Lights, Camera…ACTION

I’ve been reading a lot about playability of guitars, guitar set-up, and adjusting your own guitar. After a trip to Guitar Center this weekend, and listening to the floor people talk about adjusting the truss rod to bring down the action…again…I’ve decided to clear the air.

Playability and action on a guitar are specific to the player. I have a friend who plays bluegrass, that not withstanding I still count him as a friend. The point is all of his guitars are set with high action. For me, that makes his guitars un-playable… as for him, he wouldn’t have it any other way. I guess one person’s trash IS another person’s treasure. My playing style is pretty light, so I can have very low action on my guitars.

There are four aspects of the guitar that have an influence on the action: relief, neck angle, saddle and nut height. All are adjusted so that the guitar can be played easily, without buzzing, and in tune. Each can be adjusted to compensate for another that is not set correctly, however to maximize the potential of each guitar, all three have to live in synchronicity.

Relief: The neck of the guitar is designed so that when the strings vibrate, the neck makes room by dropping away making room for the string to vibrate freely. The curve of the neck should mimic the arc that is created when the string vibrates. If there is too much relief in the neck, the neck will have too much bow, therefore making the string height (action) high. High action causes a few things to happen. First it makes playing a little more difficult, and it can also cause the guitars intonation to be out of whack. Adjusting the relief in a neck is as easy as righty tighty, lefty loosey. I posted about the proper care and truss rod adjustment here. The neck should have a gentle curve when the guitar is up to tune. Sometimes you can put a ruler on it, for me, I have to just look, play, adjust, and repeat.

Neck Angle: This is probably the least understood, but most critical part of the guitar set-up. if your neck is on wrong, all the adjustments in the world will not help. This is something that is done at the factory for the most part. On electric guitars with bolt on necks, the neck pocket (on the body) is routed so that the surface that connects to the neck is not parallel to the top (of the guitar), but pitched back slightly, only 2 or 3 degrees. If you have a floating tremolo or an LP style set-up, your neck angle will have to be a little more pitch to it, if you have a vintage style bridge, less.

It’s kinda like Goldilocks and the Three Bears. You can have too much angle, not enough angle, or it can be just right. To check, sight down the bass edge of the fingerboard (not the fret surface) focusing on the end of the board too the bridge. If you complete the line off the end of your fingerboard to the saddle, the imaginary line should end about midway up the low E saddle. If your angle is too much, the end of your fingerboard will peak and the string will buzz or in extreme cases fret out. Too little angle and your action will be high, and no amount of truss rod adjustment of saddle tweaking will bring in into compliance.

On acoustic guitars the neck angle can be compromised by the top. For the most part, Acoustic necks are set, but the top can either puff up or sink, changing the neck angle, and making playability a little sketchy.

Again it is somewhat easy to tweak the neck angle using a shim, but you need to be careful. If you do not shim correctly, you can literally create a hump or irregular plane in the higher frets. For neck thru models and most all acoustic guitars, neck angle adjustment becomes a complicated matter, and should be addressed by a professional.

Exceptions: There is a case where having a negative neck angle is acceptable. In some Classical guitars, the neck is actually set so that the strings leave the bridge and travel upward with respect to the guitar top. You can see an example here.

Saddle Height: The saddle height is the one aspect where you can have a direct influence on the height of the strings. If you have individual saddles, start by adjusting them about a fret height over the fret liner of your fingerboard. (See above sighting down the neck)

My rule of thumb is: Using the fret as a measuring unit, the top of the saddle should be a fret above the plane of the frets on the fingerboard. If you play harder, you will need to raise the string height. If you play light, you may need to do nothing at all. this is a good place to start, and any fine tuning can be made from this point.

Individual saddles should be set to mimic the curve of the fret board, and this can be done by eye. Setting the final height should be done by ear. If you play, and the strings buzz, raise the saddle a little, if you have to raise the string a great deal to eliminate buzzing, check the neck relief.

Nut Height: The nut should act as a zero fret/string guide. With a nut that is cut too high, the strings height is up at the low end making fretting difficult, and causing intonation problems. Too low, and you get low fret buzz and fret outs. You can check to see if your nut is cut properly by fretting the strings at the 2nd or 3rd fret and looking at the space between the bottom of the string and the top of the 1st fret. the string should have a viewable a disgernable gap, but not too much. again it’s something that I see rather than measure.

Tying it all up: Action is a balancing act that takes all three aspects into consideration. If you have set the proper relief, neck angle and saddle and nut height, your guitar will play well for you specifically.