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

[Ron Nossaman]

>I see, so therefore a lower spring rate will result in the board moving
>more easily and therefore a softer hammer would be needed to control
>attack levels?

The softer hammer is demonstrably necessary, and I presume the lower spring 
rate is the reason.


>So if that's true and if the firmness of the hammer
>regulates the balance of partials, say, does it follow that there is a
>point where a lower spring rate might result in the requirement of too
>soft a hammer to create the desired balance of partials while still
>keeping the attack levels under control?

Yes. Spring rate would be the stiffness component of mechanical impedance, 
and too low a spring rate would equate to not enough stiffness and you 
would have the functional equivalent of a killer octave. This stuff all 
ties together somewhere in there.


>A noticeable thing about most
>of the CC boards that I come across is that they not only tolerate, but
>seem to require a firmer hammer yet when they work they create a nice
>partial balance.  I would tend to hypothesize, then, that equivalence
>between soundboard assemblies (in terms of balance between tonal attack
>and partial balance) has everything to do with spring rate.

Or at least a whole lot.


>How do most
>CC boards compare with RC&S boards in terms of spring rate?

The progressive spring rate of CC boards will be a much steeper gradient 
than that of an RC&S board, so slight changes in bearing should have a 
greater effect on CC boards. From my experience, this seems to be the case. 
With the progressive spring rate coming from panel compression, the 
impedance of the assembly is more likely to change, and to change more 
radically with humidity swings, and with cumulative panel compression set 
in the CC board. This also seems to be the case.


>I have noticed since this discussion started and I am paying attention
>to these things more acutely, that the difference between pianos has
>mostly to do with the sound at attack, how the tone develops over time
>and the balance of partials.  It seems that these should be measurable
>without great difficulty with a full spectrum analysis, no?

Maybe. I haven't pursued it from that direction.


>Maybe it's time to write a grant.
>
>David Love

I'm ready. Getting paid for educational research would be a novel 
experience. We will need someone to do the paperwork and deal with the 
bureaucracy though. I plan to be busy in the shop.

Ron N