ETD question re: unisons

[Meyer Carl]

Tom:  If I'm not mistaken, the wapin bridge claims better sustain  as it's
primary value.  It follows then that due to bridge impedance a vertical
vibration will result in a short sustain, a circular vibration a medium
sustain and a horizontal vibration will have the longest sustain.

Now if you can shorten the time that vertical vibration takes place, more
energy is available to increase the duration of the medium sustain of the
circular vibration.
If that is in fact true that the wapin bridge accomplishes that, I can see
that may be why it improves sustain.  It may be taking energy at the
beginning or(prompt sound) and transferring it to the aftersound.  That may
be a good thing and may sound better, but I can't yet visualize how that
happens when you straighten up the bridge pin.

I suspect that if the string goes circular immediately, it will remain so
only for a short time.  However,  by that time the pianist will have decided
to hit some other note, so it doesn't matter.

Velly interesting.

Carl Meyer



----- Original Message -----
From: "Tom Cole" <tcole@cruzio.com>
To: <pianotech@ptg.org>
Sent: Friday, February 16, 2001 6:08 PM
Subject: Re: ETD question re: unisons


> Carl,
>
> I seem to remember, from a class on the Wapin bridge, that the cant of
> the front bridge pin causes the vibrating motion to precess from
> vertical to horizontal, etc., and that the vertical pin on a Wapin
> bridge allows for circular motion almost immediately.
>
> I don't know if this helps you any but I thought it might bear on your
> question in some way.
>
> Tom Cole
>
> Meyer Carl wrote:
> >
> > Hello Mr. Curious:  I am curious2.
> >
> > Yes, I read that  and think that he really has a handle on the reason
for
> > prompt sound and aftersound.
> >
> > I had a loose leaf notebook with a Xerox of that article along with
articles
> > by Jim Ellis, a couple of guys from Baldwin, both from the journal, and
a
> > comment from Ed McMurrow about horizontal vibration of strings from his
book
> > "The educated Piano".  I must have loaned it out since I can't seem to
find
> > it.
> >
> > As I understand it, a string will vibrate vertically (grand piano) and
the
> > impedance of the bridge will be low, hence dissipating energy at a fast
> > rate.  Then due to imperfections the strings vibrations will slowly
change
> > to elliptical and then progress to horizontal.  At the horizontal mode
the
> > impedance of the bridge will be much higher resulting in a slower rate
of
> > dissipation.  This is easily understood by comparing a capacitor in an
> > electronic circuit, discharging into two different resistive loads.
> >
> > In the case of the piano, the two different loads are not switched
abruptly,
> > but gradually.
> >
> > One statement I read was that good pianos don't have horizontal
vibrations.
> > Really?
> > I guess that if the strings were perfectly leveled, the hammer perfectly
> > mated to the strings, then the horizontal vibration would be minimized
or
> > maybe delayed.
> >
> > Now my question would be.  If that were true would the shape or point of
> > shift in the amplitude plot be delayed?  That would be an interesting
> > question to test with a set up to plot the timing of the transition from
> > prompt sound to aftersound with different string levels etc.
> >
> > Anybody care to render an opinion?
> >
> > Carl Meyer
> >
> > ----- Original Message -----
> > From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
> > To: <pianotech@ptg.org>
> > Sent: Thursday, February 15, 2001 9:04 AM
> > Subject: Re: ETD question re: unisons
> >
> > > I am curious.... just how many of you have read Gabriel Weinreichs
paper
> > "The
> > > coupled motion of piano strings" ?
> > >
> > >
> > > --
> > > Richard Brekne
> > > RPT, N.P.T.F.
> > > Bergen, Norway
> > > mailto:Richard.Brekne@grieg.uib.no
> > >
> > >
> > >