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.

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.


http://www.taylorguitars.com/global/pdfs/truss_rod_adjustment.pdf

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.




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.

This is what a correct neck angle should look lke:



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



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. 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.

This is how a poor neck angle affects the alignment with the bridge:



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 thickness of the bridge can affect the sound of the guitar, I decided to cut a few string grooves at the rear of the bridge as apposed to lowering the entire surface, as seen in the picture.

The bridge is lowered to the plane of the fretboard:



3) 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:



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



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 prevent burrs from forming and catching against the string, causing it to brake when tuning the guitar.



4) 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.

The final action:


Here is a look at the finished bridge and saddle after a fresh coat of varnish:


**One note: 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 a little work.