Light weight fiddle

[Roger Frankland]

a vertical deflection from say the B1 mode will result in lateral deflections and a twisting moment in the sides. Seems to me that the strength of the sides all around the perimeter will come into play in determining resulting amplitudes.

[Don Noon]

Yes, the ribs twist in the B modes.  However, the torsional stiffness of the thin ribs is not much.  Rather, I think the bending stiffness at the edge of the plate matters more, and that is where the corner blocks likely come into play, stiffening up the bending.  This is only related to the B mode frequency; the amplitude is much more obscure, relating to volume displacement of the mode, damping, and (probably more importantly) how well-coupled the mode is to the bridge and string.

[Roger Frankland]

Yes, the ribs twist in the B modes.  However, the torsional stiffness of the thin ribs is not much.  Rather, I think the bending stiffness at the edge of the plate matters more, and that is where the corner blocks likely come into play, stiffening up the bending.  This is only related to the B mode frequency; the amplitude is much more obscure, relating to volume displacement of the mode, damping, and (probably more importantly) how well-coupled the mode is to the bridge and string.

Makes sense to me. I just did another experiment. See my next post.

[Roger Frankland]

Removed, erroneous data

[uncle duke]

Are you going to try to get the plate to an acceptable stiffness index number?  With your numbers I get a 8754785 reading when, from what I've learned from others, it should be 8000000.   Marty would say to me "too many zeros".  And Mr. Molnar may be doing his figuring after ff holes are cut, lowering figures to a different area of numbers, though I'm not sure.  If you go these routes try not to lose the plates true ringingness by removing too much wood.  To early for me to tell if that comes into play later down the road or not.

[uncle duke]

I didn't notice it was a reject plate Roger. 

[Don Noon]

I tried something similar several years ago, with a soundpost support platform, and even attached a neck so I could play it.

 

Absolutely nothing useful.

 

 Edge constraints make a huge difference, and the edges of an instrument's plate aren't really "constrained" exactly... they're attached to the ribs/back, which make the whole issue lots more complicated.  Everything moves, and everything matters.

[Roger Frankland]

Exactly my conclusion, on top of which my data is not repeatable.

[Roger Frankland]

Well, today was the day. I strung up fiddle 7. Did not hear that magic resonance it had in the white. I spent the afternoon fussing with the bridge (Curtin's methodology) and moving the sound post about. Ended up with three out of four strings sounding pretty good. Now just the A string doesn't talk, but it did when the post was a touch to the right, etc, etc. This fiddle has 7 grams of varnish, including a heavy layer of burnt umber in the sound holes and pegbox. 7 grams does not seem excessive, thou It is more than I have used before. I will check the fiddle again tomorrow and probably hear something totally different. It has been raining all week and the humidity is around 65% which does not help. After listening to myself it is very clear that I should be practicing the scales instead of fussing with wood.

[Roger Frankland]

Now I have another idea... Bells! I was reading about the development of knowledge on constructing and tuning bells... Frequency inversely proportional to width, frequency proportional to the thickness squared. Sound familiar? Build somewhat oversized and tune down to pitch, remove material in strategic spots to bring into pitch the good overtones .. more familiarity. Build a clarion of bells to play a song .. Wow. I am going to make a "key of A" fiddle.

[Roger Frankland]

Spent the morning messing with the sound post on number 7. Ended up close to "spec" location resulting in a very nice warm sound. Great but not the bell like sound I am trying to get. Based upon sprectral analysis of the envelop of a bowed G scale, max amplitude is very close to 2khtz which is higher than the other fiddles on my bench and probably means something. And all the harmonics are even multiples of the fundamental but I suppose that is not a surprise. I surely haven't been able to measure warmness on a meter, only my ear does that. Fascinating. Time to mow the lawn.

[Roger Frankland]

On measuring resonances.. Perhaps it really is a lot simpler... In the first place, the sound generated in my fiddle is generated by the bow on the strings. The sound board (belly) simply amplifies the string sound. If the soundboard is too stiff, it will not do a good job, especially at the extremes. The tone will be harsh (just like what has happened to my voice after 70). If the sound board is too weak, it will generate extraneous sounds leading to distortions. The tone will not be clear (like singing under water).

