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Acoustic Bass Guitar


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Yup, I KNOW that an acoustic bass guitar needs amped to be heard againt anything louder than a pin tapping on a piece of tissue paper

I've built a bunch of acoustic guitars and mandolins (including a 6/12 doubleneck acoustic) so now I'm gonna have a run at an acoustic bass guitar.

I have a dread mould and a pile of nice walnut and cedar.......

so has anyone built a bass?

the net is FULL of pics of guitar bracing, but I can find very little on bass guitars.

the tension should be less than a 6 string so the bracing shouldn't need to be heavier than a standard dread, though I will move the bridge an inch or two farther from the heel to stop the nek heaviness.....

so, anyone built a bass and have pics?

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I don't think I've seen an acoustic bass on here yet. I have a walnut rim ready to go just for this, but its a very back-burner proj right now.

I was wondering myself about the bracing. Same issues (string tension, different bridge location). Does the MIMF have anything on that?

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I've made a baritone which required moving the bridge somewhat. To support it in it's new location I ended up using a combination of shifting the X a little, and a bigger, thicker bridge plate. It sounds great and there's no sign of any problematic lumps appearing.

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the tension should be less than a 6 string so the bracing shouldn't need to be heavier than a standard dread, though I will move the bridge an inch or two farther from the heel to stop the nek heaviness.....

so, anyone built a bass and have pics?

First: I have no experience from building acoustic basses so I should really just shut up. BUT, I saw a flaw in the above statement. An ordinary set of Daddario 12 - 54 acoustic strings have a string tension of 78.88 Kg. Their accooustic 45 – 100 have a string tension of 86.53, That is close to 10% extra. So you will have to take that in consideration. One more thing. The force from every individual string on the bass will be almost double (OK not really) and you might have to make the bridge much heavier to not split or be damaged. That will add to the weight and attenuate the output.

I have found some interesting discussions about acoustic basses. One of the most interesting was one were the builder tried to maximize the output by building the lightest most responsive top possible. How? By removing a string! A 3-stringer can be built much more delicate and might be able to provide the output needed to be heard without massive amplification.

Once again, no personal experience, only thinking out loud…

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Thanks for the sums Peter, OK, I need a whisker MORE bracing..... I can do that.....

Three strings?

Na, it's gotta have 4, and like I said at the top I'm not really that fussed about the acoustic volume as it'll alweays be amped

As to the MIMF, I really can't get on with the interface over there, and the antequated system has me pulling my hair out.

I had a glance and could only find archtop acoustic basses.

and as no-one has tried it before, I guess I should post pics as I go.........

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the tension should be less than a 6 string so the bracing shouldn't need to be heavier than a standard dread, though I will move the bridge an inch or two farther from the heel to stop the nek heaviness.....

I am not so sure this is correct. The tension of a standard set of 12's(6 string) will produce 160-170lbs(or there abouts). A set of acoustic bass strings(4 string 45-100) will produce 190-200lbs.

If you use a standard dred size top I would think you could use a basic x pattern(it is basically serving the same purpose). You will have higher tension and a lot more energy transfered to the soundboard. I would go a bit taller at the main x to beef it up, your transverse would be pretty rigid anyway(but little extra beef wouldn't be a bad idea). I don't think you will have trouble abdjusting the bracing to get good strength.

I might try using a slightly thicker or stiffer sound board to handle the extra energy without distortion. I would look to treat the outer rim to enphasize good bass movement. I would think about maybe increasing the width at the lower bout to see if I could get more effective volume from all that string energy. I would be tempted to add depth or maybe a stronger wedge to get a little more air volume and distance between the top and back(maybe make for better use of the air coupling). Might be worth thinking about re-tuning the size(larger or add some length to the hole by creating a tube to increase the area of the hole) of the sound hole to drop the resonant freq. vs a regular acoustics range.

I would also look to Acoustic bass instruments that produce good volume and sound, and try to pick up on the elements that make them work well.

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Maybe ideas-

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I guess thats about all I can add as I have not built an acoustic bass yet. I have been thinking about it for some time, but have not come to a final choice in design. I will not just mimic an overbraced 6 string when I do build mine. I figure we are supposed to try to build an acoustic as efficient and effective as we can, and 6 strings guitars are tuned for a different range of freq.

Have fun with it! I look forward to seeing what you come up with.

Peace,Rich

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Yup, Rich, lots to mull over there, but a guitarron?

it'd be like trying to wrestle a bath tub!!

I'm also toying with the idea of shortening the scale by 1 fret to drop the tension a touch......

some of those other links are great, but a pal from another forum posted me a set of bass bridge pins so it looks like a pinned bridge then!!

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I have asked the same question and gotten the same answers! I went out and bought a factory second (bridge placing incorrect) and looked it over. I did manage to get the bridge off. The bridge itself is bolted thru the top and secured against a bridgepad cut into a triangle shape that pulls against the X bracing.

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I have asked the same question and gotten the same answers! I went out and bought a factory second (bridge placing incorrect) and looked it over. I did manage to get the bridge off. The bridge itself is bolted thru the top and secured against a bridgepad cut into a triangle shape that pulls against the X bracing.

