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I'm working on an OM-ish sized guitar, and have the braced top joined to the rim. I used spray adhesive to stick a dummy bridge to it, then FFT analyzed it. Without the back attached, I'm getting a peak at 169 hz, and a higher one at 396 hz. I can't recall, in general, if that lower resonance will rise or drop when I attach the back. 169 seems a bit low. And I'm wondering about the significance of the 396 peak. Any insights on this are much appreciated. Thanks! Ken

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Mountain Song Guitars www.mountainsongguitars.com

Hi Ken,

The top will encounter more air resistance with the back glued on. Therefore, the main top mode will move up. By how much is a crapshoot and depends on the stiffness of the back.

I've found as well that glueing the bridge on raises the pitch compared to it being taped or otherwise affixed. So I predict between glueing the back and glueing the bridge, the main top mode will move up at least 10-15hz, so I think you're good.

Let us know!

Perfect, thanks, med. Any thoughts on the higher freq peak? If the back was on, I'd think it was that. Heres a shot of the beast.


Ken Jones
Mountain Song Guitars

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Mountain Song Guitars www.mountainsongguitars.com

396 will either be a dipole or tripole I'm sure.

Looks good. Though personally I feel the soundhole reinforcements should be quite a bit more robust...

.02

Why is that? Not trying to be contrarian, but it's something I've been thinking a lot about lately. They started out arched like braces, but made that area super-stiff, and while I know conventional wisdom is that that area has little effect on tone, I don't entirely subscribe to that notion. I see them as serving a similar function as side reinforcements, to stabilize and prevent cracks around the soundhole. To that end, I wouldn't think they need arching in the sense of the other braces and their duty of maintaining the convex rigidity of the top. So I shaved them down, and that area did drop significantly in pitch, to a point where I was comfortable with it relative to the other areas of the top.


Ken Jones
Mountain Song Guitars

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Mountain Song Guitars www.mountainsongguitars.com

Not sure really. Basically so,he soundhole edges don't flop around. It's something from the Somogyi books that I thought made sense. I make mine 1/2" wide x 1/8ish thick..