Now, of course, there are other factors... But my problem has been that measuring resonances is easy to do, so I continue to search for meaning there, and get confused.

[Roger Frankland]

Back to fiddle number seven. Really nice tone in the white. Lost it after varnish went on. Got some of it back with a new soundpost. Next, replace the hand me down bridge I temporarily put on it.

Just reread "Violin - Making as it was, and is". The photograph of the violin by Andreas Amati (one of 24 made for Charles IX) is now my favorite ... clean, simple lines. ... no purfling, no chinrest. Go figger. I think I will research that further. I bet it was light too.

[Roger Frankland]

Still searching for an explanation why 3 grams (edited) of varnish on the belly significantly muted the fiddles tone. It certainly was not due to a shift in body resonances. Did an interesting experiment yesterday which convinced me. I took a reject belly I had sitting on my shelf, measured M5, then attached 3 grams of masking tape (4 strips) to the outside, and remeasured M5. M5 shifted from 367 hertz to 364 hertz, certainly not enough to cause what I heard!

Back to bending ribs.

[Don Noon]

3 ounces of varnish would kill anything; presumably you meant grams.

The weight alone of 3g probably wouldn't do too much, but the damping might.

[Roger Frankland]

Oops grams it is. The only way I seem to be able to measure damping is by listening with my ear. So I put 3 GRAMS of that masking tape on a belly and played a tune. yep , it changed from bright to muted. Funny though, the Audacity waveforms didn't look any different, so nothing to document.

[Roger Frankland]

Looked again. Taped the belly and looked at the response of a bowed 440A. I see a 3 or 4 db shift which would explain what I hear. Don't try this on a good fiddle, however, the tape can tear up wood.

[Roger Frankland]

Just strung up fiddle no 8. I am definitely improving as this fiddle (still in the white) has the best overall tone I have produced. The belly was carved from treated spruce with an SG of .29. Arching is 16.3 mm, channels are 2.5 mm. Graduations 2.5/3.0/2.6 mm. High speed of sound for low density wood ... 5111 m/s.

I was able to reach this low belly weight without resulting in any tubbing or wolf notes. The fiddle responates under the ear. I need to map the overtone patterns and eventually varnish it, but I think the tone will hold up. The treated wood is very stable, although a bear to carve.

[christian bayon]

Just reread "Violin - Making as it was, and is". The photograph of the violin by Andreas Amati (one of 24 made for Charles IX) is now my favorite ... clean, simple lines. ... no purfling,

Andrea Amati without purfling? witch one is it?

[Roger Frankland]

Andrea Amati without purfling? witch one is it?

doesn't say. The plate is not particularly clear so I could be wrong. But if purfling is there, it is very much in the background.

[Roger Frankland]

Just an update. I have finished varnishing fiddle no. 8. I now have two twins, fiddle 7 and 8, the ONLY difference being that no. 8 is made from processed wood (actually from the same tree) as fiddle 7. As a result, the belly on fiddle 8 is 10 grams lighter at 50 grams. The difference between the two fiddles is that 8 is louder in the low frequency region and sounds less harsh in the high end. I have been playing them daily, side by side and my preference shifts back and forth although I did accomplish my goal of reducing harshness. Both fiddles incorporate the same setups.

I have tried to measure the effects many ways. This is the best rendition I could make to depict what I hear.

[uncle duke]

Do you set the soundpost under the bridge or is it back behind some?

[Roger Frankland]

I have moved the post around a lot on both fiddles. I believe it is back about half the width of the post on both right now. I could measure if you are interested.

[uncle duke]

I have moved the post around a lot on both fiddles. I believe it is back about half the width of the post on both right now. I could measure if you are interested.

That's o.k Roger.  Just wondering.  I've been trying what the Heron-Allen books says while incorperatng D. Burgess' way of doing things.

[Roger Frankland]

It is a bit of a mystery. On my fiddles I have not seen as big an effect as others report, although right to left tends to shift the balance. As a result I center the post under the foot horizonally.