soundhole placement

[Dennis Duross]

ok obviously there are any number of factors at work here, but are there any guidelines with respect to f-hole placement?

What happens as you place the holes near or further away from the rims?

Or nearer or further away from the braces?

The only thing I've ever found was in the Benedetto book, where he says to keep the braces 1.625 away from the inside edges of the f-holes.

But he doesn't say what impact deviating from this will have.

Which I find annoying.

[Dave Stewart]

Dennis, about the most definitive comment I've seen was this one from Bill Moll in this library thread http://www.mimf.com/old-lib/soundhole_shape.htm

".......As a general rule Bill, what happens to the sound when the f holes are closer together at the top, or further apart?

Bill Moll - 02:13am Jan 30, 2002
Moll Custom Instruments
That question, and it's variables, have about a 20 page answer but, simply put, altering the proximity of the upper holes will change the amount of flexibility the chest area has, which has an effect on it's ability to respond to vibrations. Altering the proximity of the lower holes effects that area's ability to transfer those vibrations to other areas of the plate.
In a perfect world, ie; all other factors being equal, moving the upper holes a bit closer together, while moving the lower holes farther apart, should cause the top to be a great deal more responsive than the other way around.
You'll see this technique applied in D'Angelico's instruments, D'Aquisto's, older Gibsons, and several modern builders. "

Opening & closing the braces (ie the "X") can have other effects (eg more open = warmer??). If you change f-hole placement at the same time, well, .......
It's how the "quest" become somewhat endless.

You'll find other related comments in the library (& elsewhere)

[Michael Lewis]

Talk about variables. . . . . . You really wanna go there? It's all about resonant frequencies of parts and their interactions. The stuff of Alan Carruth's many illuminating posts.

Start with the air column (captive air chamber), the placement of the sound holes can effect the column longer or shorter depending on their placement. The longest column would be a sound port in the far upper bout side near the neck, and the shortest would be large sound holes near the bridge more or less equidistant from the ends of the body. This has effect on the resonance of the air, but then you also have the top and back resonances and how they function and interact. Graduation and arching of the plates effects the stiffness / flexibility of the plates and placement of the braces reinforces the areas they effect.

When you move a sound hole out of in you can change the flexibility of the top but you also effect some other areas of response, and it gets complicated from there. I like Alan Carruth's comment that guitar making is not rocket science, it is actually more complicated.

By the time you have made a dozen or so archtops you should have some intuition of what will work and what will not work so well.

[Dennis Duross]

Thanks for the replies. I had a feeling there would be no simple answer...