More CC vs RC questions was RE: Killer Octave & Pitch Raise

[Sarah Fox]

Hi Terry,

> I don't know how the numbers would actually work out in
> a working soundboard, but perhaps its not inconceivable that a CC board
> could end up with similar stiffness as a RC&S board - by varying panel
> thickness or whatever - maybe it's just that stiffness is achieved in part
> by different means (and that may only be a small percentage of total
> stiffness).
>
> If what I am suggesting holds any water at all, it may be then that the 
> two
> systems might not necessarily produce greatly divergent tonal qualities.

I'm just speculating, like the rest of y'all, but...

I don't think total stiffness is the whole story.  With a CC board, the 
stiffness is a function of cross-grain compression, and the elasticity is 
with respect to a directionality of compression for which the tree (that 
grew the wood) was ill equipped -- a crushing force from the side.  The 
tension, on the other hand (and there must be tension to oppose the 
compression) is in the ribs and runs longitudinally with the grain (the way 
the tree was built to handle it).  There is also some tension/compression in 
the rim, in the direction of the grain.  In all this mess, there is a mix of 
very elastic elements (longitudinally tensioned/compressed fibers) and less 
elastic elements (transversely compressed fibers).  Those less elastic 
elements are going to "modify" vibrations in the entire structure by 
"soaking up" (or more accurately dissipating) vibrational energy.  How will 
the vibrations be "modified?"  I don't know exactly.  My guess is that there 
is hysteresis that would dissipate higher frequencies much faster than lower 
frequencies, resulting in a "mellowing" of the tone.

In a RC/S board, tension/compression runs completely in the direction the 
Great Goddess intended -- longitudinally.  Trees were designed to be very 
sturdy and elastic in that direction.  Vibration will not be damped so much 
by hysteresis in the system, although there will still be *some* hysteresis. 
I would think a RC/S board, therefore, would tend to be more "brilliant" or 
"bright."

Of course  there's another very important factor in all this mix: voicing. 
Side by side, CC and RC/S pianos are going to be voiced by the same 
technician to have the same tonal outcome in mind.  I suspect a CC piano's 
hammers are going to be inherently brighter than a RC/S piano's in order to 
achieve a similar tone.  However, I also suspect the upper partials on a 
note played on a RC/S piano will sustain longer, retaining more of the the 
"brightness" of the sound throughout the note's duration.  So while the 
sound may be similar on attack, it may differ on sustain.  The difference 
may be very subtle.  Perhaps all things being equal, the sustain in the high 
treble of a RC/S piano will also be inherently longer, due to less 
hysteresis in the system.

If all this is true, a CC and RC/S piano may have somewhat different flavors 
in performance.  A CC piano may feel/sound slightly brighter during faster 
passages and darker during slower passages, with melody delineated more 
clearly from accompaniment.  A RC/S piano might be more uniform and overall 
better suited for more "brilliant" works (acoustically brilliant, that is).

Of course this is all just arm chair speculation on my part.  Does any of 
this jibe with what y'all have experienced in the field?

Personally, I'm a big fan of the expressiveness of the American Golden Age 
pianos, and perhaps some of the expressiveness in these pianos derives from 
the inefficiencies of the CC board.  On the other hand, it's hard to argue 
against the longevity, stability, and treble response properties of an RC/S 
board.  It's equally hard to argue against the smooth, brooding qualities of 
one of Ron Overs' beautiful pianos!  It would be very interesting if someone 
were to experiment with a hybrid board, combining the properties of CC and 
RC/S.  (Would that even be possible? Perhaps RC/S in the treble end and CC 
elsewhere?  Perhaps a split board, joined at the rib???)  Or how about a 
different sort of board entirely?  How about a violin-like board that has 
its crown milled/sculpted into the wood like a very shallow bowl, lightly 
supported/stabilized with smaller, shaped ribs?  How about a RC/S board with 
an electromagnetic low-pass damping device that would slowly dissipate 
higher partials?  So many fun possibilities!  Fascinating stuff!  :-)

Peace,
Sarah