Official Luthiers Forum!

Hi All

This is my first post here, I come mostly from the electric world of 4 strings. I’ve been playing with the idea of acoustic basses for a while, and recently built this:




It’s a fully acoustic 31” 4 string, 15.75” lower bout, x-braced, with both a top and back that have been pushed into a 15 foot radius by the bracing. There’s a K&K pure under the soundboard.

My goal was not to build a bass that can be used unamplified. This is an impossible goal unless the body is the size of a small car. I wanted it to have an acoustic volume loud enough to practise at home, and an amplified voice that was acoustic in nature.

As a first attempt at this design, I’m very very happy with how it turned out.

I’m now planning my next one which will have a fully carved archtop spruce top and would like to get the benefit of your collective wisdom about bracing, and arching.

The one I’ve just finished had a simple X brace, no scallops:



Just to repeat, I‘m not looking for acoustic volume. I want a bass that has a good volume for solo practise and which retains an acoustic voice when amplified.

For this next one with a carved top, I want to increase bass response if I can, and am thinking of doing the following:

Moving the bridge 1cm towards the nut, to open up the lower bout a bit more
X brace, no scallops
Carving the top as thinly as possible, or at least thinning the recurve as much as possible
Robust back and sides to conserve as much energy in the top as possible

Anyone care to throw mud? Any pointers?

Welcome to the OLG Honza.
No mud from this keyboard, nice job.
I'm not yet knowledgeable enough to give many pointers, I'm pretty green myself.

_________________
Measure Twice,

Karl Borum

Nice work and welcome to the OLF. No advice here either, I've never built an acoustic base.

_________________
Steve Smith
"Music is what feelings sound like"

I've built two acoustic archtops based on Bill Moll's generous advice on dimensioning, bracing etc. Some good info in the old MIMF lbrary. Likely not something you are looking to build based on your criteria. They are very large guitars with a 20" lower bout, 4" ribs and carved back and top. 34" scale. They keep up well in an acoustic jam and are also electrified. One with a humbucker and the other with a K & K. Both were X-braced following Bill's bracing advice. They are about as large a guitar as you would want to play before being tempted to stand them up!

Thanks Darrel, were there build threads for your two? They sound like a handful! I'm definitely not looking to go to 20" quite yet, but never say never

Here's another one from Sonntag. A bit smaller at 17". Looks like it should kick out a bit more bass, but I wonder in reality how much more volume? I've read elsewhere that top size creates the volume, and body depth creates the tone. Does that sound right to you?

I'm not smart enough to be able to answer that. I ust know what my ears hear. Heres a few pics including one showing the size difference from a regular 17" string archtop and a tenor ukulele in the background. Built pretty much the same as a six string but with the suspension bridge for lack of a better term, bracing as per Bill Moll. Blackberry pics from a long time ago so not too crisp. I'm not very good at progress pics.

Thanks Darrel for posting those. That's a really really great job. I love it. Very tastefully done. Can I ask what strings you have on it?

I actually had a bit of difficulty finding long enough strings after the fact without going to custom lengths. Elixer strings proved to be "just" long enough.