Introduction: Acoustic Guitar to Acoustic Bass Conversion

Picture of Acoustic Guitar to Acoustic Bass Conversion
This instructable was made to convert an acoustic Guitar to Acoustic Bass.

You may be asking yourself why anybody would ever want to turn an acoustic guitar into an acoustic bass. Well I can’t answer for anybody else but for me it was because I had an old acoustic guitar lying around. So why not turn a guitar into a bass.

Sorry my camera has horrible audio. It sounds really good in person.

Step 1: What You Need

Picture of What You Need

This is a fairly simple conversion and you do not need many tools. What you will need however is:
Grinder or dremal
These tools may vary depending on your guitar

You will also need:
Scrap Metal
Guitar (of course)
bass strings

For me I had an old guitar that was given to my dad a many years ago. It looked like a cheap guitar and had been sitting in storage with the strings on so the top was peeling away from the body. If you are lucky you may find an old guitar lying around or i am sure you can find an inexpensive one on eBay. I have seen them go for very little. But if you are going to go through that to buy one, you might as well just buy a bass.

Step 2: Take the Guitar Apart

Picture of Take the Guitar Apart

You will now need to take your guitar apart. First, take the strings off. Then you will have to take the tuners off. Then the guitar strap holder .Depends on what type of tuners you have but hopefully you can take two of them off. For me I unscrewed a screw and it pulled right out. The Tuner peg you use for your low E string will also probably need to be drilled out, mine did.

Step 3: Nut

Picture of Nut

The string spacing on a guitar and bass are completely different. You can buy a new nut if you want but all i did was file a new slot for the two middle strings A and D. I also used the same groove for the Low E string and the G string, the low E string may have to be filed a bit bigger but it should not have to move.

Step 4: The Tailpeice Part 1

Picture of The Tailpeice Part 1

The hardest part of this build is definitely the tailpeice. I recommend that you start with a template. I used a piece  of construction paper to sketch it on.
To find the correct place to put the holes place a straight edged yardstick from the E string groove on the nut to the place where the old E string hit the saddle there should be a slight mark. Place a piece of paper on the guitar where you want your tail piece to be. Then follow your edge to the paper and mark it. Do the same for the D string.
Now with your two marks you are going to measure between the marks and divide by three. Then you found the places for the string holes. I then measured 3/8" from the edge and thats where the holes need to be.
The Holes to hold the strings were made by drilling a 1/4" hole and the connecting it with an 1/8" hole. the hole on the side is 1/8" also.

Step 5: The Tailpeice Part 2

Picture of The Tailpeice Part 2

The tailpeice I made is of 2 pieces of eighth inch stainless steel and a steel hinge. I used a grinder to cut the shapes out for these, you could also use a dremal tool, then use a MIG welder to secure them together.
I drilled a  hole in the hinge and then welded on top of it together.

Step 6: Put It Together

Picture of Put It Together

Now that you have made all of the pieces it is time to put it all together. First,put the tailpeice on. I recommend that you place a piece of cloth or other soft piece in between to protect the guitar. Then tighten it up. Four of the six tuners will need to be put on. You can put all of them on if you want, but for mine I put the top two and bottom two tuners on. This will mean that there will be two holes in the middle. I did not do anything with these holes but it you really wanted to you could fill them in with wood filler or whatever else.

Step 7: Stringing

Picture of Stringing

Now simple put the strings on. It's pretty straight forward.
The strings need to be tightened up all at the same time to keep the tail piece from pulling too hard on one side.

Step 8: Adjusting

Picture of Adjusting

I had to do a lot of adjusting to make this bass work well enough to be called a bass. The first thing i had to do was raise the bridge up about an eighth of an inch. This was done by placing 3 zip ties cut to the right size and placed in the slot for saddle. I also had to file a groove for each on the strings to sit in on the saddle. This kept the strings from buzzing.

Step 9: Future Improvements

Picture of Future Improvements
Future Improvements
     Make the tailpeice go closer to the saddle
     Put nylon string on
     Pull the frets
     close up the two empty hole on the headstock
     put something over the six holes on the bridge

If you have any improvements that you can think of add it in the comment, please. 
That would be great.


aaron0420 (author)2017-04-25

nice! I've been looking for instructions to convert my old acoustic guitar to a bass guitar. worth the try though I'm not good with measurements. thumbs up!

atroiano2 (author)2016-02-24

Played a U-Bass at the store and wondered why no one makes a parlor sized acoustic bass. Saw this able and got inspired. There are enough expired acoustics in the world to give this a shot. and wouldn't you know it, I have a welder.

who___cares (author)2013-03-23

I am planning to built one myself and got a question. Can't you just use the old bridge? Of corse by drilling two new holes.

