NorCalluthier -> RE: Bad notes in classical guitars (Jul. 15 2017 20:38:01)
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Hello Tom and Konstantin, Well Tom, you and I and Gene Clark and David Rubio, and undoubtedly a bunch of other guitar makers were all radio hams in our youth---and Jack Bogdanovitch has an advanced degree in electrical engineering. So why am I the only one using my modest technical back ground to try to get a better understanding of how a guitar works? I use an audio analysis program on my PC---still running Microsoft XP---an old freebie rock amplifier, a coil stolen from a relay, a freebie obsolete microphone, and a 50 cent magnet. And, oh yes, a couple of cheap loudspeakers. The Spectra Plus audio analysis program did cost money, but I would have mowed lawns to buy it, it's so useful. With this setup I can get an accurate "acoustic fingerprint" of a guitar, or any part of a guitar. I use it to select top, back, fingerboard and bridge wood, to determine just what thickness to make a top or back, and to adjust sound-box resonances to where I want them during the final voicing process. And there is no math other than arithmetic involved---I'm just looking at graphs. What's not to like? In the end it's how the player likes playing the instrument that matters, and so far I've been pretty lucky in that department. I've got extensive notes, with photos, on all of these processes---in .pdf format---and will email them to anyone interested. Just email me directly so that I get your email address: brian@lessonsinlutherie.com And Tom, I find that I need to sand off about ten thousandths from the tops of fan braces to make any significant change in the positions of resonances. To get the air resonance to drop it's more like 50 thou off the main back brace. That's pretty slow going with salt or 600 grit. Konstantin, the player has about a quarter tone of "wiggle room" to tune his guitar. Any further than that, and a different note is deadened by the resonance. Maybe I should read Robert's thesis now, since I'm right in the process of trying to solve the problems that he is talking about (:->)... Cheers, Brian
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