Crown

[Michael Wathen]

>      It also follows that a crownless soundboard will never operate
>perfectly, as there is no way to transfer the strings potential energy into
>the piano's structure, Because of this loss of "Arch", a link is missing that
>cannot be replaced by 1) holding the board up with bridge cut kerfs, 2)
>wedging up the board against the framing, ( this just limits the boards
>movement), 3) adding more downbearing pressure, ( this applied to a totally
>flat board will actually attempt to contract the case).  
>


First, lets straighten up the syntax again.  The words we need are
"coupling" and "impedance".  Coupling describes how the energy in various
systems translates the energy from one system to another, and impedance
describes the actual measurement of the exchange (usually a Force/Velocity).
Potential energy is the energy that exist in a given system a specific time.
One could say that the potential energy in a string at rest is ZERO if you
exclude the potential energy due to gravity.  Now, when the string is
deflected from its rest position to a maximum distance from that rest
position the situation is as such:  The total energy in the string is in the
form of potential energy.  The total energy in any system is the sum of the
Kenetic energy (moving energy) and the potential energy (energy about to be
given up to kenetic energy).  Back to the string, a little while later the
string is swinging back (due to of a restoring Force) by its point of rest.
At that particular time the potential energy is zero and the kenetic energy
has every thing.

A standing wave is the action of energy caught in a system that travels back
and forth within the boundaries of the material in a periodic sort of way.
It can be equated in some sense with resonance. But better said resonance is
the expected frequency or frequencies of a given body.  Resonance tells us
that with all the given properties of a string we can expect the energy to
create standing waves with certain frequencies.  It can also tells which
frequencies we can not expect, which is why the standing wave on the string
produces the tone that it produces and not some other tone.    

In spite of all the arguments thus far I have not seen anything to convince
me that a board has to have crown or even down bearing for that matter.

  Mr. Foote's message is very good until this conclusion.  
****************************************************************************	

Michael J. Wathen			Phone:	513-556-9565
Piano Technician			Fax:	513-556-3399
College-Consevatory of Music		Email:  Michael.Wathen@UC.Edu	
University of Cincinnati
Cincinnati, OH 45221-0096

http://www.uc.edu/~wathenmj