Is a stiff top better?

[Herman]

Here is a paper of a German making a mathematic approach to state that the search for the stiffest tops is questionable.
Herman

http://www.germanspruce.com/downloads/m ... nn_coq.pdf

[ken cierp]

OMG -- I am back in the class room --- someone get the barf bag!

a machine to test yes -- a panel of human ears to test yes

an equation to test --- what would Wayne Henderson say?

Sorry for me, just not my thing.

[John Parchem]

The paper is basically saying that density and the Young's Modulus or E-Modulus provide the greatest criteria when evaluating top wood for sound. They go farther to say that the tone wood people should provide this measurable information as part of their grading. I do not mind the equations or what the paper is saying. I suspect the tone wood vendors will not want to play.

I do these tests for every plate I am going to use. There is not an equation that defines a good guitar sound but using the characteristics of the wood one can achieve better consistency of sound guitar to guitar. There are equations as defined in this paper that allow one to normalize the plates to achieve consistent resonance frequencies. (This is assumes consistency in bracing as well.)

Just as an example take a very stiff but dense plate and a less stiff but less dense plate. One can thin the stiff plate more than the less stiff plate to achieve ones target stiffness. It may turn out that the denser finished plate has less mass or the other way around depending on the relative stiffness/mass for the 2 plates.

The equations I use from the Gore\Gilet books allow me to calculate a target thickness for each plate. I still control the sound as there is a user settable constant in the equation. The equation uses both the density and the Young's modulus of the wood to determine the thickness.

I have learned a few methods without equations. Kent Everett shakes the tops as he is thinning until it sounds like sheet medal. Rick Davis taught me to thin the plate until it has a great tap sound and then thin it more until the sound gets more chaotic. Some flex the plate un-braced and the braced top until it feels right. All of these methods rely on the stiffness of the wood and its density. Depending on the sensitivity of the tester they can achieve consistent results.

[Herman]

Ken, gotcha! I knew you would bite. ;-)
For your relief: I prefer to use my senses when shaping tops.
Herman