5 string acoustic bass bass guitar

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JW Stapleton
Posts: 12
Joined: Thu Jan 02, 2020 9:32 pm

5 string acoustic bass bass guitar

Post by JW Stapleton »

Hi guys and girls! I am starting a project to construct a 5 string acoustic bass guitar modifying and using my dreadnought mold, I have constructed a few dreadnoughts but never a acoustic bass, so hopefully with you’re advise and opinions and know how I am hoping to be successful, my first question would be the best fret scale length to use? Second question would be what radius to use for top and back.

Carl Dickinson
Posts: 71
Joined: Fri Feb 08, 2019 5:38 pm
Location: Forest Ranch, California

Re: 5 string acoustic bass bass guitar

Post by Carl Dickinson »

I've built / building two. Both 34" scale on J200 body shape. First used a modified bracing pattern from Mark Stanley's plan to fit the 200 so the bridge was very low on the lower bout. Fret board / body at 14th fret. Bracing 5/32" x 1/2"or 5/8". The one I'm finishing now has a Martin 2nd neck, fret board and bridge. 19th fret neck / body intersect. Bracing is pretty close to the 200 plan by Micholetti from LMII. Top radius is 28 top, 15 back.
The first was shipped off to a grandson before I spent any time with it and I'm looking forward to hearing the next one. JJB 220 transducers in both.

JW Stapleton
Posts: 12
Joined: Thu Jan 02, 2020 9:32 pm

Re: 5 string acoustic bass bass guitar

Post by JW Stapleton »

Thanks! Great info! How deep is the body at the upper and lower bouts, I would love to see a headstock design to accept the 5string tuners and best truss rod to use. This info is very much appreaciated! East Indian rosewood for sides and back,sitka top, maple neck is what I plan to use.

Carl Dickinson
Posts: 71
Joined: Fri Feb 08, 2019 5:38 pm
Location: Forest Ranch, California

Re: 5 string acoustic bass bass guitar

Post by Carl Dickinson »

Forgot to say these are both 4 string ABGs so no headstock design for a 5. I'll measure the body depth when I'm in the shop tonite. I use two way Bitterroot truss rods lately.

JW Stapleton
Posts: 12
Joined: Thu Jan 02, 2020 9:32 pm

Re: 5 string acoustic bass bass guitar

Post by JW Stapleton »

thanks!

Carl Dickinson
Posts: 71
Joined: Fri Feb 08, 2019 5:38 pm
Location: Forest Ranch, California

Re: 5 string acoustic bass bass guitar

Post by Carl Dickinson »

5" at tail, 4"at neck, 1/4" over the plan. On the other I think it was 1/2" deeper than that because I had wider sides before bending.

JW Stapleton
Posts: 12
Joined: Thu Jan 02, 2020 9:32 pm

Re: 5 string acoustic bass bass guitar

Post by JW Stapleton »

great! how about a cutaway? I plan a cutaway in this one, it should not be a problem I hope! I am thankfull for youre info.

Alan Carruth
Posts: 1066
Joined: Sun Jan 15, 2012 1:11 pm

Re: 5 string acoustic bass bass guitar

Post by Alan Carruth »

With the deep sides a Smith/Manzer wedge makes a lot of sense. If you haven't done one before it's actually easier than it looks: all of the change is in the back, so the top and neck geometry is unaffected. Even a difference of an inch from treble to bass side is a big help, and the treble side only ends up 1/2" taller, so it doesn't usually cause problems with cases or obtaining side stock.

ABGs are not really standardized, and as a result there are several different string sets you can get designed around different scale lengths. The main thing is to figure out what the player can handle for stretches, and design around the strings that work for that scale. I made one a few years ago that turned out to be just a little on the long side for the player (at 28-1/4") and I had to make another. It worked out OK: it turned out to be one of my favorites of the ones I've made, and I now actually own one of my guitars.

