Impedance problem

[David Love]

I am aware of how to deal with the problem--mass substituting for
stiffness, etc..  The question is, why does it happen right in the
middle of a section of the bridge so that it could be avoided in
soundboard or rib design or placement.  

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of V T
Sent: Friday, January 21, 2005 9:35 AM
To: pianotech@ptg.org
Subject: Impedance problem

Hello David,

There is a patent, I think by Mr. Conklin of Baldwin,
that deals with this problem.  Basically, the idea was
to attach a weight on the back of the soundboard right
behind the problem area.  If you are interested, I can
dig up a copy of the patent for you.

Vladan

==============================
I ran into an interesting phenomenon today.  Rebuilt
Steinway A c1915.
New soundboard.  Reasonably poor job but that's not
the issue.  Note E5
was extremely loud compared to its neighbor F5. 
Switched hammers and E5
was still very much louder.  So a clamped a set of
vice grips onto the
rear bridge pins at E5.  Sure enough, the addition of
some mass caused
the loudness to diminish and the sustain to be
slightly enhanced.  The
customer thought so too.  I was surprised that the
addition of mass
would produce an effect so localized without having an
appreciable
effect on F5.  Was I hearing things?  Well clearly I
wasn't, but what
was going on underneath or in the panel that there
would be such an
effect right at that point.  Thinking about it later
it occurred to me
that rib position under the bridge at that point might
have had an
influence.  Comments?

David Love
davidlovepianos@comcast.net 

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