Heresy: Guitar Construction by Dixie

 

With regards to building a better sounding guitar, I've lately taken to building guitars with two distinctly different new ideas. One....that a steel rod is solidly attached to the heel of the neck, and this rod continues all the way through the body of the guitar to solidly attach to the end block. This arrangement takes all of the usual strain exerted by string tension away from trying to distort the body of the guitar. The guitar body can then be braced lighter, especially in the upper bout.

The second innovation is the manner in which the top is braced: very stiff in the center beneath the bridge, but very flexible where the top joins the side.

Guitars manufactured by Gibson and Martin in the 1930's have become our standard of excellence for sound quality. Much of what is done today is to slavishly copy each small detail of these old guitars to hopefully achieve this quality of sound. The highest end of the acoustic market today does exactly that. This trend makes the assumption that these manufacturers were wise and all knowing in the deep mysteries of guitar design: no other improvement is either wanted or necessary. Some of these old guitars were indeed spectacular in their sound department but were not all equally great. The Martin Company invented the X bracing system for bracing their gut string guitars. At the time the European classical guitar makers were already way ahead of Martin in the way of sound, with the fan bracing system. The Spanish classical guitarmakers (and at least one noteworthy German maker) worked out a good sounding arrangement for gut string guitars at least a hundred years ago. Their design was improved year after year, achieving better and better sound. In the world of classical guitars, all professionals >use only new guitars--the old ones are not up to the task. Steel string guitar makers could do well to pay more attention to what modern classical makers are doing.

Right around 1929 when both Martin and Gibson were getting into the steel string flat-top business, Gibson copied Martin X bracing system for their flat-top design. This bracing system uses very few but relatively massive braces to keep the guitar top from distorting (caving in) from the stress that steel strings put on the soundboard. Using very few braces saves time and effort in the manufacturing process. The Martin X brace system makes use of the top itself as the main bracing material. The top piece of wood (spruce) has a very stiff resistance to bending, provided care is taken to cut that piece of wood so that the grain lines are vertical to the top plane of the guitar top. The top itself is left fairly thick. Since no two pieces of wood are equal in this respect, some guitars turn out much better than others. Such is the case with old Martins and Gibsons. Some are indeed wonderful sounding instruments; some are not so great. What can be done to make sound quality more consistent? Use a very thin top and more bracing.

It would be ideal if 100% of the string energy could be used to drive the guitar's bridge; the bridge would then drive the top much like a speaker in an amp. Unfortunately, much of that energy is absorbed in the guitar's neck and the necessary heavy bracing in the upper bout. The neck should therefore be made as rigid as is practically possible. A solid (non adjustable) truss rod of a large size is best for this purpose. The rod through the guitar's body continues this rigidity.


Guitars built in such a way are unique in that they will never need any further adjustments....forever. String tension is a constant force to be dealt with in keeping an acoustical guitar in decent playing condition, It is common for guitars to need timely adjustments such as lowering of the bridge saddle and maybe even a neck set. String tension is constantly trying to bend the neck and also the body itself. This simple idea will put an end to this need.


The next bracing system, show above, is made specifically for guitars using a tailpiece to anchor the strings, with a floating bridge. Notice that directly under the bridge is a built-up truss. This is built of laminated carbon fiber and balsa wood. The idea here is to make the area directly under the bridge very stiff, but with very little mass.

There is part of the neck protruding into the body, all the way to the soundhole. This effectively stops all vibration in the upper bout. What we want here is to put the most string vibration directly to the bridge. Making the neck itself extra stiff is also part of the idea. The neck uses a non-adjustable 1/2 x 1/2 inch square steel tube for a trussrod. Making the neck from a dense hardwood also helps.


Of course all guitar makers claim that their product sounds better than most and bla, bla, bla. We all all know that hearing is believing.