That one is mahogany and WRC on a 16" small Jumbo platform. Sides run from 4-1/2" at the tail to 4" at the neck, with no wedge. It's a six string, designed around standard strings and a D-D tuning, but the player went to heavier gauge and tuned it B-B in standard intervals (so BEADF#B if I counted it right), and used lots of drop tuning intervals (such as 'DADGAD intervals becoming AEADEA; again, assuming I counted right) on top of that. I reduced the sound hole size to `3-1/2" to lower the 'main air' pitch, which doesn't actually drop much when you increase the body depth. '

On a more recent 4-string ABG along more 'normal' lines I actually used a larger hole, and added a sleeve to make it deeper, which dropped the 'air' pitch back down. I've got pictures of that someplace, if you're interested. The reasoning behind that was a bit complicated, and conjectural, but it did work out OK.

Bob Francis
Posts: 547
Joined: Wed Jan 11, 2012 6:28 pm

Re: 5 string acoustic bass bass guitar

Post by Bob Francis »

You might also consider a shorter scale say 32-32.5. As a bass player the body depth and scale length can be cumbersome.

JW Stapleton
Posts: 12
Joined: Thu Jan 02, 2020 9:32 pm

Re: 5 string acoustic bass bass guitar

Post by JW Stapleton »

I originally planned a 35 inch scale because my friend that I am building it for has a electric five string with the 35 scale, and my thinking is that he would be used to that scale but now that I am rethinking , the one I’m building will have the much wider body, which then may hamper the reach, I’m thinking I should get him over here with his electric and try to do some comparing, I think once this is brought to his attention and with a little expereminting he may want to go with a shorter scale, thanks for bringing this to my attention, thanks Alan for the rest of the info, though my little pea size brain may take a bit of study to comprehend a lot of the info

JW Stapleton
Posts: 12
Joined: Thu Jan 02, 2020 9:32 pm

Re: 5 string acoustic bass bass guitar

Post by JW Stapleton »

My sides are 5-1/2 at the tail and 4-3/8 at the neck , could I get a suggestion on soundhole size?

JW Stapleton
Posts: 12
Joined: Thu Jan 02, 2020 9:32 pm

Re: 5 string acoustic bass bass guitar

Post by JW Stapleton »

Pictures will be forthcoming as I get farther along, it may help for suggestions because I’m gonna need all the help I can get- thanks!😊

Alan Carruth
Posts: 1066
Joined: Sun Jan 15, 2012 1:11 pm

Re: 5 string acoustic bass bass guitar

Post by Alan Carruth »

Here is the instrument itself. It was designed as an electro-acoustic, with top transducers, so I didn't need (or want!) to have a string 'main air' resonance that would cause feedback issues. I used my 16" small Jumbo platform, and the walnut top also helps with that.
bass.jpg
I did want to use a large sound hole, however, to check out an idea I've had about the 'upper cuttoff frequency' of the hole. Basically, that's the point where the hole becomes very efficient at radiating power; a larger hole has a lower UCF. On bass reflex speaker cabs the diameter of the port can be chosen to fill in the mid-range or tweeter frequency, and since the gutiar is basically a bass reflex cab in the low range I thought I'd try to scale that pitch to the tuning range. But alarge hole gives a high 'main air' pitch, and I wanted to keep that down. That's the function of the sleeve: it drops the Helmholtz pitch without affecting the UCF, and also cuts down on the power of the 'main air' mode. Here's a shot of the sleeve being installed on the top.
sleeve.jpg
I made it by wrapping several layers of walnut veneer around a yogurt container, and added a thicker cross-grain rim that could be rounded off to reinforce the edge. I did some experiment on another guitar with cardboard sleeves to get an idea of the right height, and it seems to have worked OK. The hole in the sleeve is for truss rod access.

It's hard to say whether all of my theories worked out exactly the way I'd wanted; there's a lot to sort out on these things. The customer was happy, so it was a success where it counts... ;)

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