Andy Powers Replies to my V-bracing Question

[rogthefrog]

Originally Posted by Picker2

OK. Fair enough. Although I actually meant a bass drum stuffed with a blanket (very low Q). But if anyone believes a bass drum stuffed with a blanket always interferes with a piano to such an extent that the piano seems to be out of tune, well, then I understand what Andy says.

However, that brings us immediately to the next (and probably more important) question: you can tune a drumhead by turning a bunch of screws. But how does V-bracing tune the guitar top? This was never explained by Taylor. It was only stated that the top moves more orderly, that the vibrations are more limited to sideways motion etc. But how does this tune the guitar top, systematically and principally, for every single V-braced factory-built guitar? Now THAT’s what I would like to understand.


Grafted walnut. American Walnut trunk with a European Walnut branch grafted into it. Wait a 100 years and the branch is big enough to build a guitar from. Cool huh? But don’t order such a guitar when you’re in a hurry .

Ok I think we're on the same page--i don't completely understand the physics of the v bracing and they haven't been explained entirely convincingly.

Fabulous walnut.

[Denny B]

I think I'd like to test drive a V brace first chance I get...

If I like it, I might be interested in picking one up...

If I don't like it, I'll just continue to happily play the Taylor I have...

[Charmed Life Picks]

To the OP: thanks for posting this.

I am not a Taylor player, but so many millions are.

As a seller of things, and having a background of selling high end brands as a field rep for Alpine, Nakamichi, Carvin, TDK, etc., my perspective is what Taylor did (or didn't) do to help their dealers. If this new line came in as a complete surprise and the new thing is what they're pushing, you have many dealers who are left with $100,000s or even millions of dollars in old, dead inventory.

Does anyone know if Taylor prepared or compensated their dealers for this? These kind of vendors do NOT take back old inventory already in the dealer's warehouse, unless the dealer is about to go out of business and needs some relief.

This may have been addressed earlier in this thread, but I'm just too slammed to read it.

thanks,
scott memmer

[Picker2]

Originally Posted by printer2

Section 1.4.4 goes through the issue of coupled resonators and their moving the resonant frequency. It is one of the more valuable pieces of the guitar making puzzle in the books (set of two) and help to justify the $300 cost to me. The authors go though the mathematical theory why the resonators behave as they do and offset the string's frequency creating an out of tune note. The book goes on, I did a quick search on the net to see if I could find something to point to rather than me retyping the mentioned chapter. Lot of straw making finding the needle tedious. That is about as much time as I have this morning, got to go.

Looks like a great pair of books. Too bad they are hard to find. If they wouldn't cost 300 bucks I would buy them unseen. Bit for that price I'd like to browse the books first. Maybe you can send me a picture of section 1.4.4 by PM so I can have a look?

[HHP]

Originally Posted by Charmed Life Picks

To the OP: thanks for posting this.

I am not a Taylor player, but so many millions are.

As a seller of things, and having a background of selling high end brands as a field rep for Alpine, Nakamichi, Carvin, TDK, etc., my perspective is what Taylor did (or didn't) do to help their dealers. If this new line came in as a complete surprise and the new thing is what they're pushing, you have many dealers who are left with $100,000s or even millions of dollars in old, dead inventory.

Does anyone know if Taylor prepared or compensated their dealers for this? These kind of vendors do NOT take back old inventory already in the dealer's warehouse, unless the dealer is about to go out of business and needs some relief.

This may have been addressed earlier in this thread, but I'm just too slammed to read it.

thanks,
scott memmer

If I understand their plans, the new bracing will be limited to a couple of higher end models initially so the bread and butter revenue items will remain as is for some period of time.

[Herb Hunter]

Originally Posted by KevWind

Would you mind telling me the name of iPhone App are you using to generate this graph ?

