Acoustic Guitar Setup





Introduction: Acoustic Guitar Setup

Thanks to cheap labor and mass manufacturing in China, there is a surprisingly wide variety of acoustic guitars available for around $100. So what separates these cheap guitars from those costing five or ten times as much? Modern manufacturing can maintain a relatively high build quality, so the extra money mainly goes towards using rare woods and the additional hand labor for precise set-up. It is my opinion that inexpensive guitars sound fine but can be a little awkward to play . With a little time and care though, it is possible to setup one of these inexpensive guitars with the playability of one costing ten times as much. Here are the adjustments that usually need to be made.

Step 1: Adjust the Truss Rod

The truss rod is used to provide counter tension against the strings to keep the neck in the proper position. It is not used for adjusting the action, this is done in later steps at the nut and bridge. The head of the truss rod is accessed at the top of the neck or from within the sound hole depending on the guitar.

To check the tension on the neck, first make sure the guitar is properly tuned. Then place a capo on the first fret and press down the first string at the 14th fret. Now check the clearance at the 6th fret. You should be able to just fit a piece of heavy card stock (index or business card) under the string at the 6th fret. Tighten the truss rod to decrease the clearance. Loosen the truss rod to increase the clearance

The diagram was found at:

Step 2: Check the Neck Angle

Most setup guides that I have referenced seem to skip over this crucial step. Ideally the neck should be mounted onto the guitar body with a very slight angle; with no tension in the strings and the guitar laying on its back, the neck should be angled slightly downward so that the top of the fretboard is on the same plane as the guitar body. With a straight edge against the body of the guitar, the neck should decline until the top of the fretboard is inline with the straight edge right before the nut.

Step 3: Check the Neck Angle

Here is the neck angle on a $80 guitar I picked up recently. It does have a slight angle, but in the wrong direction

Step 4: Correcting the Neck Angle

With the proper neck angle, the plane of the fretboard should intersect the top of the bridge. This can also be confirmed with a straightedge.  The image shows an example of how a poor neck angle affects the alignment with the bridge.

***I should confess that I didn't decide to put together the instructable until the project was underway.  The image shows the bridge after I had already started sanding it (which is no secret from the way it looks).  Originally it was even higher.

Step 5: Correcting the Neck Angle

Unfortunately the neck angle is fixed when the neck is mounted to the body and cannot be adjusted unless it is detached and reseated. Of the inexpensive guitars I have evaluated, this specification seems to be most variable. One solution may be to sneak a straight edge into the music store and inspect the guitar before purchasing. But if your goal is to save a few dollars you’ll probably be shopping online for the best deal and will be unable to inspect it before buying.

Since we can’t easily change the plane of the neck, the only option is to adjust the bridge. I sanded off about 1/8 of an inch to get the bridge inline with the fretboard.

Since the thickness of the bridge can affect the sound of the guitar, I decided to cut a few string grooves behind the saddle to minimize the amount I lowered the entire surface.

***I've had a few questions about why it is necessary to lower the bridge in addition to lowering the saddle.  Here is an answer I posted:

When you look at the saddle you see that the strings go over the saddle and then attach at the back of the bridge.  The saddle needs to rise above the bridge so that the strings angle down to their attachment point on the bridge.  By angling downwards from the bridge, the strings apply enough force to press the saddle firmly onto the bridge.  The job of the saddle is to transmit the vibrations to the bridge, which distributes the vibrations over the guitar body.  If I just sanded down the saddle without lowering the plane of the bridge then the strings would no longer anger downward to their attachment point; the saddle would not receive enough force [by the strings] to stay in place and start to buzz when it vibrates.  Even after I sanded down the bridge I still found it necessary to cut a few grooves behind the saddle in order to further increase the angle of the strings.  This assured that the strings would exert enough downward force on the saddle to keep it firmly in place.

The other reason (maybe more obvious) is that if the neck is misaligned you could shave the saddle all the way down to the groove it sits in and still not have the action low enough.  In the case with the guitar pictured, I ended up sanding down the saddle to a point below the original plane of the bridge.  If I didn't sand down the bridge the saddle wouldn't have even risen out of the groove!

