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  #121  
Old 03-09-2018, 12:52 PM
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Erithon Erithon is offline
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I've learned a lot reading this thread. This sort of lively and technical conversation is one of the many reason why I love the AGF.

I do think, however, that Andy's reply has become a bit misconstrued along the way. Picker2 wrote that:
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Originally Posted by Picker2 View Post
In this particular case I don't get why AP stated that if you fret the high E at the 12th fret (659 Hz), the fundamental will also resonate (329 Hz). It doesn't, and it never will.
(Picker2 also said something similar in post #55.)
But it seems to me that Andy is suggesting that a top with a natural resonance hot spot of 320Hz will resonate when either E4 or E5 is plucked (albeit for a short time as Picker2 has convincingly shown)--not that plucking E5 will somehow sympathetically or subharmonically excite E4 as well. In Andy's words: "If a guitar has a natural resonance hot spot around 320Hz, it will vibrate whenever either of these E naturals are played. But what we’ll hear is a mix of 329 or 659 and 320" (emphasis mine).
I still question some of his other claims, but I think it's important that we understand exactly what he is (or is not) saying and don't criticize him for claims he is not making.
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  #122  
Old 03-09-2018, 01:04 PM
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Originally Posted by KevWind View Post
I appreciate your spending an additional 3 seconds doing a test just for me. So Thanks
And yes I see that the frequencies below the fundamental with a rise look to be in the same location as those with the bridge tap very interesting, so I am guessing you are predicting the same would occur if you plucked the E string fretted at the 12
.. but we have only made it halfway to what I was suggesting . Where is the graph pluck with the E string fretted at the 12 th as per AP' statement ?
Kinda interesting to note the string pluck open high string you did does appear to generate the "Full spectrum" as you called it, and even produces rises below what the tap on the bridge does (which looks like "additional information") HUMMMMMM ????? It appears you were mistaken as to that being a reason not to test it .


Also it's great that you bolded your statement but your statement does not appear to be what AP actually said....
To clarify .......What he said (according to what you quoted him as saying) was ------

Andy wrote:
As an example, the E5 note on the high string at the 12th fret has a frequency value of about 659 Hz. An octave below is the open high E string at 329 Hz. If a guitar has a natural resonance hot spot around 320Hz, it will vibrate whenever either of these E naturals are played. But what we’ll hear is a mix of 329 or 659 and 320. That’s going to have a detrimental effect on what we get to listen to.
Ha ha ha, you're not easily convinced my friend! I like that, a good academic attitude . So: I decided to dedicate another 3 seconds of my life to you and recorded the response of the high E fretted at the 12th position:



As you see, the fundamental is now at 659 Hz. The 329 Hz (open E-string) is gone, as expected. AND, you still see the body resonant peaks at 108 and 190 Hz. They're always there, no matter what string you play and where on the neck you pluck.

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Originally Posted by KevWind View Post
Andy wrote:
As an example, the E5 note on the high string at the 12th fret has a frequency value of about 659 Hz. An octave below is the open high E string at 329 Hz. If a guitar has a natural resonance hot spot around 320Hz, it will vibrate whenever either of these E naturals are played. But what we’ll hear is a mix of 329 or 659 and 320. That’s going to have a detrimental effect on what we get to listen to.
As you see in my latest graph, my guitar does not have natural resonance hot spots around 320Hz, but it has two around 108 and 190 Hz. So you could argue that there is indeed a mix of 659, 108 and 190 Hz. HOWEVER, these 108 and 190 Hz do not produce distinct tones[/U]. They produce a 'thud' sound. Moreover, they only last a fraction of a second. So Andy's statement that this has "a detrimental effect on what we get to listen to" is not true. I repeat: what Andy states is that the sound of a bass drum has a detrimental effect on the notes played on the piano. Not true. (Unless it's a very bad drummer. )
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  #123  
Old 03-09-2018, 01:15 PM
Picker2 Picker2 is offline
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Originally Posted by KevWind View Post
BTW I have been meaning to mention your "White Lighting" piece is outstanding
Thanks! That was the same guitar I performed my pseudoscientific tests on today. It's one of the best guitars Taylor has ever built (albeit without V-bracing).



