Chladni Patterns on my L-00 and SCGC 000

[Sam VanLaningham]

Hello all. OK I've been wanting to do Chladni patterns for awhile now, trusting Alan Carruth's belief that tap tuning spectra may not be as helpful as chladni patterns in determining how "good" or at least responsive a guitar is. Gore and Gilets book unified the thinking around the relationship between tap tuning and chladni patterns for me and thus the following data!

I looked at the chladni patterns on my own build, an Adi-walnut L-00 and my SCGC all mahogany 000.

I used audacity for tap tones and iOS app sig gen to move the black tea leaves.

The main tap tones for the L00:
main air - 104 hz
Main top - 176 hz
back - 220 hz and upper bout secondary peaks at 262 and 327 hz.

Chladni pattern frequencies that moved the tea leaves:
98 hz
183 hz
354 hz

SCGC:
main air - 108 hz
main top - 184 hz
back - 222 hz and secondary at 336 hz.

Chladni pattern frequencies that moved the tea leaves:
110 hz
195 hz
345 hz

Here's what I got. Seems like the L00 doesnt resonate much in the lowest lower bout but beats out the SCGC in getting more the top near the side edges resonating.........I dont understand the pile up at the bridge on the L00.

I would love to get all the feedback I can on these patterns. Thanks for looking. Sam

98 hz
DSC04092 by Sam Van, on Flickr

183 hz
DSC04090 by Sam Van, on Flickr

354 hz
DSC04091 by Sam Van, on Flickr

SCGC 110 hz
DSC04097 by Sam Van, on Flickr

195 hz
DSC04098 by Sam Van, on Flickr

345 hz
DSC04099 by Sam Van, on Flickr

[HikariGuitars]

Hello Sam! I'm also interested on the information regarding this!

Here, in the website posted bellow, I found the target frequencies for the top/back. According to the author,these values were taken from Gore/Gilet book!
I still don't understand how this whole "rocket science" works but I hope this topic and the more experienced can help us! (props to Alan Carrut).

Here's the link http://tommillerguitars.com/voicing/

Edit: Sam, I also found this very interesting piece of information. In this blog, Alan Lloyd has a table on how to inacrease/decrease monopole/dipole frequencies (although I still don't understand them, T,T) https://alanlloydguitars.wordpress.c...tar-acoustics/

[Alan Carruth]

The problem is that Chladni patterns on the assembled guitar don't tell you as much as you'd like. You have to mess up the structure pretty badly to not get the 'ring' on the top, and even the cross and long dipoles are pretty robust, in the sense tat you can almost always get them at some frequency.

Where I use Chladni patterns to advantage, IMO, is on the 'free' plates: the top and back before they're glued to the rim. This is controversial. The 'free' plate patterns and frequencies don't predict the lower order assembled modes in any simple way, and it is certainly the case that it's the assembled modes that count. However, I've got enough evidence linking 'free' plate mode shapes to perceived quality that I use them in my build process. It would be very difficult to 'prove' efficacy here. It would help a lot of we could get to the point where we can make 'identical' guitars that actually sound the same, and perhaps eventually that will happen.

The assembled patterns do, of course, tell you what part of the guitar is producing which peak in the spectrum, and that's helpful. The pitches of those peaks have some bearing on the timbre of the guitar, of course. The mode shapes can give you some information on the effective area of the modes, although that might be trickier that it seems. You can use them to track the effects of changes such as adding mass or shaving braces.

[Sam VanLaningham]

Originally Posted by Alan Carruth

Where I use Chladni patterns to advantage, IMO, is on the 'free' plates: the top and back before they're glued to the rim. This is controversial. The 'free' plate patterns and frequencies don't predict the lower order assembled modes in any simple way, and it is certainly the case that it's the assembled modes that count.

Hi Alan - Man, thanks for posting. Indeed I've read 5 zillion posts by you on the subject and I do trust your experience on the free plate aspect. But in the past year as Ive tried to wrap my head around resonant frequencies and patterns I couldnt fully inuit the meanings. Gore and Gilets book showing relationship between tap tones and chladni patterns on completed guitars helped push me to target some frequencies to see results. And now that Im a savvy vet (hehe) Im going to look at the patterns on free plates of the future and pull off some Carruth Tuning!

Originally Posted by Alan Carruth

The assembled patterns do, of course, tell you what part of the guitar is producing which peak in the spectrum, and that's helpful. The pitches of those peaks have some bearing on the timbre of the guitar, of course. The mode shapes can give you some information on the effective area of the modes, although that might be trickier that it seems. You can use them to track the effects of changes such as adding mass or shaving braces.

So you really dont think that how far out towards the edges the patterns reach is indicative of how much of the top is contributing to the volume/tone? And dont you think the fact that the pattern of the ring+ on my L00 not being too defined toward the end of the guitar means something? Such as the top is too thick, too thin or tone bar braces are too thick?

Anyways, I look forward to seeing patterns on the free plates coming soon. I hope you get to see them and help me out.

Sam

And here are some patterns on my newest build, Lutz-Pernambuco. Looks to me that this one is resonating better than either mine or the SCGC, yes, no?

