impedance (was negative crown_

Delwin D Fandrich pianobuilders@olynet.com
Wed, 30 Dec 1998 20:01:38 -0800



Frank Weston wrote:

> Del,
>
> Please don't get your shorts in a knot.  I don't think I said that
> understanding the principles of mechanical impedance and applying them was
> too complex a subject for a piano builder or designer.  Carpenters do it
> every day.  The point I was trying to make is that the actual numerical
> analysis is extremely complex when done on a purely theoretical basis.  On
> the other hand, building a physical model (a piano), testing it, applying
> the basic principles (impedance function of inertia and springiness) to
> modify the model, is a workable and practical approach.  Is this the
> approach you employed?
>
> Frank Weston

  ---------------------------------------

Many, if not most, piano technicians are quite convinced that they cannot
possibly understand even the basics of how pianos work acoustically.  And
that's to bad, because it would help them considerably in their attempts at
voicing them.  And rebuilding them, for that matter.  Not every piano
technician should become a piano designer.  For one thing, there's not much
demand for piano designers.  But neither should there be a fear of opening up
the subject and tossing a bit of light on some of the darkness.  I get a bit
testy at anything that fosters and encourages that fear.

Yes, mechanical impedance is some difficult to calculate and to predict in
precise terms.  Its not all that hard to measure, however.  And the basic
principles are not that hard to explain or understand.  I've done several
classes on this with some success.  Sure I leave out a lot -- I don't even
mention the imaginary parts, for example.  But we get to the essence of the
subject as it pertains to the piano and I think folks leave with a better
understanding of how the piano works than they had when the class started.  At
least that is what I have attempted to accomplish.

And, yes.  My basic approach to the problem is to learn what I can about the
theory of how a thing should (might?) operate.  Think about it for a while.
Build something that I think should work.  Listen to it, measure it and then
figure out why it doesn't.  And start over.

Regards,

Del



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