DanielL26 (author)who___cares2015-05-07

I know this is very old, but for anybody who comes by and has the same question: you can't, because the intonation would be way way off. Even a short-scale bass guitar is way bigger than a standard guitar.

shamysmyth (author)2014-08-25

im kinda new to mods. the only thing i can do is to change the pickups (if you call that modding)..... but, do you not need a new bass neck ???

john.latorre.10 (author)2014-07-28

You had me intrigued enough to give this a try. I started with a home-built dreadnaught that had seen better days ... had some ugly patches, etc. I did a few things differently from you.

First, I removed the old bridge and installed a new one. To do this, I took off the back of the guitar and removed the original bridge plate, and replaced it with one that was about 50% thicker and 100% bigger. Before I replaced the back, I installed a JBB double piezo pickup, just in case the finished guitar wasn't loud enough for jams. In retrospect, I probably could have used your tailpiece set-up instead, since using a pin bridge didn't result in the volume I needed, and it turned out to need amplification anyway. And you don't need to remove the back to install the pickups, saving you a lot of work.

Second, I used bass tuning machines. I picked up a set for $20 or so at a music shop.

Third, I used a set of strings for a 5-string bass. The thickest string was .045", which would produce a B note on a typical long-scale (34") bass. I figured that on a short-scale (25.5') guitar, it would be like fretting on the fifth fret, giving the usual low E of a bass. The "E" string in the set would be used for the "A", the "A" for the "D" and the D for the G. The supplied G string would not be used.

I did have to drill out the tuner for the E string so that would accommodate an .045" string, and expand the slot.

The result was a bass that sounded pretty good, although soft in volume. The original strings were phosphor-bronze, which gave a louder, clearer tone, but when I played "plugged in" the finger noises were really apparent. I replaced the strings with half-round strings, which resulted in less finger noise but also less volume and clarity. Not a problem when you're playing with an amp, but I really can't jam "unplugged" with it, since the other instruments are louder. But plugged in, it gives a very sweet tone.

mdwheels03 (author)2014-04-22

Can you still put a strap on the bass after taking the strap holder off? Or is there a way to put a new one on?

auciel01 (author)2013-08-07

SO AWESOME! Thanks so much! TOTALLY doing this!! Quick question - when you filed the slots in the saddle for the bass strings, did it damage the saddle, or would i be able to put guitar strings back in? Thanks so much!

kosins95 (author)auciel012013-08-09

Yes it did damage the saddle. Unfortunately this mod is kinda permanent.

savvas_papasavva (author)2013-04-20

That's a nice mod, I've been thinking about doing something similar but was not sure if the neck of the acoustic would bend under the tension of the strings.

ArtieWallace (author)2013-03-22

I started out trying to learn the acoustic 6 string guitar and was not able to get the hang of it due to nerve damage in my hand. After a while I decided to try a 4 string Bass, that worked out much better for me. Sense then I been looking to turn my old 6 string acoustic into an acoustic bass. Everyone I spoke to told me “don’t waste my time trying to convert it”. Your instructions answered the few questions I had and could not figure out.

Thanks for posting on Your photos showed great detail and your instructions appear to be very basic. I think you answered the few questions I had, I will be trying to make the conversion and I will post how it worked.

Thanks again for sharing,

jackf (author)2013-01-04

How do you think it would hold up on an old 3/4 length nylon? too much of a stretch?

djframe (author)2011-12-14

what did u do to the neck? I did not see an explanation in the steps.


TheJoshinator (author)2011-10-23

If you can figure out how to adjust the truss rod in the neck, you might be able to use the B, E, A, and D strings from a 5-string set and tune them to a standard EADG. The thicker strings would require more tension for that tuning, as well as being shorter, and might be just tight enough to really be playable. You could also remove or grind down all the frets and just leave it as a fretless acoustic, thereby fixing your intonation issues

zombeastly (author)2011-08-28

VERY VERY COOL!!!! is there any way to do this to an electric guitar?

rimar2000 (author)2010-11-25

Nice work, well done.

