>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
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