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RE: How can I make my guitar less noisy (in reply to Richard Jernigan)
quote:
ORIGINAL: Richard Jernigan
Among luthiers I have run across who have written about "scientific" experiments, Al Carruth has been the most prolific.
When he lived on the outskirts of Boston he had apprentices who studied engineering at MIT. Some of them provided him with info about technology that was useful in devising his tests.
Despite all the time and energy Carruth has devoted to the subject, he says, "With measurements we can tell good guitars from bad ones, but we can't tell good guitars from great ones."
All the makers I have bought from or admired have aspired to make great ones.
RNJ
I've been following Alan Carruth since his days writing about Carleen Hutchins (sp?) and the Catgut Society. Back then I was mainly driven by my interest in violins. One of my first teacher's apprentices also studied with Mr. Carruth. He makes really nice guitars.
Most makers I know are aware of the technical aspects of modern guitar making. Many regard it as not much more than a useful part of their toolkit. It's really up to the personality of the maker how far they want to go with that.
I don't know if I've ever met a serious maker who didn't aspire to make great guitars. A surprising large percentage of them succeed in this, so much so, in fact, that I sometimes wonder why some makers think they're so special or why so many guitarists seem to be incapable of objectively assessing an instrument without relying on the label. It's a tough business.
P.S. I may have been a little misleading in my earlier reply to estebanana, I actually do take notes and record the characteristics of the woods I use and also plate resonances, etc... The difference is I am recording the states of things after the fact. I don't have targets, I basically decide how to approach each piece of wood on its own, choose the thicknessing and bracing based on that, and select woods with a mind towards marrying the components. The record keeping is more for future use and also because keeping records just seems to be a good practice, in and of itself. I also learn from the process, and it keeps doors open.
Posts: 15725
Joined: Dec. 14 2004
From: Washington DC
RE: How can I make my guitar less noisy (in reply to Richard Jernigan)
quote:
ORIGINAL: Richard Jernigan
Ok, Pardon my bad physics but I should not have stated specifically "A 440", as that is like laymen slang for "my guitar is in concert pitch, not hippy 432 earth resonance A".
So the strong "A" frequency that honks is more "around 220". I just checked a chart to make sure my basic math is correct, but how the hell is F (87.3) or F# (92.5) have anything to do with this chart????? I don't get it guys. What my eyeballs are seeing is exactly the thing my ear is hearing in every damn guitar: ballpark 110, ballpark 220, and ball park 440. I am still scratching my head at the amplitude of those peaks and are some how NOT expressing a giant crotch Kicking A natural across the board????
I don't get it. Where are the charts that show strong peaks at 92.5, 185.0, and 370.0....the supposed "good" classical and flamenco guitars. Please guys, I still don't get it. Is that chart specifically for cheap build Cordobas or what????
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Posts: 3487
Joined: Jan. 20 2004
From: Austin, Texas USA
RE: How can I make my guitar less noisy (in reply to Ricardo)
I measured the leftmost peak on the chart on my computer screen, and converted it to frequency. My ruler is graduated to 1/2mm. I get 102.1 Hz. This is a few cents below G#2, well within the range of main air resonances I measured among guitars I owned at the time.
I would judge all of them to be excellent instruments, regardless of their main air resonances. Two classicals and two flamencas are among the very best I have played. Their main air resonances vary from a little below F# up to about 20 cents below A
What I see on the chart, from left to right are, the main air resonance, next is what Carruth labels as the "monopole or main wood resonance" at 223Hz (Just a few cents sharp of A3, and next:"long dipole." at 450Hz, about 39 cents sharp of A4.
So if you put this guitar into a PA feedback loop I would expect to hear a very slightly sharp A3 from the monopole resonance, since it is the highest peak on the chart. I would not expect to hear the main air resonance, since it is only one-tenth the amplitude of the other peaks.
Note that the vertical axis of the chart is in decibels. A resonance that is one major division higher on the chart is due to a motion of the top that is ten times as big.
I may have confused things in a previous post by saying the main air resonance was "down around F" when I had only eyeballed it as more than two octaves below A=440.
RE: How can I make my guitar less noisy (in reply to RobF)
Richard,
The issue is the spread of the chart, it’s way too wide to extract the information Ricardo wants to see.
When we look at the main air res ( I don’t know why I’m even mentioning this because I’m not a practitioner of this mumbo jumbo) we use a condensed slice of the chart, you’ve selected from Moscow to Kansas City, the slice you want is more like Hilo to Ponape.
