has anyone experimented with sound hole size?

[FRANK]

i am building an acoustic bass guitar and was wondering if i can in large the sound hole to almost 5 inch's for more bass projection?anyone please.and also beefing up the bracing

[Tim Mace]

I've been cutting a 4" x 2.5" oval into my Mandolas and really like the size/sound though I don't know at what point degradation sets in. Also easy access to the interior is a plus.

[Donald A. Fortune]

Hey Paul-- I make my sound holes on the dreads that I make, 4 inches and it seems to bring the sound out just fine-- Im in the process of making a dread size body for an acoustic bass and plan in using the same size hole..as far as the bracing goes I plan to use a lil larger than normal-- 5/16 wide X 9/16 high to give it more strength-- top and back are to be the same thickness tho (3 mm)
best to you on your build...
Donald

[Ron Frazier]

Try using your guitar as a experiment and tape over some of the sound hole and try it then more tape and try again until you cover all the hole. If you don't want to use the tape just cover with any thing and try. This wont tell you what happens if you make it bigger but it will tell you what happens to a change in size.

Ron

[Colin Brown]

Paul,

Although it would seem like increaseing the soundhole size and making larger braces would increase bass response, in reality the opposite is actually true. A larger soundhole and larger braces will actually increase treble response. A sort of analogy would be a potentiometer, the farther open it is the more treble is let through, whereas if you close it all the way all yo are going to have is lower frequencies. There is a lot of physics behind this that I am not familiar enough with the go into, but if I were building an acoustic bass, the first thing I would think about doing to increase bass response would be to make the body as large as possible while still being comfortable.

In terms of bracing though, it is sorta relative: if the body is larger you are going to need stronger bracing. But it's all about strength to weight ratios, as long as the bracing is strong enough for the guitar to stay together and be played, the less amount of bracing material, the better.

Think of an upright bass - comparatively small soundholes, very large body.

Ron's idea of messing with the soundhole size with something temporary also seems like a really good idea to me.

Good luck,

Colin

[Bob Webster]

Colin's got it right. A fellow named Helmholtz was the first to describe the relationship between hole size, body cavity volume and resonant frequency. Decreasing the hole size or increasing the body size drives the resonant frequency of the air down toward the bass. And, as we all know, stiffening the braces makes for a top that is more supportive of trebles and less so of the bass notes.

Cheers,
Bob

[mathieu thomas-guy]

If its a 4 stringer you can actually get a looser top as there is less tension on top, I would not go beefier. By going too large soundholewise you lose that "compression" effect that feel like bass, no wonder why bass cabinet are closed-back design. I'd built a 7 string archtop with a bigger sounhole and the sound comes out too quickly, if that make sense, we finally closed it a little and it was better, hope it helps.

[Mike Kolb]

One of my "one-of-these-days" projects is replacing the spruce top on a Tacoma acoustic bass and I've got a great piece of bearclaw spruce to use. The top's being replaced because of cracks which COULD be fixed but, -dang it-, I really hate the goofy tear-drop shaped soundhole that it came with! So here's an opportunity to relocate and/or resize the soundhole. Any thoughts or suggestions while still in the planning stages? ..thanks.