The only right way to make a “high string action” Martin guitar play correctly is to do a “neck set”. This repair involves removing the neck on the guitar, and refitting the neck at a slightly increased angle, which lowers the string action. If done correctly, this does not affect the value of the guitar (and in fact can make it more valuable, as the guitar is much more playable). Generally speaking, most players would agree if the “string action” is more than 3/16 inch (5 mm) at the 12th fret, the guitar needs a neck set. This measurement is taken from the bottom of the low-E string, to the top of the 12th fret.
This is a somewhat expensive and delicate repair. But it is a repair often needed on many vintage Martins. A proper neck set not only makes the guitar play better, but also will make it *sound* better too.
Because a neck set is expensive, some owners/repair people will take “short cuts” to avoid doing a neck set. These short cuts are usually temporary at best, and never give the best outcome. These include lowering the bridge saddle and lowering the bridge.
Lowering the Saddle.
The original saddle is desirable on a vintage Martin. So when lowering the saddle, remove the original saddle (and store is safely away), and have a new lower saddle installed (removing material from the saddle is to lower it, so don’t mess with the original saddle). The problem with lowering a saddle is this: the lower the saddle, the less “drive” there is across the bridge and the top of the guitar. The less “drive”, and the guitar won’t usually sound as good as it could.
Remember, on a flat top guitar the strings “drive” the bridge, which vibrates the top of the guitar. This is where the sound and tone come from. The lower the bridge saddle, the less “drive”, and the less potential tone. The ideal bridge saddle height should be about 1/8″ to 3/16″ (4 to 5 mm) above the top surface of the bridge.
Lowering the Bridge (yikes!)
Again, as with the bridge saddle, too low of a bridge will decrease the “drive” of the strings. Thus the sound and tone will suffer. Also a low bridge is structurally not a good idea, as the bridge can more easily crack (and damage the top of the guitar). Most original Martin guitar bridges are about 3/8″ tall (from bottom to the highest part of the bridge).
After lowering the bridge (usually in a failed attempt at getting lower string action), the owner will eventually realize this is not the best solution. When this happens and a neck reset is preformed, the original bridge will now be *useless* (because it is too low!) The repair guy won’t reset the neck to a low bridge, so a new replacement bridge will be installed. At this point the originality of the instrument is compromised.
Learn to play guitar
Again, if a Martin guitar needs a neck set, don’t try and solve the problem of high string action any other way! Take the guitar to a *good* repair person, pay the money, and have a proper neck set done. A good neck set will make the guitar play and sound the best it can. With the correct neck set and bridge and saddle height, the guitar strings will drive the top of the guitar best, giving the best sound possible, and at the ideal playing action. And after all, isn’t that what it’s all about?