Official Luthiers Forum!

Todd -

I have no experience with basses ( acoustic or otherwise) but I can think of a few possible reasons for heavier bracing, sides, etc.

1. Is the string height at the bridge larger than typical for a steel string guitar? If so, that would result in more torque on the bridge and top, and heavier bracing ( and a thicker top) would make sense.

2. Since the body is larger overall, the same bracing as a guitar would mean more top flexibility and more bridge rotation, more bellying, etc. This would be true in the short term, and also get worse over time.

As to the sides thickness, that might be a fragility (handling) issue rather than a sound thing.
If you had thin sides ( like a typical SS) , but a larger body - more body depth, and less side curvature - the sides would be more vulnerable to flexing and cracking from handling and and bumps on the sides. Also, because of the reduced curvature, it's not so difficult to bend thicker sides.

3. Last, extra mass would not hurt as much ( or at all) as with a guitar, because you're not looking for high frequency response in a bass. That extra mass (for example, a large, heavy bridge plate) might even make it sound more "bass-like".

For good low frequency response, low stiffness is more important than low mass. It might be important that the edges of the top be thinned, and that the lower bout braces taper and end before they reach the sides.


Phil

I haven't built an acoustic bass but I've got on that's currently in the design stages. I like your 17 fret neck. All of the abg's I've seen had the bridge waaaaaaay to close to the tail block. The one I've going to build is going to be based on my "LJ" body shape. The body is 21" long. The bass will have a 16 fret neck. My only concern with the......long necks is how it will "feel". I suppose it will feel like somewhat like an electric bass.


Re, bracing. I'm still pondering on it. The string tension is very close to a Bluegrass dread but.............(there's always a but), Basses usually have only one string played at a time. I believe to get any kind of (good) sound out of it it will have to be light enough to *almost* implode. You won't have to worry about the tone getting all muddy and compressed playing chords. A thicker bridge/taller saddle combo may help also. I'm thinking 5/8" bridge + saddle height instead of the "normal" 1/2". More volume could possibly be acheived by making a smaller amount of the top plate active than usual, (think about a Smallman Classical) but it could get thin sounding, especially since it's a bass. My client has a Martin abg. I'm going to look it over real good soon, and decide what I want to do different.

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