Andy Powers Replies to my V-bracing Question

[archerscreek]

I’ve never been a fan of the Taylor sound. However, I am impressed that Powers took the time to write a lengthy response explaining guitar design and did so at a depth/level rarely seen from any industry reps or insiders. That was class.

[robj144]

This is more or less what I was speculating in the original multi-page thread on V-bracing:

"Well, I'm saying it could be actually be intonation in regards to how the notes coming out of the guitar are closer to the harmonic series produced by the strings. In other words, perhaps on a certain fret higher up on the fretboard, the string produces a fundamental frequency of 440 Hz (an A). But, after the note is coupled to the guitar, it might shift it to 440.5 Hz or something similar. I don't know if that's the case, but it could happen."

[Seagull S6]

Originally Posted by Erithon

Yes, the undertone series and subharmonics are real, but do they really apply to the acoustic guitar? (I have no idea - if someone knows, please jump in!) The very Wikipedia article you cite states that "The overtone series can be produced physically in two ways—either by overblowing a wind instrument, or by dividing a monochord string." The former is clearly irrelevant, and the latter seems to be too (unless someone has a guitar with a movable bridge). Now it may be that the information on Wikipedia is wrong or incomplete, and Andy certainly would be knowledgeable in this area so I'm willing to take his word (albeit with a grain of salt because: marketing); if Andy is correct, does anyone know how exactly the acoustic guitar produces undertones?

My gripe Is someone claiming they don't understand something so there for it isn't valid and If they feel like it they will prove that Andy is just blowing smoke.

Given that, IDK if any of the science referred to will make any difference in the finished product because when you try to apply science to something as subjective as tone the science doesn't mean much until you can observe the results.

[JohnW63]

I don't think that Andy's goal is to build a sterile guitar with very little overtones, but to build one with less opposing ones or off tone ones. The V bracing is an attempt to guide the overtones into ones that are more like the primary one.

What comes to my mind is a twelve string guitar. I think most people can't tell when their 6 string is a tiny bit out of tune, from one string to the next, but if you have one of the strings of a 12 string pair off, it really is obvious. The tones are no farther off than most people play their 6 string, but because the 12 string pairs are SO close, the tones seem to highlight their differences.

Perhaps Andy is trying to keep the top from resonating in harmonics that are a touch out of tune from the fundamental and related frequencies. Or, maybe I have missed his explanation by a wide margin.

Could it be that the X bracing was not designed for best possible sound, but easiest way to make the top strong enough for steel strings and still light enough to resonate loud enough ?

[Picker2]

Originally Posted by Monsoon1

Criticisms without input accomplish nothing.

Not entirely true. It makes people think. :-) But you do have a point of course, so please read below.

Originally Posted by Herb Hunter

I note that though you say, "a lot of what Andy writes does not make sense,” you only list one item. Given that statement, it seems to me that you are obliged to list more than but one nonsensical example.

I’m not willing to categorically state something doesn’t make sense merely because I’ve never heard the term before. The most I might say is it doesn’t make sense to me given my lack of familiarity.

I assume that by undertones, Andy is referring to a subharmonics.

Herb, please read below!

Originally Posted by Rudy4

When you start breaking down complex waveforms with techniques such as Fourier Analysis you begin to understand that each new harmonic of the primary tone has generated lower level frequencies that are sums and differences of each of the frequencies and harmonics

Can you please elaborate on what you mean exactly? What is a “new” harmonic? Why would such a harmonic generate lower level frequencies (which I assume are subharmonics)? (I’m an expert in laser physics, non-linear optics and magnetic resonance imaging. I grew up with Fourier Analysis and understand it in every little detail. As a physicist, I have a pretty good understanding of basically all technical aspects of the world around us, with specific interest in guitars. So don’t be shy!)

The only way I see subharmonics are generated by a guitar string is by the attack, not by the decay. The attack generates a wide frequency spectrum, which may excite resonant frequencies in the body that are dissonant with the harmonics of the decaying string. This is, however, no big deal. The dissonant
attack lasts only a short while and has a very low Q (= a wide peak in the frequency curve, which corresponds to a ‘hissing’ sound). It’s like the ‘thud’ sound when you tap the bridge. You don’t perceive it as an harmonic distortion or ‘out-of-tune-ness’.

