SW heresy?

[Isaac OLEG]

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Shapes of curves are (for what I understand) a compilation, evened.

The first intent is to even the touch weight parameters.

To me these are so linked to psychoacoustic response that any modifying of
the tone is changing the weight as perceived.

A piano action may insert harmoniously in the instrument not have its own
parameters as this can be perceived as a foreign action vs. tone and feel of
the piano.

Best regards.

Isaac

-----Message d'origine-----
De : pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]De la part
de Sarah Fox
Envoyé : dimanche 22 août 2004 07:31
À : Pianotech
Objet : SW heresy?


Hi all,

Thanks for the advice about techniques to even out the SW curve!  That
should give me a variety of techniques to use/combine in order to even out
the jags.

But the question is one of what my target curve should *really* be.
Hmmmm....  My thoughts:

The unmodified SW curve is obviously very linear.  (Yes, I know what linear
means.  I "minored" in mathematics, sort of -- except that my U. didn't
officially recognize minors).  Stanwood's curves, OTOH, are all concave
downwards.

I was advised off list that I shouldn't force the hammers to artificially
conform to a standardized Stanwood curve but to simply even out the jags to
make the action smooth from bottom to top.  There's something to be said for
this idea.

But as I got to thinking about the SW curves, I was wondering, where do they
REALLY come from?  That is, where does the shape come from?  I suspect the
hammer manufacturing people might be able to enlighten me as to this.
(Ray???)  I'm *guessing* that the felt is denser than the molding, and when
the hammer becomes skinnier, it loses more felt than molding, resulting in a
more precipitous dropoff in weight at the higher end.  This would occur with
a constant hammer length and a linear variation in hammer and molding (and
felt) width.  Am I anywhere close on this idea???

Contrast this function with other functions that might actually relate to
optimal hammer mass:  String length and mass both decrease with the note
number, with a function that is concave upwards.  Note frequency increases
with a function that is concave upwards.  Note period (inverse of frequency)
increases with a function that is concave upwards.  The Stanwood curve seems
rather meaningless with regard to any of these functions.  For instance, it
might be good to match hammer mass to string mass by some proportion.
Right?  As the scale goes up, string length and mass approach an asymptote
of zero.  Therefore, shouldn't hammer mass approach an asymptote of zero?
Instead, the curve starts taking a dive in the treble.  If the scale went up
well past 88, hammer mass would eventually crash to zero.  Because these
curves do not have the same form, the relationship between hammer and string
mass is anything but constant.  That doesn't make sense.

So is this something that is the way it is just because of tradition --
because the cauls are built that way, and that's what ya' get?

Now that I look at my linear SW curve (with jags), I'm wondering if this
isn't REALLY a closer match to something meaningful (like string mass) than
the idealized Stanwood curves.  Any thoughts, y'all?

Peace,
Sarah



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