Soundboard Weights

[Delwin D Fandrich]

----- Original Message -----
From: "Tom Servinsky" <tompiano@gate.net>
To: <pianotech@ptg.org>
Sent: March 09, 2002 12:45 PM
Subject: Re: What a nice surprise - technically OT


>
> >
> > Normal pradctice is to  harden the hammers.  An effective compensation
> > is to secure weights to the bottom of the board.  Or replace the board
> > with one properly designed and assemsbled.
> >
> > Newton
> Adding weights to the bottom of the board is a new on me. Would please
> elaborate.
> Tom Servinsky,RPT
>

Tom,

Soundboard impedance is established by three primary characteristics of the
soundboard assembly; its mass, its springiness, and its internal resistance.
With most of the pianos exhibiting 'killer-octave' problems the problem lies
with the reduction of springiness that has taken place in the soundboard
assembly relative to the time when the soundboard assembly was new. Or at
least when it was functioning properly. There is nothing you can do about
the systems internal resistance and there is not a lot you can do about the
loss of springiness except add auxiliary springs to the system, but this is
a technology that few have yet to embrace so little is known about the
procedure or its long term results.

The other thing you can do is add some mass by means of brass (at least that
is what I've used) weights attached to the underside of the soundboard along
the bridge line. These are installed by drilling through the brass weight
(start with something in the neighborhood of 75 to 100 grams) and screwing
it to the bottom of the board. The screw should extend well into the bridge
body. Put one in the area of shortest sustain and see what happens. You will
have to experiment with various amounts of mass to find the amount that
gives you the best results. Once you've settled on a certain amount of mass,
put a bit of PVC-E adhesive between it and the soundboard (to keep it from
buzzing) and tighten the screw thoroughly. Several weights in the 75 to 100
gram range spread between the various ribs are better than one two to three
hundred gram weight stuck in just one place.

This is not the same as a new and functional soundboard, but it is a lot
cheaper. If you don't like the results you get from these weights simply use
a screw and soundboard button on to cover the hole(s) you've made and forget
it. A new soundboard will then be the only solution.

Del