Hammer mating and spring rate in soundboard design

[David Love]

To follow up on a thought I posted regarding hardness of hammers
matching with soundboard design and spectral analysis.  Below is a page
from the five lectures in which a spectral analysis is performed on
hammers of varying degrees of softness.  Figure 12 is a nice
illustration of the differences between soft and hard hammers with
respect to the strength of the harmonics they produce--something we all
know but this provides a nice way to picture it.  Somewhere along that
graph is probably a balance of partial strength that most of us would
find desirable in a satisfying, complex piano tone. 

Again, the relationship to soundboard design that I'm curious about
might be in the area of spring rates and that relationship to how hard
or soft the hammer needs to be to deliver something desirable at the
attack point and still provide the full spectrum of overtones that we
want.  If a particular soundboard design that produces a lower spring
rates forces us, for the sake of a pleasant attack, into the use of too
soft a hammer to create that overtone balance, the price paid for too
low a spring rate might be in the strength of certain partials
concomitant with the use of that particular hammer and a resulting nice
and round but maybe somewhat dull or unexciting tone.

The next question, then, is whether there is a relationship between CC
vs RC&S soundboards and the resulting spring rates.  As I have heard
RC&S boards that required a fairly firm hammer and ones that required a
fairly soft hammer it is apparent that there is nothing inherent in the
RC&S structure that dictates a hammer density one way or the other.  So
if the spring rate is what is at issue, I can't see why it couldn't be
controlled no matter what style you used.  I wonder, though, whether
there isn't something inherent in the process of CC that produces a
certain spring rate due to panel compression that might have to be
created in other ways with an RC&S board.  How those "other ways" might
also influence tone production is yet another question to ask.  


www.speech.kth.se/music/5_lectures/hall/theory.html

David Love
davidlovepianos@comcast.net