Don Mannino 74473.624@CompuServe.COM
Mon, 17 Jun 1996 10:56:06 -0400 (EDT)

David Sanderson Wrote:

>>Well Keith, this is a different approach!  The cure always reveals the cause,
if we can properly analyze.  What occurred when the upward pressure was
introduced? More down bearing, crisper termination point, more crown,
anything else? Well yes, increased amplification transferred through the back
posts via this screw. . . . .<<

Watch that word - amplification. Just one of my little pet peeves -
amplification is not properly defined as making something louder. Amplification
means that something is added to the original to expand on it or make it larger.
The key is that something is added to something else to make the final result
larger. In the case of an audio power amplifier, energy is transferred from the
power supply into the output circuits.  In the case of the piano, there is no
other energy source than the pianist.

In the above topic, one should think more in terms of matching impedance. When:
1. The soundboard impedance in a particular area matches the energy level (mass
and amplitude) and frequency of the string motion, and:
2. There is good energy transfer (clean, tight string to bridge contact,
sufficient bearing, etc.)

Then the system works efficiently and more volume is produced. Adding stiffness
(screw to the back post) is usually the opposite of adding mass (key weights in
the bridge), and so it isn't likely that both would produce the same results in
one situation.  Come to think of it though, the weights should both lower the
resonant frequency of the system while possibly increasing the impedance.  I'm
not quite well versed enough in these things to know for sure. Need one of the
resident engineering types to jump in here.

Rescaling can also adjust the impedance match by adjusting the string energy
level and the stiffness of the soundboard system through increased bearing

Hope these stray thoughts are germain.

Don Mannino RPT

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