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call if sending it up the flag pole and see if we salute it.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Where's the data?

Andy

I was thinking you get this same sort of nonsense every year with new golf clubs yet I can't hit a ball any further or straighter with my new clubs than I could with my old clubs. Taylor guitars, Taylormade golf clubs - coincidence? I don't think so.
Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Well, John has it pretty right. I deal with coupled resonators in Section 2.2 and the effect of this coupling on intonation in Section 4.7.2.

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, the physics and the mathematics is 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 resonances "repel" each other. The resonance that was slightly higher in frequency in the uncoupled state gets pushed slightly higher, whilst the the resonance that was slightly lower gets pushed lower in frequency. This 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. 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 (likely when tuning an open G 3rd string for example). So this oscillation may be what Andy Powers is referring to rather colorfully 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.

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.


Hmmm. Sounds familiar. Try Section 4.5.1 for a more cogent explanation.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

A reference your falcate "epiphany"?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I have seen, and others already mentioned that these oscillations or overtones occur quite regularly on solid body electric guitars all the time as well. And as you allude the G string is often the worst offender on these instruments too. So am I to infer that the body, in this case a solid slab of hardwood of random species, size, mass, etc. is producing this effect in this case? Even though the output I am using to sense the note is completely electro-mechanical (Faraday principal) and as such any vibrations of the "Top" or entire body are almost entirely removed from the actual signal path.

I must also point out that when we put an acoustic guitar on the strobe we are often using a sensor clip on the headstock and thereby adding in sympathetic vibrations from beyond the nut or fretted note that are not part of the tone that is amplified by the top/body. And adding them very strongly as they are closer to the sensor than the amplified note.... which skews the purity of the pattern versus the note as heard. And except for cheap UST's most good quality acoustic pickups have multiple sensors, mikes, etc picking up from different components of the sound production chain all having different latency to the source (vibrating string) and again causing a hazy picture on the strobe. Cheap UST units add enough quack and other color to a note That i would not trust one as an accurate sonic picture of tone of the guitar on a strobe or even a spectrum analysis.

And isn't a spectrum analysis the only way to actually pinpoint and spot the transient unwanted tones that you mentioned? Wolf notes....





Absolutely no argument. And there are many approaches to get that done. Took an in depth class with some techs from Earvanna many moons ago and have seen that more improvements will come from adjusting the nut but it never caught on.... And actually I found my customers did not like the sterile sound of the Earvanna on acoustics. That softly sharp out of color of the first positions is what some people expect an acoustic to sound like.....Just like if you were to remove the frail from the banjo....the world may thank you but players wont touch it.

But my point there is that the Earvanna nut makes a difference that can be strobed and proven effective and it's method is adjusting the strings entire position relative to the frets and the other strings......adjusting string length = better intonation.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Man this has got me reading things like when I was new to this..... Got to thinking how archtops seemed to change from a straight bracing similar to this V class to X braced in about the 40's.....

Found this,

Archtop Guitar Bracing Benedetto Notes
Acoustic Archtop Guitar Bracing – Bob Benedetto

Acoustic Archtop Guitar Bracing
by Bob Benedetto

".........Archtop Guitar Bracing Patterns

Archtop Guitar Parallel Bracing. Most makers and players would agree that, in general, there are two preferred bracing patterns: Parallel bracing, which results in a louder, more punchy voiced guitar, and X bracing, which may best be described as being warmer and with more balance between highs and lows. The latter usually (but not always) is better suited for the modern player.........."

Read the full text here: https://theartoflutherie.com/acoustic-archtop-guitar-bracing-bob-benedetto/

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Brian - that is a very insightful and salient point! Thank you for pointing that out.

Also, thank you for the archtop references. That brings another viewpoint to the discussion that is meaningful in light of Taylor's new marketing BS. I'm not knocking innovation in guitar building theory, but we CANNOT discard what we know to be true from decades of experience.

We work in a world of imperfection while trying to attain the unattainable. I suppose I could be nice and saw that Taylor is exploring ways to do that, but I think their recent claims fall short of the goal.

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"Act your age, not your shoe size" - Prince

Very interesting thread. As in all things the proof of the pudding will be in the tasting. All of the videos I've seen on this have hardly any playing but plenty of talking. Can't wait for the comparison videos to begin.

My guess is in certain keys, played in a particular position, this bracing will work as stated. But who wants those limits on their playing? It will be interesting to see how it shakes out. I'm hoping Taylor has come across a true inovation.

