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Plate Tuning using mode 5 and 2


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#1 Jonathan M.

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Posted 23 July 2009 - 08:57 PM

I am currently working on finishing my violin plates. I have made progress, however I am confused about the tap tone frequencies of mode 5 and mode 2.

Platetuning.org says the back should be 345 Hz for mode 5 and 171 Hz for mode 2. It also says the belly should be 328 Hz for mode 5 and 172 Hz for mode 2.

On the other hand, The Art of Violin Making by CJ and RC suggests 360 Hz for Mode 5 and 180 Hz for mode 2 for both the back and belly. Which reference should I use? Thanks

#2 Janito

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Posted 23 July 2009 - 09:34 PM

Hi

Does it matter?

ps - I confess that I wouldn't know a tap-tone from an aubergine.

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#3 grajki

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Posted 23 July 2009 - 09:38 PM

I am currently working on finishing my violin plates. I have made progress, however I am confused about the tap tone frequencies of mode 5 and mode 2.

Platetuning.org says the back should be 345 Hz for mode 5 and 171 Hz for mode 2. It also says the belly should be 328 Hz for mode 5 and 172 Hz for mode 2.

On the other hand, The Art of Violin Making by CJ and RC suggests 360 Hz for Mode 5 and 180 Hz for mode 2 for both the back and belly. Which reference should I use? Thanks



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#4 iburkard

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Posted 23 July 2009 - 09:54 PM

fun to watch at least:


#5 Anders Buen

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Posted 24 July 2009 - 03:50 AM

I am currently working on finishing my violin plates. I have made progress, however I am confused about the tap tone frequencies of mode 5 and mode 2.

Platetuning.org says the back should be 345 Hz for mode 5 and 171 Hz for mode 2. It also says the belly should be 328 Hz for mode 5 and 172 Hz for mode 2.

On the other hand, The Art of Violin Making by CJ and RC suggests 360 Hz for Mode 5 and 180 Hz for mode 2 for both the back and belly. Which reference should I use? Thanks

What does your plates weigh? Weight is likely to be at least as important as tap tones for the backs. The mode 5 in relation to mode 5 in old italians is about 2,3 so none of these references seems to be good on that point. The tops will proably be too thick in the centre if tuned like this.

And what is your preference for sound? And who do you expect to sell the instrument to? A top notch violinist, a decent orchestra musician or an amateur?
"If the facts don't fit the theory, change the facts". A Einstein

#6 Oded Kishony

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Posted 24 July 2009 - 07:15 AM

Collect as many plate tuning combinations as you can find, then calculate the average. You can't go wrong this way!

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#7 Jonathan M.

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Posted 24 July 2009 - 08:35 AM

My violin back currently weighs 120 grams and my belly is 90 grams because it is made out heavy Sitka spruce. I think i may need to remove more material on the plates especially the belly, does anyone have a good plate thickness map that is successful.

#8 Jonathan M.

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Posted 24 July 2009 - 08:40 AM

Ideally, I would be selling the instrument to a top notch violinist. But who wouldnt want to be?

#9 Johnmasters

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Posted 24 July 2009 - 08:50 AM

What does your plates weigh? Weight is likely to be at least as important as tap tones for the backs. The mode 5 in relation to mode 5 in old italians is about 2,3 so none of these references seems to be good on that point. The tops will proably be too thick in the centre if tuned like this.

And what is your preference for sound? And who do you expect to sell the instrument to? A top notch violinist, a decent orchestra musician or an amateur?

I agree with you, Andres. Stiffness, in other words, may be what is crucial for a back, but I don't have the facts.

Knowing both 2 and 5 would at least be a way to fix some relation of longitudinal to transverse stiffness in a plate... But the top has f-holes and a bassbar. This means that there are other ways to adjust that relationship.

That is why the back interests me more. I am starting to wonder if the shape of the nodal line of the ring mode might be used by itself to adjust the back.

Does anyone have any experience correlating the size and shape of the back nodal line for mode 5 in the back with the relation of modes 2 and 5?

OK..... maybe tap-tuning is out of fashion, but here is something that still seems to me to be a possible use for it.

#10 Johnmasters

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Posted 24 July 2009 - 09:17 AM

My violin back currently weighs 120 grams and my belly is 90 grams because it is made out heavy Sitka spruce. I think i may need to remove more material on the plates especially the belly, does anyone have a good plate thickness map that is successful.

You may have missed some previous posts. Mass times frequency-squared has the units of a stiffness. Removing a few powers of ten, .8 and 1.2-1.4 work for me for top and back. (mode 5)

Just find the mode frequencies and get your numbers. Pitches of F and F# for top and back work for me. That does not say anything about graduation maps, of course.

#11 Michael_Molnar

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Posted 24 July 2009 - 12:08 PM

Jon,

Download the two Strad articles by Joseph Curtin, "Tap-tones" and "Scent of a Violin."

http://www.thestrad.com/hdownloads.asp

You should also subscribe to The Strad.

Mike

Stay tuned.