Step 6: Adjusting the Nut

After fixing any problems with the truss rod or neck angle you can start adjusting the action at the nut. This is done by pressing each string down after the second fret and checking the clearance above the first. The clearance should be adjusted to the thickness of an index card:

Step 7: Adjusting the Nut

Reduce the clearance by carefully filing down the string grooves with a thin needle file:

Step 8: Adjusting the Nut

Once the nut is adjusted I recommend lubricating the grooves with a teflon based machine oil. This will prevent the strings from burrowing down further into the nut as they are tuned. It also prevents burrs from forming and catching against the string, causing it to break when tuning the guitar.

Step 9: Adjusting the Saddle

The height of the saddle is the main component in determining the action. Only begin adusting the action at the saddle after you have completed all of the other steps. It is adjusted by removing material with sandpaper and a sanding block.

The top should be slightly contoured to allow the thinnest strings to sit a little lower. The overall action varies based on preference but a clearance of 3/16” above the 12th fret is a typical rule of thumb. I recommend buying a few acoustic guitar saddles (I found them online for $1.50 each) to allow the freedom to experiment and find the best setup.

Step 10: Finishing Up

If you change the gauge of your strings you should double check the truss rod and bridge. Thicker strings will produce more tension and will need a bit more force to counter it. Also, they require greater force against the fretboard so you may want to lower the action at the saddle to compensate. If you plan to try a new string gauge then you should plan on ordering a new saddle also.

Going through these steps may take some time but it will be worth the effort. Now that you know what to look for, the next time you walk through a guitar shop check these parameters on a few guitars and you will be surprised at how variable the factory setup can be. It will put a smile on your face when you compare the playability of your properly adjusted $80 guitar to some costing several hundreds of dollars but still in need of a little work.
The image shows the final result with the saddle mounted and a fresh coat of varnish over the bridge.


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By lowering the bridge height it becomes possible to lower the saddle height some more...However, this will also cause problems with the sting windings climbing onto the saddle, and ruining the intonation of the instrument and tone...not that this is much of a concern on an $80 instrument, which probably has a plywood top and sides...this is a good fix for this situation though...

What's the point of this step?  Doesn't the height of the saddle determine the height of the strings?  If you aren't routing out a deeper channel for the saddle to sit in, how does this affect string height?  I'm confused.


You're not confused, you're right. This is a simplistic at best tutorial.

Thanks for the feedback.  I had another question about this so I decided to include the explanation in the text for step 5.

Err, what you don't mention is that sanding down the bridge is likely to negatively affect the sound of the guitar, ie it will lose bass and power. It's best to leave the bridge alone and work with adjusting the saddle height. The other thing that's important to be aware of is that on many guitars the neck tilts backwards in relation to the body, particularly on Gibsons.

If the neck angle really is an issue, ie when the saddle ends up too high or too low, and the guitar is valuable enough, the best thing is to take it to a good luthier and have the neck reset. This means taking it off and putting it back on at a slightly different angle and is a specialist job.

A neck reset is often done on older guitars where the pull of the strings over time gradually tilts the neck forwards. Tell-tale signs are the saddle needing to be set lower and lower over the years and the sound losing its high end. A neck reset will give the sound of an old guitar back its life and sparkle.

Thanks for this instructable, it's brilliant, and I kep it bookmarked for a reference now. :)

Do you have any ideas for loose keys? I've got one of those famous cheap guitars where the string loosens as soon as I tighten it, and I'm wondering if it's worth trying to fix up. (Or using as a practice piece for modifications. :D)

Thanks for this. I agree; the neck angle is never mentioned,perhaps because it can be a problem to remedy. Sighting down the neck toward the bridge can give you a pretty good indication of the amount of work needed. Steve

great ible! but man why do you use a cheater(capo)?

 Awesome Instructable.  Excellent detail!

Another thing I have done with the cheap chinese instruments is to sand down the frets and (sometimes file!) fretboard or inlay.  As the price comes down the finish suffers, but the sound can be OK.  Often the mother of pearl inlay is proud of the wood on the fretboard along with glue drips or crummy paint on the fretboard. I usually use a mix of half linseed oil / half turps to rub on it afterwards.

Keep up the good work!