No downbearing ? REVISITED

[Ron Nossaman]

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>To simplify things a bit, can we agree to acknowledge, then ignore the 
>fact that we cannot determine the original bearing set up from measuring 
>the strung piano? Why does there appear to be this growing consensus that 
>these "after stringing" measurements are deceptive, confusing, and of no 
>value?

In my experience, this attitude comes mostly from manufacturer 
representatives who don't care to acknowledge even the remote possibility 
that there might be a problem with their soundboards. The condition of the 
bearing and crown with the existing piano still strung and up to pitch, and 
how it sounds, are the only indicators I know as to what shape the 
soundboard is in and what load it is capable of supporting. A soundboard in 
an un-strung piano will tell me comparatively very little of any use.


>Whether or not the board is being compressed  (i.e. stiffened) by one area 
>of the string scale, if I get readings showing zero or negative 
>downbearing in a section of the piano, is it to be dismissed because there 
>is downbearing SOMEWHERE on the board?

Remember the old joke about the guy who was under the street light at the 
intersection looking for a quarter he had dropped in the middle of the 
block because the light was better here? When you have a killer octave that 
sounds lousy, and you have negative crown and bearing in the same area, how 
can the fact that there is crown and/or bearing in some other part of the 
board make up for that? This idea seems to come entirely from folks who 
don't build soundboards - or from manufacturers or their representatives. 
People who don't build soundboards and don't know any better believe 
information from what they think is an authoritative source. We all do this 
until, mostly by our own efforts, we learn different. Most folks who 
measure crown at all (most don't), do so only at the longest rib. I have 
heard and read "measure crown along the longest rib" at least once a year 
for as long as I have been in this business. If you want some overall idea 
of the load capacity and condition of the soundboard, measure crown and 
bearing over the entire scale. Actually, it might be better stated that 
crown and bearing is of importance only in areas of the scale where the 
piano is actually played.



>With regard to transfer of vibrations, can you, David, or anyone else, 
>direct me to recent discussion that supports this view of the irrelevance 
>of downbearing in this process?  (I will scan the past years posts if you 
>cannot.)  If such is, in fact, the case, and if you could create the 
>hypothetical soundboard with sufficient stiffness WITHOUT employing 
>downbearing's compressive function, is there, in your opinion, ANY aspect 
>of the mechanical transfer of energy from string to bridge ( & board) via 
>bridge pin, that would suffer in the absence of such downbearing?

I can't direct you to a discussion, but if a board can be made stiff enough 
without becoming too massive in the process, I see no reason why a flat 
board with zero bearing wouldn't work quite nicely. The coupling comes from 
the bridge pins (or agraffes). The crown and bearing supply added stiffness 
without adding mass to the assembly in a "conventional" soundboard.

Ron N

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