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? 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? 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. How do most CC boards compare with RC&S boards in terms of spring rate? 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 it's time to write a grant. David Love davidlovepianos@comcast.net -----Original Message----- From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Ron Nossaman Sent: Friday, February 18, 2005 7:47 AM To: Pianotech Subject: RE: More CC vs RC questions was RE: Killer Octave & Pitch Raise >Ron: > >Could I ask you to amplify a bit on what progressive and lower and >higher spring rates mean? > >David Love Board A has a 5mm crown, deflects to 3mm crown under load. Board B has a 7mm crown, deflects to 3mm under an identical load. Both are supporting identical loads with identical remaining crown, but A has a higher spring rate, and B will move farther under a given impulse than A. Rib (beam) deflection is linear. If 10 lbs deflects a rib x distance then 20 lbs will deflect is x*2 distance and 5 lbs will deflect it x/2. That's a constant spring rate. Soundboard assemblies are non linear in deflection. If 50 lbs deflects a board x distance, 100 lbs deflects it less than x*2, but 25 lbs deflects it more than x/2. As the load increases, the spring rate also increases. That's a progressive spring rate, and I think the panel compression is responsible for this. Ron N _______________________________________________ pianotech list info: https://www.moypiano.com/resources/#archives
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