With bowed instruments it’s a different story, because the bowed string feeds white noise into the body continuously, which may excite a dissonant body harmonic at high volume. These are the infamous wolf tones. But this does not happen on plucked string instruments.

The way I see it, the best way to construct a guitar is to prevent or reduce resonant peaks in the frequency response curve. Just like room acoustics in a recording studio. But that’s another story.

[M Hayden]

I wonder whether the change is intended to get the top moving in a consonant way across a wider range of frequencies? The V-braced guitars do have a remarkably smooth sound with very little of the warm growl (my term, just the sound of the strings interacting) found in ‘normal’ steel strings.

[gitarro]

I once played a guitar (not a taylor) that sounded to my ear as being totally in synch with itself. Every string when strummed seemed to resonate exactly in line with each other and faded to silence at exactly the same rate. There was not a single overtone out - every part of the note seems to resonate in synch on every string. It was like playing a synthesizer except it was acoustic.

It was pretty nifty to play it and experience it for a few minutes but beyond that, the tone and even the resonance became so uniform that it was boring. You could say it was perfectly balanced in every way but if it is too coherent and in phase, it can end up sounding lacking in colour.

Therefore i wonder if it may not be wholly desirable to have a top that vibrates too uniformly. Could it be that the chaos who is seen as the enemy by the v class bracing school is the very thing that helps make the tone interesting?

[Picker2]

Originally Posted by M Hayden

I wonder whether the change is intended to get the top moving in a consonant way across a wider range of frequencies? The V-braced guitars do have a remarkably smooth sound with very little of the warm growl (my term, just the sound of the strings interacting) found in ‘normal’ steel strings.

Different bracing means different settings of your “multi-band equalizer” means different tone. You may call that “growl” or “smooth”, that makes perfect sense. But it has nothing to do with intonation. It only has to do with tone.

[Picker2]

Originally Posted by gitarro

I once played a guitar (not a taylor) that sounded to my ear as being totally in synch with itself. Every string when strummed seemed to resonate exactly in line with each other and faded to silence at exactly the same rate. There was not a single overtone out - every part of the note seems to resonate in synch on every string. It was like playing a synthesizer except it was acoustic.

Was that by any chance an Adamas’s SMT? The most perfect guitar ever produced? And indeed so perfect and predictable that it gets boring. :-)

[gitarro]

Originally Posted by Picker2

Was that by any chance an Adamas’s SMT? The most perfect guitar ever produced? And indeed so perfect and predictable that it gets boring. :-)

No it was a lot more custom and expensive than an adamas...

[Picker2]

Originally Posted by gitarro

No it was a lot more custom and expensive than an adamas...

Good job :-).

[gitarro]

Originally Posted by Picker2

Good job :-).

I expected much better though from that guitsr and it was disappointing to me in the end.

[Erithon]

Originally Posted by Seagull S6

My gripe Is someone claiming they don't understand something so there for it isn't valid and If they feel like it they will prove that Andy is just blowing smoke.

I totally agree. (Sorry if that wasn't clear!) My intention was not to counter your reply, but to nuance it by pointing out that while someone not understanding or ever having heard of subharmonics isn't a reason to dismiss Andy's reply, it still remains to be demonstrated (at least to me) that the guitar generates subharmonics in the manner indicated by his reply.

[Picker2]

Originally Posted by Seagull S6

Just because you haven't heard about something does not mean it doesn't exist.
https://en.wikipedia.org/wiki/Undertone_series

That is true. But as a physicist with specific interest in acoustic guitars it is at least likely I would have heard about it. I know what subharmonics are. I also know they are irrelevant for the intonation of an acoustic guitar, as I explained in more detail in another post in this thread.

[Bill Yellow]

Undertones in a resonating body are real. The church bell is the textbook example, where we hear a low drone somewhere near a major 6th below the Bell's fundamental resonant frequency.
My guess would be that for a vibrating piece of wood, the subharmonic content is minimal but contributes to the overall tone along with the imperceptible high-order overtones .