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  #124  
Old 03-09-2018, 01:26 PM
Picker2 Picker2 is offline
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Originally Posted by Erithon View Post
In Andy's words: "If a guitar has a natural resonance hot spot around 320Hz, it will vibrate whenever either of these E naturals are played. But what we’ll hear is a mix of 329 or 659 and 320" (emphasis mine).
Yes - you're right. I misinterpreted Andy's words there. Thanks!

But it makes no difference. The frequencies of the notes being played are irrelevant for the excitation of body resonant frequencies. So it does not matter if it's a 329 Hz or a 659 Hz, neither of the two will excite a body resonant frequency of 320 Hz. The only thing that happens is that the two frequencies will be released by the top at various sound levels, depending on the guitar's frequency response curve. If there is a peak around 320 Hz, the 329 Hz will probably sound louder than the 659 Hz, even when the string vibrates at the same amplitude for both frequencies. But it will still be a 329 Hz you hear ringing out, and no 320 Hz along with it. As stated before, the 320 Hz is excited only by the string attack and will merely produce a short 'thud'.

(In addition, of course, the hundred-thousand-dollar question remains: how could V-bracing consistently shift the 320 Hz hot spot to 329 Hz?)
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  #125  
Old 03-09-2018, 02:13 PM
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Quote:
Originally Posted by Picker2 View Post
Ha ha ha, you're not easily convinced my friend! I like that, a good academic attitude . So: I decided to dedicate another 3 seconds of my life to you and recorded the response of the high E fretted at the 12th position:



As you see, the fundamental is now at 659 Hz. The 329 Hz (open E-string) is gone, as expected (and unlike what Andy stated). AND, you still see the body resonant peaks at 108 and 190 Hz. They're always there, no matter what string you play and where on the next you pluck.



As you see in my latest graph, there is no peak at 329 Hz, as Andy claims. Of course not! The 659 Hz is there, obviously. My guitar does not have natural resonance hot spots around 320Hz, but it has two around 108 and 190 Hz. So you could argue that there is indeed a mix of 659, 108 and 190 Hz. HOWEVER, these 108 and 190 Hz two do not produce distinct tones. They produce a 'thud' sound. Moreover, they only last a fraction of a second. So Andy's statement that this has "a detrimental effect on what we get to listen to" is not true. I repeat: what Andy states is that the sound of a bass drum has a detrimental effect on the notes played on the piano. Not true. (Unless it's a very bad drummer. )
Hey Thanks and Yes thanks for being patient with my pedantic like questions .

OK seems indeed the octave below is not being reproduced,, but now (as per Erithon) looks like that was not what AP was saying. I admit the wording of his statement was a bit vague at first read


But now I have some new questions. First it appears you are using an iPhone app which one ? Because I now would like to see how my guitars graph
Not because I care about AP statements one way or the other, just curious about the body resonance .


Also after looking at the graphs and (understanding that an iPhone mic and graphing app. may not be the most accurate ) If that's what you are using ....

But couple anomalies appear to have arisen.

One: on the open E string pluck graph, Is the L Peak : number in the upper left , showing the fundamental or does (L) simply mean "loudest" ? ..If the fundamental, then why is it showing 331 instead 329 ? I certainly hope that does not mean your guitar is inaccurately intonated by 2 Hz ???? Maybe you need V bracing just kidding , I assume the (L) means loudest ??

Because in the new graph with the 12th fret pluck the L Peak is showing 1324 assuming that is twice the fundamental, if it's the fundamental, that would make that 662 Hz ..... so why is the octave above tone louder than the fundamental by what appears to be 3 or 4 db ?????????
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  #126  
Old 03-09-2018, 03:33 PM
TerryC TerryC is offline
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I always give my wife a hard time about watching reality tv, but considering how much enjoyment I get out of combing through threads like these, maybe I need to cut her some slack. But hey, at least I'm learning something along the way, right? This is the kind of stuff that makes AGF so addicting!
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  #127  
Old 03-09-2018, 03:37 PM
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Except that "reality TV" is anything but, Terry. It's mostly scripted and directed but without professional actors and actresses and writers.

