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Octave Tuning for Violin Plates


pt3
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Hutchins proposed her famous "Tri-bi Octave tuning" method in the 1960s, namely, in graduating the violin plates trying to keep the frequencies in mode 5, 2 and 1 of the top plate in an octave relationship, and for the back just mode 5 and 2. I have tried to achieve this goal, and have found it is quite difficult. When the plates are thicker, (so higher resonance frequencies), this is easier, e.g., when M5 = 375Hz, I got M2 = 185Hz (top plate), with a weight of 84 grams. I continued to thin the plate according to Hutchins' graduation scheme, this octave relationship could not be met.

I wonder whether this "octave tuning" is really beneficial. Most of famous old violins do not have this octave relationship. Furthermore, Schleske pointed in his paper that no correlation between the resonance frequencies of free plates and the frequency characteristics of an assembled violin.

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Hutchins proposed her famous "Tri-bi Octave tuning" method in the 1960s, namely, in graduating the violin plates trying to keep the frequencies in mode 5, 2 and 1 of the top plate in an octave relationship, and for the back just mode 5 and 2. I have tried to achieve this goal, and have found it is quite difficult. When the plates are thicker, (so higher resonance frequencies), this is easier, e.g., when M5 = 375Hz, I got M2 = 185Hz (top plate), with a weight of 84 grams. I continued to thin the plate according to Hutchins' graduation scheme, this octave relationship could not be met.

I wonder whether this "octave tuning" is really beneficial. Most of famous old violins do not have this octave relationship. Furthermore, Schleske pointed in his paper that no correlation between the resonance frequencies of free plates and the frequency characteristics of an assembled violin.

I think this bi tri octave tuning is something she came to later in her career, say around 1980. her fiorst Scientific American article from 1962 put an emphasis on having a tap tone of the back plate about a half note higher than in the top. And she showed tap tones for a free Strad top and back. Acturally she showed spectra for the free top and back palte driven by a speaker coil attached to the plate and the magnet was inserted gently so as to drive the plate like a 'loudspeaker'.

I have gone trough Schleskes data and there are indeed correlations between the free plate data and the assembled violin, especially for the back plate. I have posted correlation plots of that some time ago here. There are however not a clear correlation in his data between the top plate mode 5 and the assembled violin which might have been a disappointment for him to see.

Both modes, plate weights, thicknesses and most of the mode frequencies correlates with the assembled violin mode frequencies for mode B1- and B1+, but also some of the others. The sensitivity between the free plates and the assembled violin is quite low though.

I think you should not let the mode 2 of the free top lie much higher than some 160Hz, around 150Hz might be better. That is my impression. Depends on the wood too to some extent.

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Hutchins proposed her famous "Tri-bi Octave tuning" method in the 1960s, namely, in graduating the violin plates trying to keep the frequencies in mode 5, 2 and 1 of the top plate in an octave relationship, and for the back just mode 5 and 2. I have tried to achieve this goal, and have found it is quite difficult. When the plates are thicker, (so higher resonance frequencies), this is easier, e.g., when M5 = 375Hz, I got M2 = 185Hz (top plate), with a weight of 84 grams. I continued to thin the plate according to Hutchins' graduation scheme, this octave relationship could not be met.

I wonder whether this "octave tuning" is really beneficial. Most of famous old violins do not have this octave relationship. Furthermore, Schleske pointed in his paper that no correlation between the resonance frequencies of free plates and the frequency characteristics of an assembled violin.

The M5/M2 ratio can be controlled by carefully selecting the areas to be thinned as the plate is being made lighter. Thinning outside of the mode node line raises the frequency while thinning inside of the node lines lowers it. If you sketch the your own plate's mode 2 node lines and mode 5 node lines you will see these areas. Attached is the diagram for a typical plate.

Marty

post-44223-0-10341800-1326118494_thumb.gif

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I wonder whether this "octave tuning" is really beneficial. Most of famous old violins do not have this octave relationship. Furthermore, Schleske pointed in his paper that no correlation between the resonance frequencies of free plates and the frequency characteristics of an assembled violin.

Only beneficial to the mind of the maker who likes to see numbers match up. You point out some logical and valid reasons why it doesn't matter. The only "evidence" that it does matter is Hutchins saying that it matters.

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I wonder whether this "octave tuning" is really beneficial. Most of famous old violins do not have this octave relationship. Furthermore, Schleske pointed in his paper that no correlation between the resonance frequencies of free plates and the frequency characteristics of an assembled violin.

I think the effect of octave tuning the top plate at that high mode frequencuy is that you get a relatively heavy plate and that the central part of the top tends to become thickish. Hutchins also made the ends of the plate thicker than the classic cremonese plates, what I call the 'Sacconi plateu'.

The effect of such a plate tuning on the violin is that you will tend to get a relatively stiff violin with high B1 modes and higher than what we usually find in good violins. The matching of the free paltes also will give such an effect. The low end will be tend to become too weak in comparison to good violins.

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This series of vidos have already been showed on maestronet. It shows the way violins and clavichord were supposedly made in the old times(18th-19th century) At about 6min on this

the maker uses a tuning fork and a bow to tune the plate.

There is a problem with this, as the plate is fixed in a vice or something like that here. The resonance frequencies will be affected by that, so this will not be the free plates vibrating. The mode shapes will be different too. But that method might be jst as usual (or useless) as any else method of tuning the plates if it is done the same way each time. That might give some information on the stiffness of the plates. But free plate data and data gotten from such a fixed plate will not be compareable.

Savart was said to use the bow to excite the plates and I have seen a rig for that apparently the clamp had rouynd edges and was holding the plate somewhat similar to how it is held by two fingers. The holding and tapping points will influence which note is heard. The same should be true for a bowed plate, except by bowing one only can excite the plate anywhere along its edges.

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Hutchins proposed her famous "Tri-bi Octave tuning" method in the 1960s, namely, in graduating the violin plates trying to keep the frequencies in mode 5, 2 and 1 of the top plate in an octave relationship, and for the back just mode 5 and 2. I have tried to achieve this goal, and have found it is quite difficult. When the plates are thicker, (so higher resonance frequencies), this is easier, e.g., when M5 = 375Hz, I got M2 = 185Hz (top plate), with a weight of 84 grams. I continued to thin the plate according to Hutchins' graduation scheme, this octave relationship could not be met.

I wonder whether this "octave tuning" is really beneficial. Most of famous old violins do not have this octave relationship. Furthermore, Schleske pointed in his paper that no correlation between the resonance frequencies of free plates and the frequency characteristics of an assembled violin.

After putting a tremendous amount of work into my first two handmade violins, I decided to use some in-the-white violins to experiment with plate tuning schemes and practice varnishing. In-the-white #2 violin was plate-tuned until the back was about a halftone higher than the top, and it sounded very good before varnishing, still good after varnishing. In-the-white #3 was bi-tri octave tuned AND the back M5 kept about a halftone higher than the top. After all that tuning, #3 doesn't sound quite as good as #2. There is no difference in playability, and very little difference in tone. I dropped the bi-tri octave tuning idea, got myself a Strad poster of the Titian Strad, and I'm starting with the Titian's top graduation scheme on in-the-white #4, then tuning it similar to the Kreutzer top data in J. Curtin's "Tap Routine" article... I've about decided that taptuning, stiffness figures, plate flexing and twisting, Chladni patterns, etc. are all just different ways to get to the same goal, which is how to tell when to stop removing wood from the plates. About all you can do is pick a method and experiment until you get the sound that you want, and don't be afraid to change methods if the one you're trying doesn't get you the results that you want.

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