Killer Octave & Pitch Raise

[Richard Brekne]

Hi David

At the risk of reviving a discussion held here some years back with one 
Frank Weston, I would point out that there is little tension anywhere in 
the soundboard CC assembly.  If you meant by "tension",  the more 
general  "stress" then I understand your question below, and indeed it 
is exactly these kinds of questions I still find a satisfactory answer 
in lacking.

One gets quickly into the discussion of just what vibrational activities 
are involved in causeing the exact transverse vibrations from the 
soundboard that sets the air in motion.  If one takes the view that it 
is only the particular combination of stiffness and mass on the part of 
the soundboard that governs this output... then one quickly would be 
forced to conclude that the RC board is preferable due to its ease of 
construction and predictablity visa vi the CC board. 

However.... I have difficulty accepting without further ado, the a panel 
which is under large compression and otherwise has identical stiffness 
to mass relationships as another panel without said compression (if that 
equality is even possible to begin with)  will perform equally or even 
nearly so from an acoustical output point of view.  Of course my 
difficulty in accepting this does not mean that it is not so... but if 
it is then there must be a fairly easy to follow rational / explanation 
for why it is so... and so far I have yet to hear one. 

None of this btw is meant to infere the superiorty one way or the other 
of one type of board over the other. Its only meant to point out that 
the different methods most likely do indeed result in differing 
acoustics.  Which of these any particiular person finds preferable is an 
entirely different subject.. yes ??

Cheers
RicB



I have a related question about downbearing.  It would seem that a CC
board prior to the application of string bearing is already under a
certain amount of tension due to the crowning process as compared to a
RC board.  That being the case, and if a certain amount of
tension/stiffness is a goal common to both types, might it not be the
case that the amount of bearing required in a RC board would be greater
than in a CC board to achieve the same tonal output.  
 
David Love