#12 Johnmasters

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Posted 24 July 2009 - 02:35 PM

Jon,

Download the two Strad articles by Joseph Curtin, "Tap-tones" and "Scent of a Violin."

http://www.thestrad.com/hdownloads.asp

You should also subscribe to The Strad.

Mike

I tried several times a dozen years ago. I gave up, they did not seem to read their mail. (paper mail) If the editor sends me an email, I will subscribe. She seems to read the forum.
jmluthier@sbcglobal.net.

I think Mr. Curtin did the right thing to find out about mass. By the way, the stiffness of some of these Chinese tops is quite high. Many are stiffer than ANY top wood I have obtained from violin suppliers. They are as stiff as some Sitka I have used, but less dense.

I think maybe the suppliers had stock that had been picked through. At least such wood exists, but it may be grown in different conditions than most European wood and also may not be the same species. Most likely to me is that the Chinese are going into virgin timber growth.

#13 Ken_N

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Posted 24 July 2009 - 06:15 PM

I used the Harris numbers to try to figure out how stiff to go. I haven't handled an old Cremonese violin plate (or any but mine) so I have no idea. I ended up going quite a bit thinner. Seemed way too stiff. The tap tones didn't change that much, but with the lower weight the stiffness number dropped quite a bit. But it seems that other harmonics are added that weren't there when it was thicker. The tap tones are meaningless when the belly is attached to the ribs. All the peaks on the FFT of the free plate are on the troughs of the FFT with the ribs attached. I really don't know much about tap tuning, I just measured it. One graph is the free plate and the other is with the ribs.

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#14 Johnmasters

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Posted 24 July 2009 - 06:30 PM

I used the Harris numbers to try to figure out how stiff to go. I haven't handled an old Cremonese violin plate (or any but mine) so I have no idea. I ended up going quite a bit thinner. Seemed way too stiff. The tap tones didn't change that much, but with the lower weight the stiffness number dropped quite a bit. But it seems that other harmonics are added that weren't there when it was thicker. The tap tones are meaningless when the belly is attached to the ribs. All the peaks on the FFT of the free plate are on the troughs of the FFT with the ribs attached. I really don't know much about tap tuning, I just measured it. One graph is the free plate and the other is with the ribs.

edit (to hell with it)

#15 Michael_Molnar

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Posted 24 July 2009 - 06:34 PM

... .

I think Mr. Curtin did the right thing to find out about mass. By the way, the stiffness of some of these Chinese tops is quite high. Many are stiffer than ANY top wood I have obtained from violin suppliers. They are as stiff as some Sitka I have used, but less dense.

I think maybe the suppliers had stock that had been picked through. At least such wood exists, but it may be grown in different conditions than most European wood and also may not be the same species. Most likely to me is that the Chinese are going into virgin timber growth.


I wonder what kind of wood they use.

Can we get a sample to an expert?

Mike

Stay tuned.


#16 Johnmasters

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Posted 24 July 2009 - 08:36 PM

I wonder what kind of wood they use.

Can we get a sample to an expert?

Mike

It is not quite like red spruce which is also pretty stiff. At least the samples I have seen. But it is milk white and looks just like Norway spruce. I could take a piece out from under a fingerboard, do you know anyone who can tell from that ?

#17 Janito

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Posted 24 July 2009 - 08:54 PM

edit (to hell with it)


Shame I missed this.

It would be great to have a consistent record of the wealth of your experience on acoustics/plate movements and emulsion varnishes.

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#18 Johnmasters

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Posted 24 July 2009 - 09:24 PM

Shame I missed this.

It would be great to have a consistent record of the wealth of your experience on acoustics/plate movements and emulsion varnishes.

Hope this is not an ironic comment. Actually, I have spent a lot of time with the emulsions. The plate mechanics is something else. Most of what I have mentioned is latter-day FEA modeling and half-assed physics modeling. My own last violin was three or so years ago. I now know that I consistently made inflections too slight and not inboard enough. I think if I change this, I will get more body of sound.

In other words, experiment has paid off for me in my major field of interest; varnishes. Everything I am doing is in a previous thread with the name "emulsion varnish".

The edited bit was a comment about Harris's effective stiffness. I mentioned this long before that paper of his was published. It is a simple extension of the harmonic oscilator equation. Harris adds 25% of mode 2, but the number is much smaller than for mode 5, so the results are very nearly the same.

#19 Janito

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Posted 25 July 2009 - 08:51 AM

Hope this is not an ironic comment.


Absolutely not. The fact that I may not follow some of the more advanced modelling, for example, does not diminish the interest with which I read you posts.

If there is irony elsewhere, it's based on the notion that 'complex' measurements, equations etc can substitute for a good eye, common sense and good feel.

ps - There is a nice video of Mr S Zyg where I pointed out that folks should ignore the plate and watch his hands move over the plate.

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#20 Oded Kishony

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Posted 25 July 2009 - 11:10 AM

I agree with you that including mode 2 is more or less useless.

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