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Joe Beaver
Maker of Sawdust

No, that's another story altogether! In that section I was explaining how standing waves in plates form (by an incident wave reacting with a reflected wave) which is a criteria for any standing wave to form and gives rise to what we often refer to as modes of vibration.


There are a number of reasons why electronic tuners can give an oscillating reading. For solid body guitars it could be the body or the neck causing it, but either of these is less likely than the tuner itself switching between two different partials when it triggers.

The way most tuners work is to trigger on the highest amplitude partial. If the partials are harmonic (integer multiples of each other) it doesn't matter which harmonic is being used as a trigger. All will deliver the same result. But partials are seldom exactly harmonic for a variety of different reasons. For a solid body guitar, plucked at ~ quarter string length from the bridge (a normal plucking position and also pretty close to a pickup) the second partial is often of larger magnitude than the fundamental. So triggering takes place on the second partial. However, often the second partial decays faster than the first, so at some point the triggering switches to the fundamental, because that is now the highest amplitude partial. This is no big deal if the partials are harmonic. But a G string, for example, unwound on an electric, and one of the stiffest (in bending) strings on the guitar, is the least likely to have harmonic partials. All the higher partials get progressively sharper. And as the triggering switches between partials the tuner will jump. Plucking over the 12th fret (open string) makes it pretty certain that the highest amplitude partial is the fundamental, so you will see a lot less of this phenomenon.

Another reason is the rotating plane of transverse oscillation of the string. Typically the plane of oscillation moves around between perpendicular to the face of the guitar to parallel to the face of the guitar. The frequency of vibration only remains the same if the impedance at the string terminations is the same in all planes, which is seldom the case, so its frequency changes slightly as the plane of vibration rotates.

On classical guitars, both the main air resonance and the main top resonance are often close to G, so as well as the above, you see the body coupling issues as well.

If you download a (free) tuner called AP Tuner and select View/Harmonic graph, you can see how all the partials move in frequency relative to each other and you will be able to see these things for yourself.


The Earvana product no doubt helps, but is a bit of a "one size fits all" solution. Of course, one size does not fit all because people use different strings and setups, which changes the solution. But custom solutions aren't that hard to do. All explained in the book.



If a customer prefers a less accurately intonated guitar (and some do) that's not hard to achieve either!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

A good discussion. One of the things Trevor pointed out I think is a useful thing to be aware of:

"Plucking over the 12th fret (open string) makes it pretty certain that the highest amplitude partial is the fundamental, so you will see a lot less of this phenomenon."

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Steve Smith
"Music is what feelings sound like"

Trevor,
I thank you for your time in this as I am finding this topic quite fascinating. So lets look at the G string issues in particular as they are the easiest to see on all type of guitars and tuners. I have always attributed the G string partial phenomena to a phase type action caused by vibrational length versus pitch causing a phase reaction of similar type to what we account for when designing a live room for show or recording where any frequency suffers phase cancellation at 25% the wavelengths distance from a wall or other reflective surface. This same wave phasing of the original source in a room us also the sound you recognize as reverb when the waves slide over eachother from different directions. And I readily concede that the air box of an acoustic guitar is a room, a reverb chamber, albeit a small one.

The math doesn't hold out the same but that does not mean that it is not an odd phase issue. In fact the numbers for the G string fall close to 33% wavelength....Close....22.78" would be the actual one third of a G3's wavelength. Just shy of most modern guitar scales.

But any theory of mechanics that does not completely account for the same reactions in solid electric instruments must be flawed, somehow.....Occam's razor would dictate that two such similar systems experiencing the same phenomena would have the same root cause.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I agree but if one is considering phase reaction of the room (guitar box) don't forget the same type of reaction caused by the sound hole (similar effect to a bass reflex speaker's ducted port). While small, it could be a factor.

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"I've been had again"
Tim Benware
Creedmoor, NC

I am not too quick to discount Taylor's new bracing. What if their new top spreads out the main resonances so they are not as peaky, a lower Q for people that know the term. What if the top behaves more like a lattice guitar with the diaphragm with a looser surround? They do have their new bracing but still do the channel rout around the soundboard. Say they stiffen up the soundboard and loosen up the suround to get back some bass. Get rid of some of the higher harmonics should also help out with the 'intuneness'. They are treating the top as a classical top with a lower transverse brace. Maybe this with the routed channel and the brace pattern gives more of a speaker cone effect. As we all know the sound is the sum of all the design aspects and it may not be kust because the two main braces are in a V shape.

