String termination devices

[Delwin D Fandrich]

----- Original Message -----
From: "Overs Pianos" <sec@overspianos.com.au>
To: <pianotech@ptg.org>
Sent: November 12, 2001 12:14 PM
Subject: Re: String termination devices


>
> It seems to me that the idea of controlling the buzzing with silicone
> rubber would be a wonderful way to pull energy out of the vibrating
> string to shorten sustain.

Sustain did seem a bit short through parts of the scale on the piano I saw,
but I expect there are a variety of reasons for it. It was my
impression--without being able to measure it--that downbearing was
non-existent. Whether by intent or by accident this will certainly have an
effect on soundboard stiffness. I doubt there would be enough energy loss
between the leading edge and the center post of the bridge termination
device to notice. But, as noted, I didn't have a lot of time with the piano
and the issue didn't come up in any of the experiments I conducted.


>
> The other negative aspect of bridge agraffes is the resultant loss of
> bridge wood height. I've written before on the list about the
> influence of bridge height on the sustaining qualities of an
> instrument. The Stuart string height is 32 above the sound board
> panel (long bridge ie.), while his agraffes hold the wire 8 mm above
> the bridge wood. With only 24 mm of bridge wood height, I believe the
> note to note sound board impedance will be less uniform. I have seen
> just two concert grand pianos from different makers with 24 mm high
> bridges. I didn't care for the tone of either, and I hold the bridge
> height accountable for part of the crime.

I don't consider this to be a negative aspect of either the bridge agraffe
or the termination devices I've experimented with or as used by Stuart. If
the designer agrees with you--I don't, necessarily--on the bridge height
issue it's a simple matter to raise the string plane the requisite amount.
(Keeping in mind that bridge height is simply one small aspect of a rather
complex whole....)

>
> Look up the five lectures
> on the acoustics of the piano.
>
> http://hem.fyristorg.com/5_lectures/
>
> It is some years since I read these documents, but they certainly
> mention the negative effects of building sound boards with lower
> ribs. I am convinced that the bridge height is just as important an
> issue.

I have the book and have read it. But that doesn't mean I agree with
everything I've read either there or elsewhere.

Del