I have a suite of apps on my iPhone called AudioTools by Studio Six Digital. It contains sound level meters, a real time analyzer, Fast Fourier Transform, Dual Trace Audio Oscilloscope and Signal Generator among several other apps.

https://itunes.apple.com/us/app/audi...325307477?mt=8

[Inyo]

Originally Posted by Charmed Life Picks

If this new line came in as a complete surprise and the new thing is what they're pushing, you have many dealers who are left with $100,000s or even millions of dollars in old, dead inventory.

Does anyone know if Taylor prepared or compensated their dealers for this?

Originally Posted by HHP

If I understand their plans, the new bracing will be limited to a couple of higher end models initially so the bread and butter revenue items will remain as is for some period of time.

The revolutionary V-brace is available on 4 Taylor cutaway models, only--that's all.

And, indeed, the V-brace does improve intonation on a cutaway.

Just run a strobe tuner test on one. Notes on the V-brace cutaway don't oscillate much at all (they remain "rock solid," in the words of independent investigator Guitar Magazine), different from the way notes plucked on a traditional X-brace cutaway wander unsteadily.

Which means that--unlike strings picked on an X-brace cutaway--V-brace cutaway notes don't continuously waver a few cents between flat and sharp. Intonation is thus markedly improved on a cutaway with the V-brace system.

[TD2]

I hope Taylor is paying attention to this thread and hires all those that know so much more about guitar design than their lead designer.

[printer2]

Originally Posted by Picker2

Looks like a great pair of books. Too bad they are hard to find. If they wouldn't cost 300 bucks I would buy them unseen. Bit for that price I'd like to browse the books first. Maybe you can send me a picture of section 1.4.4 by PM so I can have a look?

The section is six pages long and is only really a first step for the following sections. I wasn't going to dive into it in the near future but if I get some time I'll try to give a Coles Notes (Do you guys have that, maybe Readers Digest.) summery. I did have a problem with the cost but it is no different than any limited publication text book. It is well worth the money if one were serious about getting into building acoustic guitars.

[mattcran]

Here's a bump just for good measure.

[Trevor Gore]

Originally Posted by Picker2

Looks like a great pair of books. Too bad they are hard to find. If they wouldn't cost 300 bucks I would buy them unseen. Bit for that price I'd like to browse the books first. Maybe you can send me a picture of section 1.4.4 by PM so I can have a look?

Originally Posted by Printer2

The section is six pages long and is only really a first step for the following sections. I wasn't going to dive into it in the near future but if I get some time I'll try to give a Coles Notes (Do you guys have that, maybe Readers Digest.) summery. I did have a problem with the cost but it is no different than any limited publication text book. It is well worth the money if one were serious about getting into building acoustic guitars.

Interesting thread, with a lot of diverse ideas, so they can't all be right!

I was wondering how soon someone would mention "the book", which does explain what is going on using conventional scientific language and all the physics and maths to back it up.

The subject matter is coupled resonators and how two (for example) coupled resonators interact with each other. There are plenty of examples of how coupled resonators work, with particular special cases being harmonic absorbers (as found in cars) and seismic dampers (as found in tall buildings in earthquake zones). The book goes into detail about the importance of coupled resonators in guitars. After all, coupled resonators are all pervasive in guitars. That's how they work. The top couples with the air in the box which couples with the back etc. etc. as most people will be aware. But the string, of course, is a resonator which obviously couples strongly with the sound board, another resonator. When two resonators have similar natural frequencies and couple strongly, they will interact with each other. It doesn't really matter what physical form the resonators take (they can be electrical RLC circuits, for example), the physics and the mathematics are much the same, be there coupling between top and air or string and top.