Here at AGF we engage in a dynamic dialogue, just like any discussion among friends. Threads can take a turn in direction at any moment, and we all learn a lot more about our hobby -- more than who got voted off the island or who got a rose this week.
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  #128  
Old 03-09-2018, 04:11 PM
vindibona1 vindibona1 is offline
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Technically there is no such thing as sub-harmonics. That would be a lower fundamental, and the frequency you are interested in might be a harmonic of THAT. In the example of 110 Hz, the fundamental frequency would be 55 Hz and the first harmonic would be 110 Hz -- not the other way around. The harmonic might well be stronger in intensity than the fundamental. The relative amplitude of even and odd harmonics (harmonic series) is why a trumpet or a flute or a piano all playing a "C" note sound rather different.

My spidey sense always begins to tingle whenever someone says "sub-harmonic".



^^ This is where the proverbial rubber meets the road. All else is irrelevant.
I kind of grimmaced when I heard that "term" too. What was not presented clearly was the aspects of RESULTANT HARMONICS. You know, those pesky sounds that occur when all the fundamentals and ovetones vibrate in sympathy to the extent that they produce additional harmonics. [If you've ever been to a top flight brass choir concert, i.e. Chicago Symphony or NY Phil you'll know what resultant harmonics are.]

I played a presentation model the other day. It seemed to have a Taylor-ish vibe, but different. It was a nice guitar, don't get me wrong, but didn't blow my world away. That particular guitar sounded very much like a 714ce-cedar. Perhaps the upper frets had more sustain?
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  #129  
Old 03-09-2018, 05:01 PM
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Originally Posted by vindibona1 View Post
I kind of grimmaced when I heard that "term" too. What was not presented clearly was the aspects of RESULTANT HARMONICS. You know, those pesky sounds that occur when all the fundamentals and ovetones vibrate in sympathy to the extent that they produce additional harmonics. [If you've ever been to a top flight brass choir concert, i.e. Chicago Symphony or NY Phil you'll know what resultant harmonics are.]

I played a presentation model the other day. It seemed to have a Taylor-ish vibe, but different. It was a nice guitar, don't get me wrong, but didn't blow my world away. That particular guitar sounded very much like a 714ce-cedar. Perhaps the upper frets had more sustain?
Just to clarify so there is not confusion that "term" (sub harmonics ) was not used by Andy Powers rather by someone assuming that is what he was talking about.

The most dramatic example of a sympathetic harmonic vibration I have encountered is while standing next to (like reach out and touch ) 7 Burlington Northern locomotives ramping up to pull 50-70 freight cars out of the yard . It is just short of dropping you to your knees
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  #130  
Old 03-09-2018, 05:21 PM
Picker2 Picker2 is offline
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Originally Posted by Erithon View Post
I still question some of his other claims, but I think it's important that we understand exactly what he is (or is not) saying and don't criticize him for claims he is not making.
On second thought, Andy did make a statement about strings producing subharmonics. In the first post in this thread:

“The string vibrates at a pitch and is attached to the body, transferring its vibration to a larger surface which will try to vibrate at the same frequency. If the body were so tuned to vibrate at exactly the same frequency as the string, life would be great. However, along with the intended fundamental note, we have overtones, and to a weaker degree, undertones. These are mathematically related other pitches summed together with the intended pitch. If we looked at A 110Hz, we should also have 220 Hz, 330Hz and so on, as well as a half-formed 55Hz.”

