Soundboard Weights

[Tom Servinsky]

Del,
This is extremely interesting. More and more I'm finding myself more
fascinated with inherent design flaws and our attempts ( in the field) to
overcome them.
In the "real world", the world in which we has technicians have to make
things work, many times on a paper-thin budgets, ideas like this gets my
head spinning.
I have a few little grands in the shop which just might find some
experimenting R&D time this week with this idea.
As always,thanks for your sharing your expertise.  Your willingness to share
your ideas benefits all of us.
Tom Servinsky,RPT
----- Original Message -----
From: "Delwin D Fandrich" <pianobuilders@olynet.com>
To: <pianotech@ptg.org>
Sent: Saturday, March 09, 2002 8:41 PM
Subject: Soundboard Weights


>
> ----- 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
>