try it out with different pickup combination and plucking. Than, explain that physics.
There may be some confusion on terms as I am thinking that we don't fundamentally disagree. As I said, the bridge pickup would have stronger high frequency overtones relative to the fundamental than the saddle pickup would. How do you want to describe that in aesthetic terms? If you think in terms of boosted highs, you might say "bitey", but if you think in terms of less lows, you might say "thinner". I've been playing bass about as long as I've been a professor of electrical engineering and technology, so I appreciate the issues of terminology between the engineering/science and artistic worlds.
It is true that where the nodes and anti-nodes show up on the string is a function of where you're fretting, but I'm just looking at a single variable here to help clarify a complex situation. Otherwise, you have so many variables that it is hard to see the contributions of each part. And sure, where and how you pluck (fingers, thumb strike, pop, pick, etc.) play into this, but again, it's best to explain the effect of each part. In this case, that's the general effect of the location of the pickup on the timbre produced.