I posted pictures of Pepe Romero's uke where he uses reversed fan bracing.

https://i.imgur.com/MzO93Ni.jpg

He uses the same idea on his guitars after he played an instrument by Miguel Rodriguez that had reverse fan bracing and it seemed to have a great impact on him.

https://www.youtube.com/watch?v=w00ty90qZcI

So is it that when the top breaks up into smaller nodes to produce the highs that they are coming of the top from the sound hole part of the top where they were coming from the bottom with the X brace? Is the bracing by the sound hole keeping the area vibrating in a lower number of nodes that higher nodes? Maybe it is something altogether different. Sure Taylor is doing the hype thing to get sales but maybe they and Pepe Romero have something.

The language Taylor uses may be wrong or exaggerated but there could be an element of truth to it. I thought, ok, look for a steel string guitar braced with fans like a classical I could not find one. Maybe an inverted V-Class guitar sounds just as 'good' as a V-Class guitar? But then Taylor could not really patent (they did the V-Class bracing) a fan braced guitar. Until somebody copies their bracing, trys the guitar then strips off the bracing and puts an X brace on it and compare the two we will only be armchair quarterbacks. At the moment we have nothing to go by to say their system doesn't work better.


Please don't throw too many sticks at me.

interesting discussion. has Taylor any comment on how they have improved the mechanical rigidity of the neck block? in terms of arresting flexure of the instrument while being played and it's effect on scale length? they may have solved the questions of "note purity" and i'll need to hear this for myself, but reducing the instruments tendency to buckle and oscillate axially while playing can do much for intonation regardless to what's been done with the plates. in this area Taylor seems to be for now just following the usual methods.

"I thought, ok, look for a steel string guitar braced with fans like a classical I could not find one."

I am bracing my soundboards with fan braces and an X brace. Some of the fans pass under the X and into the upper bout, but are otherwise conventionally laid out. The X is attached to the soundboard at 5 points - the 4 points where the ends of the X meet the sides and in the center where the X crosses below the soundhole. The X is splayed out much wider than usual and doesn't cross the ends of the bridge (the fans give support to the bridge). I kept the X because I think it adds a lot of strength to the top where it needs it for steel stringing. I like the results I am getting, but I don't think it's particularly new or revolutionary. Try building one and see what you think.

Well, boys, I finally found a photo of my "A Class Bracing" done on a 12 string a long time ago. I suppose I could say that it had all kinds of qualities that no one would believe, but I will say that it sounded OK. Like I said in another thread, the problem with bracing that runs fairly parallel to the grain of the top, is that the telegraphing is horrid...and that top was red spruce in the .150-.160" range.



Frankly, the best bracing I ever used was "Larson Class Laminated X Bracing", with "Ladder Class Laminated Back Bracing", but I don't have the where-with-all ($$$$) to put out the BS, eh hype that would be needed to convince enough builders that it would be worth the risk, or at least the speculation like the "V Class Bracing" or "Virzi "tone producer". BTW, if I remember right, one of the Virzi bros was married to Lloyd Loar's sister or something like that. Hmmmm.
I would imagine I could find enough players to play my instruments and wax poetic about them while I spewed enough corporate doublespeak to mystify builders into speculating on everything, but as Mr. Gore suggested, "some customers prefer a less accurately intonated guitar, that's not hard to achieve". After all, that's what it is all about, right? Satisfying the customer. Some of them even prefer what most of you would call "dead strings". And in addition I have no truck with "note purity"...too sterile.
So, there you have it, the minor end of guitar building. Trying to improve the traditional and yet obscure...

I'm not understanding your explanation here, Brian. Apologies! We are trying to explain a frequency shift (as seen on a tuner). I can see phase shifting causing an amplitude modulation but not a frequency shift. What am I missing?


There is quite a bit of difference between an acoustic guitar and an electric guitar. An acoustic guitar is a set of coupled resonators which interact and cause all sorts of weird effects like frequency shifting. An electric guitar only relies on the string resonating and the pickup sending that signal to an amp. It would still work if the body and fretboard were a granite bench. (I know that strings and pick ups can interact, but I don't believe that's at issue here). So I think the systems are sufficiently different to allow for different root causes and yet also share some where the root cause is in a common component like an inharmonic string.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au