Too efficient dampers?

[David Love]

More than the material, the question is what makes a damper system more or
less efficient in terms of how fast the cut-off is.  I have used a variety
of damper felt and not noticed an appreciable difference in the cut-off
time due to differences in felt manufacturers.  However, there are
differences in how well the felt is fit to the strings, how well the
bichord dampers fit between the strings, and the number and combination of
trichord felts versus flat dampers, avoidance of the string nodes and the
overall length of the dampers (longer dampers do not always cut off
faster).  

Beyond that, cut-off time seems more related to the total weight in the
underlever (or the strength of the spring in an upright).  There is a
tradeoff with quicker cutoff due to more weight in the underlever, and
that's a greater difference in feel in touchweight between damper pedal
engaged and unengaged.  

Before installing new damper felt it is wise to review the weight of the
underlevers with a gram gauge and either adjust spring tension (if there is
one) or lead patterns to make a smooth transition from bottom to top
(replace the guide rail bushings too if they have too much play or are
hard).  Renner's guide that comes with the underlever installation kit is
useful here.  After that, when I am installing damper felt I try to listen
for the length of time of the cutoff and plan my transitions from trichord
to trichord/flat combos to flat dampers so that there is no appreciable
jump in cut off time in either direction.  (You'll notice on Yamaha pianos
the last flat damper is cut so that the right hand unison is free to
vibrate.  This even allows the transition from flat dampers to no dampers
to be a little smoother. )   I do this either by playing or plucking the
string.  If the damper is touching the node you can hear it and test it by
touching your finger to the point at which the damper ends and plucking the
string to see if you get the same harmonic that you are hearing.  Position
the felt in or out if necessary to get off the node.  If you are replacing
damper felt from an older piano, pay attention to what's there and the
length of the dampers.  A lot of those damper guys in the factory knew what
they were doing.  Go slow and fit and seat as you go.  I find that doing
good damper work with smooth cutoff just plain takes time.  

David Love
davidlovepianos@earthlink.net


> [Original Message]
> From: Sarah Fox <sarah@gendernet.org>
> To: Pianotech <pianotech@ptg.org>
> Date: 7/7/2003 9:47:16 PM
> Subject: Re: Too efficient dampers?
>
> Hi John (and Terry),
>
> > I have always known that Yamaha had an extremely efficient damper
system.
> > The cut-off is almost instantaneous.
> > A music teacher at a boarding school, where I tune the pianos is
> > contemplating the purchase of something else, the present grands, would
> cost
> > too much to bring up to a good level.
> > Anyway, he said he hated Yamahas, and I thought brightness of tone, but
we
> > narrowed his dislike, down to the sound being cut off too abruptly.
> > Have others heard of this complaint?
> > If they have, were they able to solve the problem to the customers
> > satisfaction, and what did they do?
>
> I regularly play pianos ranging from a very harsh cutoff (my Hamilton) to
a
> rather sluggish cutoff (my friend's Knabe, which needs new damper felts).
I
> tend to get used to whatever I'm playing, after I've had time to practice
on
> it for at least a few days.  However, I do dislike too abrupt a cutoff,
just
> like the music teacher.  I think this dislike might be similar to a
dislike
> of "dead" acoustical environments (which also bother me in an aesthetic
> sense).
>
> I'm very interested in the thoughts of others on this subject.  I'll
> probably be wanting to replace the dampers on my Wissner grand and would
be
> interested in achieving a "medium" damping action -- nothing too
> abrupt/efficient/Yamaha-ish.  Any recommendations as to replacement
> material????
>
> Peace,
> Sarah
>
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