Questions: String Compensation

by Mike Doolin

Originally published in American Lutherie #69, 2002 and Big Red Book of American Lutherie Volume Six, 2013



Brett from cyberspace asks:

I had always been of the opinion that saddle compensation was to overcome the tendency of a thicker string to be less amenable to vibrate than a thin one. So a high E will be vibrating close to the saddle, and a low E, being stiffer, will start vibrating a bit further away, hence compensation.

That idea gave me peace for a while because I really couldn’t see the tiny distance a string gets pushed down to the fret as making any significant difference. The kicker, though, is that if I believe that theory, the string isn’t vibrating at all where it touches the saddle. If that’s the case, how does the vibration actually travel to the body and neck? If I follow my logic further, I’ve got to concede that the vibration is a type of compressive function in which the string compresses the axe as it gets to the widest part of its travel, lets it off as it passes through the resting point, and compresses it again as it zooms out to the widest point of its vibration on the other side, with maybe a slight forward bending of the guitar at the tightest points of the vibration (because the string isn’t lying flat on the fretboard). If a vibrating string’s tension isn’t constant, won’t a strongly-picked string tend to be sharp? Further, won’t it tend to go sharp-flat-sharp as it vibrates in decreasing cycles as it runs out of energy? It’s nano stuff I know, but I’ve always wondered.