Crown Measurement

[Delwin D Fandrich]

Michael,
Sorry this took so long. I've been a bit busy of late.


Michael J. Wathen wrote:
> 
> 
> What are people generally saying when they say a board has no crown?

Usually they mean (or at least think they mean) the smooth upward curve
of the soundboard from its edges to the center of the board. The
soundboard surface has often been described as having a shape like a
segment of a ball that is approximately 120 feet in diameter. That this
ideal has never been realized in real life is another matter. One that
most of us would rather ignore if we can.


> Are they referring to negative bearing across the bridge?  

Not usually. "Down bearing," or "string bearing" is another matter
entirely. You can have a soundboard with lots of crown and no string
bearing and you can have a soundboard with no crown but with lots of
string bearing. Neither will work very well, but both are possible.


> With all this
> discussion I am getting a little worried.  The 6'5" Chickering in my living
> room has the original board and its been shimmed (not by me). It was built
> in 1895.  I plan to post a short wave file as soon as I can get a good
> pianist to come by.  I like the piano but maybe it is a little weak.


Not surprising. Soundboards don’t last forever. And shims rarely result
in any acoustical change or improvement in the performance of the
soundboard. The cracks were not the problem. Age, and the changes
brought on by the ravages of time are the problem.

I'm preparing a Journal article dealing with this very subject. It's a
rather lengthy and contains far more information that I'm prepared, or
willing, to go into here—I don’t consider pianotech to be an
satisfactory substitute for the Journal. If you can’t wait and have a
specific question, I’ll do my best to answer it.

—ddf