Problems With Duplex Scaling Of Pearl River Grands?

[Geoff Sykes]

So setting the back duplex is more or less a process of massaging that
so-called non-speaking length of the string until you like where it is,
correct? With the amount of friction across the bridge pins I understand
that once it is set it's pretty much going to stay there. 
 
Since the front duplex does change whenever you tune the piano, are we
pretty much stuck with wherever it decides it's going to be once we have
stabilized the string with some firm key whacks? I frequently find these
much more objectionable, than the rear ones. And louder, too.
 
-- Geoff Sykes
-- Los Angeles
 
 

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Richard Brekne
Sent: Sunday, August 19, 2007 7:48 PM
To: pianotech at ptg.org
Subject: Problems With Duplex Scaling Of Pearl River Grands?


Tuning the back duplex (and any so called non speaking length for that
matter) can and does involve both the placement of the termination devices
and adjusting the tensions on those segments.

For example... if the back length of a given string is exactly one half of
its speaking length... then this string can be tuned to exactly an octave...
or slightly above an octave, or slightly below. Slightly meaning a pretty
significant deviation.  Friction from the bridge pins is great enough that
there is a window for variation here that will remain stable no matter how
hard you play.  In other words... you can purposely put more tension or less
tension on the back scale relative to the front scale and expect it to stay
there over long periods of time. Or you can if you choose equalize the
tension to the speaking length if you want and expect the same.

If your regular tuning method (for the speaking length) does not include
very large movements of the string... this will not change the tension on
the back length either.

There are a lot of ways of regulating the tension on the back scale. I use a
string stretcher and apply pressure to the string as nearly horizontal and
in a direction away from the bridge pin to do this.  To increase back scale
tension (and hence frequency) I push on the speaking length, to decrease on
the back length.  I find this allows me to actually decide the pitch of the
segment as long as it is within the window of what can remain stable
mentioned above.

Cheers
RicB



Many of the messages on this thread are talking about a tuned front and/or
rear duplex. What that duplex should be tuned to aside, how does one
actually go about tuning either the front or the rear duplex?

-- Geoff Sykes
-- Los Angeles

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