Some builders bolt through bridge plates(guitar or bass). It is not a requirement, but a personal choice. I would imagine you will continue to see similar responces. Mainly because the way a "acoustic/bass"(as in similar shape and dimensions to a 6 string guitar) as it has been built/ evolved it is not optimised for it's purpose. They were built more to accomodate the playability, and to look like a 6 string guitar. Acoustic guitars size, shape and design has been developed and evolved with quite specific acoustic tuning in mind. A bass operates at much lower frequencies, with more energy and a little more tension. The two instruments are functionally different and should have different dimensions if you want to get the most out of them.

Martin, I wanted to through "examples" of bass instruments and the guitarron is certainly functonal(as in works, I agree it is not something I wanna play). The most striking thing about most of these designs(at least to me). Is the depth(between soundboard and back), sometimes radiuses are much stronger, Necks seem to be closer to the box allowing the lower bout to stretch out a bit(generally at the cost of upper fret access, but heck do you really need crazy upper fret access on an acoustic bass), bridges seem to have a bit more mass. Some thoughts like going to more of a ladder configuration instead of an X brace config might provide better cross grain stiffness and allow for wider bouts. I dunno.... It is really new ground that does not have the kind of design refinement that you have with 6 strings. Time to get creative and think outside the box.

Peace,Rich

Edited by fryovanni
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my suggestions?

jumbo (gibson) size or even bigger if its possible.

long scale!

lattice (classical guitar) style bracing on steroids!

you should place the bridge in the center of the lower bout, not like some factories do placing them way back there.

just some things that should make your bass sound really good. and with some volume too!

that worked for me!

Edited by Hector
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Seriously, get used to the MIMF interface; the information's well worth it. It's faster, doesn't crash as much as this system, and what you really need to be doing is browsing through the library, which is indexed properly, linked, maintained and edited nicely so there's no useless chatter going on in between things. Use the catalog, NOT the search function (which is powerful but fiddly), and sniff through the sections you're most interested in. Honestly, you'll find a lot more expertise there than you will here, particularly if you're talking about acoustic instruments.

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Oh I know, but I'm on my 4th log in user name over there as the passwords don't work (and no I haven't just forgotten them!!!)

Don't get me started on them as I DO respect what they's doing, but it's as cumbersome as a supertanker in a swimming pool.

I understand,believe me. I don't personally deal with MIMF and thats is one of the reasons. That and some of the users were downright condenscending. Ask anyone here how to fix a trussrod, you get a decent informed answer. When I asked over there it was more than, "chuck it, it aint worth it." it was "why the hell are you even bothering with that piece of ....?!"

Sorry mates, I just like PG more.

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I find the OLF far more cumbersome than the MIMF - I hate scrolling past the ads to read *every* post. Still a great resource though.

I'm on my orginal MIMF password and ID, and have never had any trouble logging in. I suspect if you're having problems it's to do with your email account. If you bounce an email they send you (mailbox full etc) you'll get dropped from the membership roster.

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I like the idea of guitar-like acoustic bass. Surfing around for info/ideas, I came across a critique by William Cumpiano, luthier and acoustic guitar construction author. He might be overly cranky, because he's earned the right and likes to exercise it.

I'd try to maximize the body volume, as much as possible. There's a cello-ish acoustic bass, that might be the right size. Maybe use a wedge body (thinner on the top/bass-string side and wider on the bottom/treble-string side) to get an easier reach to the strings. I'm partial to an archtop design. Selmer gypsy jazz guitars had bent tops to form un-carved arches. Maybe a simple X-brace with a curved top... or even a bridge post (like on violins/cellos/d-basses).

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If you bounce an email they send you (mailbox full etc) you'll get dropped from the membership roster.

well THAT explains it!!!

like the idea of guitar-like acoustic bass. Surfing around for info/ideas, I came across a critique by William Cumpiano, luthier and acoustic guitar construction author. He might be overly cranky, because he's earned the right and likes to exercise it.

Cumpiano isn't cranky, you wanna cross Rick Turner!!!!!

think Simon Cowell from American Idol/X Factor....... you KNOW he's right, but BOY he rubs people up the wrong way to make his point!!!

I'd already read the Cumpiano article and I agree whole heartedly with all he says.

it's true. to get a BIG acoustic bass sound you need a HUGE box and preferable a way of constantly exciting the string........

that'll be a bow then.........

Hmmmmm have I just designed a double bass?

Like I said right up at the top of the thread, it'll always be amped so I'm making a dread body. I have the sides 1/2 bent, so when I get them done and in the mould I'll start posting pics.........

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  • 3 weeks later...
nice stuff man, nice stuff

just curious

did you shape the bracing?

yup, but I didn't get a pic before I stuck it all together.

looking at it nom the soundhole looks a little small. OK, it accentuates the large body, but I may open it up into the rostette before I permenantly fit the neck.

or not!!

it'll always be amped anywat so not a problem as far as volume is concerned.

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