Now I understand why I misinterpreted his argument about the E string fretted at the 12th string producing also an E4. I think maybe Andy confuses body resonances with string harmonics. In any case, an A string with fundamental of 110 Hz does not generate a half-formed 55 Hz like he states.
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  #131  
Old 03-09-2018, 05:21 PM
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Originally Posted by Picker2 View Post
Yes - you're right. I misinterpreted Andy's words there. Thanks!

But it makes no difference. The frequencies of the notes being played are irrelevant for the excitation of body resonant frequencies. So it does not matter if it's a 329 Hz or a 659 Hz, neither of the two will excite a body resonant frequency of 320 Hz. The only thing that happens is that the two frequencies will be released by the top at various sound levels, depending on the guitar's frequency response curve. If there is a peak around 320 Hz, the 329 Hz will probably sound louder than the 659 Hz, even when the string vibrates at the same amplitude for both frequencies. But it will still be a 329 Hz you hear ringing out, and no 320 Hz along with it. As stated before, the 320 Hz is excited only by the string attack and will merely produce a short 'thud'.

(In addition, of course, the hundred-thousand-dollar question remains: how could V-bracing consistently shift the 320 Hz hot spot to 329 Hz?)
Ahhhh... I see the problem.

Your wrong.

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  #132  
Old 03-09-2018, 05:24 PM
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Originally Posted by Picker2 View Post
It is always allowed to reach conclusions by scientific reasoning plus observations of one experiment to predict observations of another experiment - as long as you stick to generally accepted scientific principles.

In this particular case I don't get why AP stated that if you fret the high E at the 12th fret (659 Hz), the fundamental will also resonate (329 Hz). It doesn't, and it never will. That's the whole point of fretting a string. I assume it was just a slip of the pen, or maybe he meant it the other way around: if you hit the open E string (329 Hz) the first harmonic (659 Hz) will sound along with it. This is indeed true.

The recording of the body resonance after tapping the bridge may seem to be an odd thing to do, but it is a well-known method to capture the properties of acoustic systems (room ambiance, echo's, but also the tone of stringed instruments). The method is widely applied in digital audio processing, e.g., convolution reverb. It's a standard method and there are countless text books describing it.

There is no point in recording the string pluck to test the body resonance. The string pluck will only generate a very limited number of frequencies. It's like taking a picture through a couple of narrow slits - you will only see a small part of the total scenery. A short tap, however, generates all audible frequencies in one go and feeds them to the top. The top will then resonate with those frequencies it supports. Since the tap contains all audible frequencies, you can be sure you never miss one.

Regardless all of the above, my most important statement is that body resonant frequencies in a guitar are always so short and so unspecific that they will never interfere with the frequencies generated by the strings as they ring out. Since this is what the whole "better-in-tune-ness claim" of V-bracing is about, this claim makes no sense to me.
uh, what he said

I think everyone would have been able to swallow this better if AP just said, "they sound better" and left it at that.

then, it's just a matter of opinion, when one makes "scientific" statements about an aspect of a guitar, those statements are either true or false, if they turn out to be false, as time goes by and various people with the proper methodology dissect it, it just won't "look" good, regardless of Taylors successes.

but in the long run I don't think it will negatively effect them one way or another.

really it just gives us something to blather about.
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  #133  
Old 03-09-2018, 06:18 PM
KarenB KarenB is offline
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Folks are still going to make music on X-braced guitars, V-braced guitars and cigar box guitars. And people will still be moved by the music that touches them.

Best,
Jayne
Love this! Thanks.

Karen
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  #134  
Old 03-09-2018, 06:49 PM
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I have drunk the kool aid. Drunken the koolaid, drank from the koolaid? Not sure. But in respect for Taylor's patent I will forgo the V and do a fan brace instead. Don't want any pesky lawyers come knocking around at night.



Think I will go bend some sides.
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  #135  
Old 03-09-2018, 06:53 PM
jaymarsch jaymarsch is offline
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I think it is actually smoking the koolaid. LOL! Let us know how that fan bracing shakes up those resonant harmonics or sub-basement resonances, or overdrawn tonics. You get my drift. [emoji41]

Best,
Jayne
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