Soundboard stiffness vs. string coupling

[V T]

Hello List,

I have been reading the discussion about soundboard
crown with great interest and feel compelled to add a
possibly relevant observation.

I am starting with the assumption that one intended
benefit of the downbearing force is the increase in
board stiffness.  It's pretty obvious that the
downbearing of a single string isn't significant to
accomplish much change in stiffness.  The increase in
stiffness is the result of the composite force exerted
by all the strings (however that force is
distributed).

There is however another design parameter that
matters;  that is the amount of downward pressure from
a single string.  This factor is important, because it
determines the coupling of the individual resonator
(string) to the bridge/board.  This coupling parameter
is a separate issue from board stiffness.

So, we have the following problem:  we have to adjust
two parameters (board stiffness and string coupling),
but we do it by adjusting one variable - downbearing
force.  What if the downbearing required to get the
right board stiffness isn't the same downbearing that
results in the best coupling from an individual string
to the board?

That, I believe, is a significant problem in the art
of the soundboard design.  One way to separate the two
design parameters is to build a soundboard that either
doesn't need downbearing in order to achieve the right
stiffness, or perhaps a board that has an alternate
means of adjusting the stiffness.  Then, it would be
possible to adjust the downbearing of each string just
for the purpose of tweaking the coupling of the string
to the board.

Optimizing two parameters with one adjustment can be
tough.

What do you all think?

Vladan



		
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