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rgwebb6

Tap tone for finished cello back

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I have found an article by Nigel Harris, "On graduating the thickness of violin plates to achieve tonal repeatability". Here are the frequencies (for cellos):

 

-back mode #5 -  142 Hz (C#-D)

-back mode #2 -  66 Hz ( C)

-back weight - 673 g (low 630, high 716)

 

"... resonance frequencies averaged over about 150 instruments made in our workshop to the thickness graduation method given in this paper".

 

I have made recently a 140 Hz for #5 and 53 Hz for #2; the wood was very heavy, so the finished back was outside Harris' reference data for his cello back. 

 

I would like to know opinions about this article and method, thanks!

 

--Giovanni

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Thanks for the responses, but I am totally in the dark when it comes to modes.  I hold the plate between thumb and finger in the upper left and tap in the lower right and seem to get an F tone.  Does that mean anything or am I just tapping in the wind.  It seem to have a nice ring to it anyway.  This is my first cello attempt and as hard as carving this back was it will probably be my only.

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Hi,  I wanted to check this thread again but I didn't have time this week.

 

This has helped me in finding the resonant frequencies: since the nodal lines in cellos are obviously farther from the borders I have tried to use a deep-throat clamp (the ones for gluing the bassbar) and small pieces of soft rubber, to support the back. Then I also made a small "hammer" with an eraser, covered with felt (taken from an old blackboard eraser). The eraser was tied to a thin rod.

Anyway, I have tried to stay near the figures in a "standard" thicknessing diagram (ex.: Henry Strobel), and I noted down the frequencies for future reference. I definitely need to make more instruments and experiment with different woods.

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