Impedance problem

[baoli liu]

Hi David,

You happed to check E4 and F4 and found similar
phenomenon? the mode of soundboard could be a
reason,just guessing.
Baoli


--- David Love <davidlovepianos@comcast.net> wrote:

> 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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