Soundboard crown

[Ron Nossaman]

>However, I am asking myself if a soundboard always needs  crown in order to
>work properly?

Define "properly". Soundboards are typically crowned to provide more 
stiffness for the given mass. They become stiffer as the crown is 
depressed. That stiffness and spring resistance against the spring 
downbearing load of the string plane provides the impedance match for what 
we occasionally consider to be good tone in a conventionally built piano. 
There is no single one thing you can point to, nor will there ever be, that 
accounts for piano tone production. This includes soundboard crown.


>I heard about some old pianos with no measurable crown that sound very good.
>I have even seen some where no crown seemed left, yet the performance was
>very good.

Everyone has heard of these pianos. Most of them are owned by the guy who 
bought the new Corvette for $100 because someone died in it. How many have 
you actually heard for yourself, and what was the condition of the other 
dozens, if not hundreds of factors involved in this assessment?


>So, why is a crown necessary?

To provide the necessary stiffness under load - if it was designed that way 
in the first place as most of them were.


>Would a flat board, but with enough downbearing for teh strings, work or
>not?

If it is still stiff enough to provide the required impedance to the 
strings, through accident or design, yes. Can you assume that a flat board 
will be fine if you just add downbearing (as has been done many thousands 
of times for many years by rebuilders lowering plates on old flat boards), no.

Ron N