I hope that helps 😆
I stopped doing this stuff, and I trashed all my saved sample charts when I became a tone gen atheist, but I can hold my nose and make a chart showing the F to A ( bass string) frequencies and how they stack up.
Really it doesn’t matter what the main air of or the main top resonances are as long as it’s not higher than A, and A is fairly dicey because it’s tense and nervous and it can’t relax. Most guitars are between F and G# and it really isn’t important is the guitar works and the player is happy with the sound.
The G on the bass E sometimes gets tangled up with other notes and feels slightly false ‘wolfy’- when that happens, see Pablo Requena video, it’s probably because the out board fan struts and the lower closing bars are too beefy and the bridge is too heavy and stiff.
Posts: 3487
Joined: Jan. 20 2004
From: Austin, Texas USA
RE: How can I make my guitar less noisy (in reply to estebanana)
The San Diego mechanical engineer is doing something quite different from Carruth's experiment. He's thumping with his finger on the bridge of a steel string guitar.
Carruth was working on a nylon string classical/flamenco. Competent builders would produce very different instruments.
Carruth was driving the top differently. He stuck a magnet onto it, and drove the magnet with an electromagnetic coil. The driving frequency was swept. The amplitude of the sound was recorded.
The San Diego guy was taking the Fourier transform of the thumped response.
If the thump had been a perfect absolutely instantaneous impulse, instead of a bass-loaded thump, the Fourier transform of the impulse and the swept frequency response would have been the same. But take it from a guy who was once one of the world's leading experts in radar signal processing, they aren't the same here. He would have gotten closer with his stick, but he didn't use it because the stick's own resonance would have been be audible to the microphone.
The muddy, bass loaded thump emphasizes the lower frequencies. Furthermore he advises not to hold the mic near the soundhole, and then goes ahead and demonstrates doing just that. Most directional mics have a strong proximity effect at that short a distance, further emphasizing the low frequencies. The bass frequencies of the main air resonance do not project as directionally as the higher frequencies. With all these effects he ends up with a chart showing the main air resonance as the strongest one.
The San Diego guy reminds me of Neal DeGrasse Tyson's video clip about "knowing just enough about a subject to think you're right."
EDIT:Looking back at Carruth's note I see that he is measuring the sound output from the front of the guitar. The mic is placed to pick up some energy from the soundhole, though it is several inches aside from direct soundhole axis.
My posts here have all been motivated by Ricardo's observations of reliably getting a PA feedback at frequencies much higher than the main air resonance.
That implies the the combined response of the PA system and the main air resonance is weaker than the combined response for higher frequency resonances. The parameter that's still undetermined is the PA system's response. Does it really roll off significantly above 100 Hz? If so, it will depress the loudness of everything that sounds below the pitch of the open 5th string.
Is that what's going on for Ricardo? We don't know enough to say definitively.
And like estebanana, I don't really care, since in my experience the pitch of the main air resonance is not a reliable predictor of the sound of guitars I have owned and measured.
RE: How can I make my guitar less noisy (in reply to Richard Jernigan)
I just bellow into the soundhole at the top of my lungs and see what flies out, lol.
Seriously, though, I think most makers just tap and then hum the note they hear into a tuner to get plate resonances and hum into the soundhole and grab whatever note seems loudest for main air. When you make a guitar you can tap and hum away to heart's content every step of the way and none of it's going to definitively predict anything. I mean you'll get inklings but, you're right, it's not reliable. The proof of the pudding's in the stringing.
The thing about building to targets is how do you know if the target is optimal? If somebody keeps records and notes the characteristics of their best results over time that could help but, by the same token, by the time they've built enough instruments to draw any conclusions they've probably moved past the need anyways. But again, it depends on the personality of the maker. There's no rights or wrongs here. To me it just seems like extra work.
Another point, which I think estebanana has been making, is if you build to traditional methods and shapes a lot of this comes for free. Use a good plantilla and sensible bracing and thicknessing and most of the good stuff is just going to happen anyways.
Posts: 15725
Joined: Dec. 14 2004
From: Washington DC
RE: How can I make my guitar less noisy (in reply to estebanana)
quote:
Using Audacity- go to around 7:00 mins and pick it up
Well I don't care what the computer shows. He taps the back at 16:00 and slight dissonance is heard under a loud as hell Bb!!!