100 Hz
Untitled by Sam Van, on Flickr

186 hz
Untitled by Sam Van, on Flickr

213 hz
Untitled by Sam Van, on Flickr

330 hz
Untitled by Sam Van, on Flickr

440 hz
Untitled by Sam Van, on Flickr

[Alan Carruth]

Left of Sam asked:
"So you really don't think that how far out towards the edges the patterns reach is indicative of how much of the top is contributing to the volume/tone?"

That's not what I said. What I'm saying is that you WILL see a closed ring on any guitar top that isn't totally messed up, and that it's presence is no predictor of the sound.

Gore goes into the physics behind his practice of adding mass to the sides to move the nodes out, and it's right on. He's talking about location of the node relative to the perimeter of the top, which has far more to do with the mass of the sides than it does with the top.

[Sam VanLaningham]

Originally Posted by Alan Carruth

That's not what I said. What I'm saying is that you WILL see a closed ring on any guitar top that isn't totally messed up, and that it's presence is no predictor of the sound.

Gore goes into the physics behind his practice of adding mass to the sides to move the nodes out, and it's right on. He's talking about location of the node relative to the perimeter of the top, which has far more to do with the mass of the sides than it does with the top.

Sorry Alan, I was lazy with my words/thoughts. I was thinking that because you did not have comments specific to these chladni patterns that I'm showing, you might not think there's any value in them/impossible to draw any conclusions etc.... .so then I jumped to a more broad conclusion that was false.

But the point about gores heavier sides discovery clarifies for me that if indeed we saw ring+ patterns further out towards the edges on assembled bodies, it's likely more a fcn of side thickness.

Ok thanks for your thoughts.

Sam

[Ned Milburn]

How do you "tap" the air...??

"The main tap tones for the L00:
main air - 104 hz"

[Alan Carruth]

Ned Milburn asked:
"How do you "tap" the air...??"

Well, let's see...

When you tap the top it moves in and out, and drives air in an out of the sound hole. That's actually part of a 'bass reflex couple' between the top and the Helmholtz air resonance, and the pitch you hear tends to be the 'air' pitch. Being lower in frequency than the associated 'wood' pitch of the top, and also quite strong, the air mode sound masks the top tap tone. You can hear the top and back tones by themselves (more or less) by blocking the hole with your hand as you hold the guitar up by pinching the upper transverse brace and fingerboard end between your fingers and thumb. Try to not touch the top (just try! )

Most of the 'higher order' air modes are harder to hear, in part because many of them don't 'talk' with the sound hole. They can affect the way the top vibrates, though, and thus alter the sound even if you can't hear them directly. My violin making teacher did experiments where she filled the body of a fiddle with CO2 or Freon to alter the air mode pitches, and measured the changes in the sound. Since those gasses are heavier than air they'd more or less stay put while you played a violin, since the holes point up, so it was possible to play the instruments and hear the results, as well as making measurements. They wanted to try helium, but nobody could play the fiddle standing on their head... It would be fun to try those experiments with a guitar some time.

Sound ports can 'listen' to internal air modes that the regular hole misses. Ports up at the base of the neck, for example, put out a lot of sound from the 'A-1' air resonance. This is a mode where the air can be seen as 'sloshing' along the length of the box, usually at around 350 Hz. Opening a port that can tap into that shifts the pitch up a bit, and you can see a prominent peak in that range on any guitar that has ports in that location. The same should hold for those guitars with the sound hole up in the corner of the upper bout. Again, if you tap on the top, it can drive that mode, and vice versa.

At any rate, we know much less about the air resonances of the guitar than we do about the wood, and that's little enough.

[CoolerKing]

Totally off topic, I really dig your L-00!

[iim7V7IM7]

I recommend that you invest $15 to buy this Chladni presentation from Mark.

http://www.blanchardguitars.com/guit...hladni_buy.php

[Sam VanLaningham]

Originally Posted by iim7V7IM7

I recommend that you invest $15 to buy this Chladni presentation from Mark.

http://www.blanchardguitars.com/guit...hladni_buy.php

Hi - What did you like about this pdf?

Sam

[Sam VanLaningham]

Originally Posted by matthewpartrick

Totally off topic, I really dig your L-00!

Thanks Matt! Looking forward to bursting the new one I'm building.

Sam

[Sam VanLaningham]

Originally Posted by Ned Milburn

How do you "tap" the air...??

"The main tap tones for the L00:
main air - 104 hz"

Haha Ned. I think you are mostly joking around, yes?

BTW, sometimes I listen to a lot of guitars on Dreamguitars website. However, I dont listen to too many classicals. But one caught my eye and ears. I take it you built this guitar? Wow. Nice. Very nice....

Sam

[iim7V7IM7]

Originally Posted by Left of Sam

Hi - What did you like about this pdf?

Sam

Mark takes you through how he applies the technique to his building process in a very practical and digestable way. He learned from Alan C. at course he gave 19-years ago. This was a talk that he gave at the Healdsburg Guitar festival about 8-years ago. He uses the technique to tune free plates unbraced and braced (top and back). He also speaks a bit about the limitations of what you are attempting to do on assembled bodies. It is a bargain for $15...

[Ned Milburn]

Originally Posted by Left of Sam

Haha Ned. I think you are mostly joking around, yes?

BTW, sometimes I listen to a lot of guitars on Dreamguitars website. However, I dont listen to too many classicals. But one caught my eye and ears. I take it you built this guitar? Wow. Nice. Very nice....

Sam

Nope. Those are different Milburns. I don't think they are building anymore, but am not sure.