Practical results of depth adjustment

[Dave Bagwill]

What is gained/lost by increasing or decreasing the body depth of a given guitar shape - say an OM?

And the reasoning behind the taper on the sides?

[Tim Benware]

You'll probably get a number of responses on this one. Mine- a little added volume and bass.

[ken cierp]

I believe the taper -- deeper at the tail block is a matter of player comfort. There have been guitars made with the opposite configuration and it is my understanding they sound as good as the more common design. For the logic regarding size -- I look to the violin (violin, cello, viola, upright bass etc.) and drum families of instruments depth and size (interior air volume) having a huge impact on bass responce and output volume -- sorry not very scientific. Any guitar can be adjusted to a certain degree by using lighter or heavier string gauges and also the size of the sound hole can be made larger or smaller. Interestingly a Charles Fox video mentions that his adjustable sound port does little!!!

[TonyinNYC]

Dave,
Increasing the volume of the box lets the guitar produce more bass and more volume in general. Decreasing the size would do the opposite.

When you speak of the taper, are you talking about how the sides are shaped on the blueprints for a guitar?

[Robert Hosmer]

For adjustment of depth:
I'll side with the most common response- adjustment of chamber volume.
If time and resources permitted, one could build models of altered dimensions from identical materials to prove a point. The problem is that the materials used to establish results are not truly "identical", and there are many other variables that could affect the outcome. So enter the "what- ifs" and "buts" and "howevers".
But much has been done by those before us, and the most common designs are time-tested and at least establish generalities.

Why would one deviate from already-established dimensions?
I'm gonna go out on a limb and state that quite often it's a case of one desiring results comparable to a baseline model, but available material may determine a slightly different route to get there.

Some of my ponderings:
"I want the sound characteristics of a dread size, but my plates only allow width of OM, and I don't want to do a 3-piece back. But my side material is wide enough to make the box deeper. What is the effect of a deep OM?"
Or conversely, "I want the sound characteristics of an OM, but the only suitable side material I have that's long enough is too narrow for the plans. But my plate material is plenty wide to go larger. What would be the effect of a shallow dread?"

Both situations use an altered way of obtaining a targeted chamber volume.
Unless I find an experienced, reliable source who has already constructed a "deep OM" or "shallow dread", the only way to really find out is to build them myself. Even then, there are so many other variables involved, it may be difficult to conclude anything unless successive builds were done.


Rob

[ken cierp]

I too like the idea of using a known model to get specific results -- while I am opposed to cloning from an artistic stand-point, using the base dims, woods, scale etc. is a good path to getting an instrument that, long term (aging is a real element) will sound similar to a guitar you like.

The idea of the effect of interior volume can be tested and explored by going to a Martin dealer and examining the "000" (OM 14th fret) and the "0000" which is a larger version (same shape) offered in the deep and thin body styles -- J deep, M thin.