Richard Jernigan:
quote:
What I see on the chart, from left to right are, the main air resonance, next is what Carruth labels as the "monopole or main wood resonance" at 212.7Hz (between G#3 and A3), and next:"long dipole. "
HUH???? Either I can't read a chart or he can't read his own chart. There should be a hundred ticks between 200 and 300 and that peak is about a quarter of the way over, ie around 225. I am sure if I heard that guitar it is the same honking loud A as any other guitar. My dad's Hauser is like you say, a bit flat around G# I would say (which is 207.7), but it doesn't sound to me like a sharp peak like that, more like a round hump from G to A with that G# being most prominent. I mean that is how my ear is "visualizing" the issue.
I am using the PA thing because it exaggerates the issue (physically manifests and needs to be dealt with). What I am saying is acoustically, in your bedroom, every single note you play whether it is in tune or not, will have that 220ish A note sounding prominently at all times. I have not ever heard a guitar with this quality lower than G natural. (196).
Back to the video that shows a peak on the computer at 96...that is not even F# it is like between F# and G I guess, and very low pitch....the prominent note in that guys' guitar was Bb (around 233), at least when he tapped on the back at 16 min. If my dog and a computer hear some other important strong note, it does not really matter is my point.
RE: How can I make my guitar less noisy (in reply to Ricardo)
quote:
ORIGINAL: Ricardo
quote:
Using Audacity- go to around 7:00 mins and pick it up
Well I don't care what the computer shows. He taps the back at 16:00 and slight dissonance is heard under a loud as hell Bb!!!
Richard Jernigan:
quote:
What I see on the chart, from left to right are, the main air resonance, next is what Carruth labels as the "monopole or main wood resonance" at 212.7Hz (between G#3 and A3), and next:"long dipole. "
HUH???? Either I can't read a chart or he can't read his own chart. There should be a hundred ticks between 200 and 300 and that peak is about a quarter of the way over, ie around 225. I am sure if I heard that guitar it is the same honking loud A as any other guitar. My dad's Hauser is like you say, a bit flat around G# I would say (which is 207.7), but it doesn't sound to me like a sharp peak like that, more like a round hump from G to A with that G# being most prominent. I mean that is how my ear is "visualizing" the issue.
I am using the PA thing because it exaggerates the issue (physically manifests and needs to be dealt with). What I am saying is acoustically, in your bedroom, every single note you play whether it is in tune or not, will have that 220ish A note sounding prominently at all times. I have not ever heard a guitar with this quality lower than G natural. (196).
Back to the video that shows a peak on the computer at 96...that is not even F# it is like between F# and G I guess, and very low pitch....the prominent note in that guys' guitar was Bb (around 233), at least when he tapped on the back at 16 min. If my dog and a computer hear some other important strong note, it does not really matter is my point.
Now you see why all this is a boner killer?
Imagine guitar players emailing you to talk about commissioning a guitar and they order you to hit certain frequencies of modes. There’s a well known guitar maker in Southern California retired early because he got sick of this stuff. He moved on to other interests.
RE: How can I make my guitar less noisy (in reply to estebanana)
quote:
for a good spirit bath El Chocolate. 🍫 I like his fandangos too.
Always good to hear him.
Talking of fandangos and of going to church, here's Manuel Vallejo. El Chocolate and he could have crossed paths in Seville. Though Chocolate says in interviews that his fandangos are influenced alot by "...aficionados who worked as street vendors, or in grocery stores or at the Cruzcampo brewery. My style of fandango has a lot of those anonymous singers whom I listened to in the taverns of La Alameda and La Macarena. "
Muerto tengo el corazon desde que moriste tú muerto tengo el corazon me llevo de noche y día llorando al pie de una cruz con la esperanza perdía
Y rosa te llamas tú yo me llamo pensamiento y rosa te llamas tú viviré con el tormento de respetar tu virtud rosa de mis pensamientos
Posts: 15725
Joined: Dec. 14 2004
From: Washington DC
RE: How can I make my guitar less noisy (in reply to orsonw)
Ole! Many aficionados don't like the "voz de velocidad" or whatever their description of the fast vibrato and melismas, but he was great IMO. I think it was his malagueña del mellizo is the one where Montoya introduced the Am chord and changed the formal structure. At least it was the oldest one I could find that broke the basic copla structure of chords.
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