"If you have any improvements that you can think of add it in the comment, please." I suggest you to change the plastic nuts (under the strings) with another made of bone. It is not difficult, and sounds a little better.

mdog93 (author)rimar20002010-11-25

also, it looks like thae action is too high on this guitar, that's the distance between the strigns and the fretboard for those who might not know.

Was this a steel string to begin with? and also what did you use the welder for?

oh and can you get nylon bass strings??

peach_fart (author)mdog932010-12-12

yes it was a steel string, i dont know about nylon bass strings, and the action is probably high due to neck warping. im guessing he welded the hinge to use as the tailpiece.

mdog93 (author)peach_fart2010-12-13

yes, the strings will also be too loose when tuned to a bass tuning because he didn't lengthen the scale length to that of a bass guitar. The only way to make this technically a proper bass would be to move the bridge further back, if it would fit on the guitar still at the correct length, but then you'd either have to extend the neck and remove the frets fill the old slots and reposition them so the 12th fret is halfway between the nut and bridge OR remove the frets fill in and prepare new neck then refret the frets in the correct position, but this would mean you would have less frets overall

peach_fart (author)mdog932010-12-13

it could still be played like a bass at that scale but you would probably be forced to used a low tuning such as b standard

mdog93 (author)peach_fart2010-12-14

well i don't deal with that, i only play standard EADG tuning. although if you are willing to put quite a bit more effort in it might be possible to turn an acoustic guitar into a proper acoustic bass by doing the things i said above, you just have to put a lot of time and effort into hiding the old marks and snagind it down and refinishing it to make it look nice.

I'd like to try doing it but its hard to find time these days and i don't have a spare steel string acoustic guitar and unless i ever find one cheap or acquire one i'm not about to buy one just to do that to it.

Pryo Chain (author)mdog932011-03-22

...or you could buy a bass and not waste a perfectly good acoustic...

mdog93 (author)Pryo Chain2011-03-26

sorry, you seem to misunderstand part of the magic of instructables. Let me explain for you:

*Some things are cheaply made, and designed so are not very good at their job so people might modify or improve them- bringing me onto my next point
*If somethin is old, useless, unwanted, been thrown away by somebody else it can be RE-USED, or UP-CYCLED
*Another thing is saving money- some things are cheaper to make from scratch or by modifying or up-cycling something cheaper than buying one from a shop.
This is also better if somebody only wants the item for satisfactory use, ie.e they are not a bassist but would like to have an acoustic bass to play with and mess around but because they are not an expert they do not want to fork out £500+ for one and also if they did buy one they wouldn't be able to do it justice anyway and if they made one it would not matter if it got a little damaged.

Whilst i do not think this instructable is erfect as structurally i would be dubious about doing this without reinforcing the neck. However i would imagine many people would like this and make one, just because you wouldn't want to doesn't mean others can't. If you can't make any constructive criticism, please don't be destructive of what other people are passionate about and have spent their own time documenting for other people.

Want me to carry on?

ComplacentBard (author)2011-02-28

It seems like the scale length would be very short for a bass and that the strings would have to be very loose.

Very ambitous, though

toakhong (author)2010-12-01

Nice! I might try this after i get a replacement for my old acoustic.

Just one question. If you use an electrc-acoustic guitar for this, how would it sound when plugged in?

iamtoats (author)toakhong2010-12-04

The same way you always did, through the piezo.

peach_fart (author)iamtoats2010-12-12

i think he meant would the sound drop off because the pre-amp was meant for guitar frequencies or if it would play the lower notes fine

blindsagacity (author)2010-12-02

Hey, one the you could do to improve the intonation (though it would require a bit of work) is to move the saddle closer to the tailpiece to compensate for the effect that thicker strings have on intonation

kyrisroy (author)2010-11-30

Cool, I have an old acoustic and this sounds like an awesome idea.

Houdinipeter (author)2010-11-27

Great Instructable!

Oh and does the guitar have a truss rod? Cuz if not the bass strings might have to much tension on the neck... But let us know how it turns out after a few months!

gmoon (author)2010-11-25

It seems somewhat unlikely that the bracing on a normal acoustic will be sufficient for bass strings--at least in standard tuning.

You could add more bracing to the top. That would require some major surgery, though.

I wish you luck with it, I hope it holds up to use. Maybe tune it down a half step or two...

I'm not sure how old that "Kay" guitar is, but if it has a solid wood back, top and sides, it was probably worth restoring as a regular guitar. Your choice, of course. It's probably not worth a ton of cash, either way...

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