Soundboard crowning

[Ron Nossaman]

Hi Frank, happy to have you aboard. With soundboards, it's pretty much the
same discussion wherever you come in, so a history of participation
shouldn't really matter.

>What is characterized as old-style or new-fangles is not necessarily so.  
>Much of what we do today in building pianos is not far removed from the way 
>it was done 100 years ago.  It is not an either-or situation. Most 
>manufacturers today do cut a crown in the ribs, but we also rely on the 
>effects of "natural" crowning. 

The fact that processes haven't changed all that much in 100 years is
pretty much the point. There are traditional problems in specific areas of
the scale that are the result of traditional soundboard design and assembly
methods, and remain so because the designs and methods haven't changed much
for a very long time. A deflection analysis of the rib scale of these
hybrid rib/panel crowned boards under string bearing load indicates to me
that the bulk of the load is being carried by the panel. At least, the ones
I've done the analysis on. While that doesn't make it entirely one or the
other, that does make it primarily a panel crowned board. Also, for what
it's worth, the term "natural" crowning seems to carry entirely too much
automatically assumed validity as an assembly method. "Panel" crowned, as
opposed to "rib" crowned might be both more accurate, and less prejudicial
a nomenclature than "natural".   



> We continually test ideas in experimental 
>efforts to learn more about how we might build a better piano.  More often 
>than not, the experiments raise more questions than they answer!
>
>Frank Emerson, engineer
>Mason & Hamlin

On the new "A", for instance, are you using a rib scale similar to the old
ones? The rib dimensions on the old pianos indicated they were at least
mostly, if not entirely, panel crowned. If someone in my area was selling
them, I'd have already been underneath one of the new ones and taken my own
measurements. There aren't any handy, so I'm curious. Also, getting back to
the original problem with the new "A", what else could such a drastic lack
of sustain be in the "low treble" (killer octave) besides a soundboard
problem? The problem was there whether the area was plucked, or played. The
crown in the offending area wasn't measured ( I don't know why ), though it
was minimal on the long rib. The bearing was negative in the area with the
sustain problems. If the soundboard crown is also negative, what else could
it be called but a soundboard problem? Bruce, it sure would help to know
what the crown status is directly under the problem area in the piano you
reported on to either indicate or eliminate the probability of the plate
being set too high in the first place. In any case, how can the results of
all these experiments to improve the product result in the same old tonal
problems we have always seen? Maybe I'm just being unrealistic, but it
seems to me that an improvement ought to be detectable by, if nothing else,
the absence of a problem it was intended to cure.

Regards, 
Ron N