Things You'll Need
- Allen wrench
- Small graduated scale
Whenever you change the gauge or type of strings you use, you may have to adjust the neck of an acoustic guitar. The truss rod is used to counteract the tension of the strings on Martin acoustics. It is adjustable in either direction and can drastically change the way a guitar plays. With a little experience, you can adjust the relief on a Martin acoustic guitar. Just be careful to not overdo it and damage the neck.
Strum the guitar, playing notes on the high and low frets. If you hear fret buzz, you may want to adjust the neck relief using the truss rod. More buzz on the higher frets than the lower frets means that your neck may be too straight, and vice-versa if the buzz is more noticeable on the lower frets.
Check the current relief of the neck of your Martin acoustic guitar. Press down on the first fret and the 14th fret with your other hand. Do this in the playing position or with the guitar on a table or workbench. This will allow you to see the gap between the string and the fret at the sixth fret. If the gap is more than 0.013", you may have to adjust the neck forward to decrease it, and too small of a gap will require the opposite adjustment.
Reach your hand in the sound hole to feel for the truss rod adjustment hole. It will be at the end of the neck through the upper brace for the hollow body. Alternatively, tilt the guitar forward and look for the hole, it will be relatively close to the end of the sound hole on the neck side.
Slide a 5-mm Allen wrench into the hole, feeling for the truss rod adjustment nut. Slide the end into the nut and prepare to turn the wrench to make the proper adjustment. Slide it in all the way to prevent slippage, which could damage the guitar.
Turn the Allen wrench about a quarter turn in the appropriate direction to adjust the neck. Turning the truss rod clockwise on a Martin acoustic will straighten the neck, and turning it counterclockwise will have the opposite effect, creating more relief, which may make the guitar more difficult to play due to the larger gap this action will create. Make small adjustments until you are happy with the results.
Christian Mullen is a graduate from the University of Central Florida with a bachelor's degree in finance. He has written content articles online since 2009, specializing in financial topics. A professional musician, Mullen also has expert knowledge of the music industry and all of its facets.