One of the consequences of the mathematics of the situation is that the two coupled resonances "repel" each other. The resonance that was slightly higher in frequency in the uncoupled state gets pushed slightly higher, whilst the resonance that was slightly lower gets pushed lower in frequency. This can be demonstrated quite simply, using some of the tap techniques already discussed in this thread. Tap a guitar and you will typically see main resonances at ~ 100Hz (main air resonance) and at ~200Hz (main top resonance). If the sound hole is blocked the mechanism of the main air resonance is defeated, there is no coupling and so there is no longer a repulsion effect. Tap the body again with the sound hole blocked and you will find that the main air resonance has disappeared and the main top resonance has reduced in frequency, because the main air resonance is no longer repelling it upwards. The coupling effect between string and soundboard works similarly and has serious consequences for very responsive guitars, because if a body resonance on a responsive guitar is at, say, 184Hz (a typical region for a top resonant frequency) which is very close to F# at 185Hz, then when an F# is played the string frequency will be repelled higher and so play sharp, and the body resonance will be reduced in frequency. Because the string drives the soundboard, you hear the string frequency, whatever that is. The amount of sharpening can be up to 30 cents, which is audibly out of tune. This out-of-tuneness happens only locally around that note, so the open string (say the 4th string) will play true and the 12th fret may play true but the 4th fret will be out. Depending on the exact frequency relationship of the string vs. the body resonance, the played note can oscillate and I've no doubt some of you will have seen electronic tuners oscillate on some notes. So this oscillation may be what Andy Powers is referring to rather colourfully as "chaotic" oscillations.

There are basically two ways of fixing these intonation problems caused by over-coupling. The first is to do what most factories do which is to decrease the level of coupling between the string and the top by making the guitar less responsive, which is essentially just "overbuilding" it. So the problem is avoided. This is the "standard" factory solution.

However, that is not good enough if you want a responsive guitar that plays in tune. The way to fix it on a responsive guitar is to tune the body resonances as far from scale tones as possible, i.e. make the resonant frequencies of the body at a frequency exactly half way between two semi-tones. This is one of the things that modal tuning is about. You don't totally eliminate the out-of-tuneness, but you can make it a lot more tolerable.

So bracing can effect intonation, either by making the bracing stiff enough that you avoid the problem (the usual factory method) or by modally tuning the top by brace shaving to pitch it (and other resonances) accurately. I don't for a minute think that Taylor are doing the latter, but it makes a for a good story if you tell it in an obscure enough way that nobody can figure out what it actually means and they can define what they say as they like.

Full details and all the maths to back it up are in the book. Put my name and "book" into a search engine and it won't be hard to find. Most college level books on theory of vibrations will cover coupled resonators as does Fletcher and Rossing's "Physics of Musical Instruments".

One thing is true though. Guitars that are well intonated and play equal temperament accurately sound a whole lot better, but not many guitars are that well intonated.

[Goodallboy]

Originally Posted by TD2

I hope Taylor is paying attention to this thread and hires all those that know so much more about guitar design than their lead designer.

Pretty observant.......Self awareness is in short supply it seems.

[gitarro]

Originally Posted by TD2

I hope Taylor is paying attention to this thread and hires all those that know so much more about guitar design than their lead designer.

Wow...so according to you, only lead designers of major guitar manufacturers are qualified to have any opinion whatsoever on any aspect of guitar design, and the rest of the world is just too uneducated to do anything else but open their wallets and buy the latest product from them???!

Imho there are valid things that can be contributed by the manufacturer and by guitar enthusiasts and both can learn frlm.each other and the truth claims of both have got to be subjected to the same vigorous level of scrutiny. You don't get a free pass just because you are the lead designer of Taylor guitars.

[rogthefrog]

Originally Posted by Trevor Gore

Interesting thread

You just made it 10^3 times more interesting. Thanks for the lucid explanation.

Time for me to order The Book.

Thanks Trevor!

[Picker2]

Originally Posted by Trevor Gore

Interesting thread

Thanks for a great post, Trevor. If only Andy would have told the story like you do. Essentially you’re saying that there’s a penalty for trying to build a good guitar: it’s a non-linear effort. The more responsive you make it, the harder it gets. I would expect by the way that the issue is more dominant in nylon string guitars, right? And only for a handful of notes at most?

So it seems like if V-bracing would really systematically improve intonation, it’s basically because Taylor “overbuilds” the top.

It also seems you convinced me to buy the set of books.