Well, I am gluing up the instrument. I decided to check the tap tones and weight of the plates beforehand. I used to use a great program for fft analysis called Sakuro8, or something like that. It doesn't work on Apple. I've tried to use Audacity because it will supposedly work on Apple, but I don't see how to get it to do anything. There is a panel, but nothing is active on it. It is merely an exercise in futility. I used my electronic keyboard instead. Anyone know how to get it to work? It isn't user friendly like the Japanese flute program. That one was great.
The back is about 102 grams, and the tap tones are fairly close to each other. The lowest is E3 then C4 and the ring note is Eb4. Almost an octave, with the the fifth a little high, and the octave a little low. The belly is harder to find the notes for. The low note is low; Bb2. Then the next note comes slightly more than an octave up at B3, so it is a semitone lower than the back there. The ring tone is elusive. I hear different notes depending on where I hold it. I hear a cluster of notes: E4, F#4 and A4. None of them particularly ring like the other two do. The belly is 75 grams.
Using the formula to gage stiffness we have 294 squared times 102 = 11.1 and, 370 (I used the F# a fifth up from the B) squared times 75 = 10.3.
They both seem to flex about the same to me. The edges are quite flexible, but the center is quite stiff. Maybe I could have gone thinner on the belly. Let's see what really stiff can do.
An opinion about the above belly tuning- 370hz squared and multiplied by the weight puts you close enough for the stiffness factor of the plate but let's assume the wood dries out some more over the next few years and then one day you decide to play the above mentioned violin on a real low humidity day. That 370hz will have lost a lot of moisture causing the plate to rise in frequency, possibly over the 400hz level, just my opinion though. The back supposedly will rise in frequency too but not as much as the belly. I did assemble one violin that had a higher hz back plate than I would of prefered but I'm going to assume it'll work because the belly is lower at 348hz. With that one I'm thinking a 15hz rise in frequency on dry days. That'll be paired with a back with a 364hz frequency. I'm thinking belly- 348hz + 15hz rise = 363hz. The back- 364hz + 7hz rise = 371hz. On the platetuning.org. frequency/compatibility graph for plates it should work. My suggestion Ken good buddy is to make your 4/4 plates with lower numbers than what I have here in this post. The above numbers are for a 7/8th sized violin which is about 3/4" or so smaller than what your probably making. If you decide you want to try to adjust/graduate an already glued up/assembled/playable violin of yours, make sure to do the back plate too because it's a drag just doing the belly and then realizing the back plate should've been checked too after gluing back together.
ReplyDeleteIf you Ken or anyone else that reads here what I posted, feel free to pick it apart- maybe I'll learn some more.
.... by the way, I had my son check out the platetuning.org website. He's one of those "computer geniuses" supposedly. I have no reason to doubt him. He's pretty sure he can get those audacity or other files to work for us but I need to go get a decent microphone for starters.
ReplyDeleteSounds good to me. I am going to tune the front and backs together. I'm stuck in roughing cello backs right now; but I have a violin, and a viola reday to do final tuning on. I even think that the final tuning could be after a seal coat, and with strings on.
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