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MMD > Archives > May 1998 > 1998.05.02 > 09Prev  Next

Sounds of Pneumatic vs. Solenoid Pianos
By Karl Ellison

I've been reading L. Douglas Henderson's discourse on the merits of
pneumatic piano actions compared with those driven by solenoids, at

and would like to pose a few questions regarding this topic for the
group to discuss if so inclined.

As stated in Douglas's text, I understand that pneumatic actions
deliver power to the piano action throughout the entire strike distance
(the same as a human finger would when pressing on a key, especially at
low volumes), while electrical solenoids develop their power as they
accelerate through their magnetic field.  Douglas makes statements
indicating that these characteristically different motive forces
affect how a note would sound: one being struck as normal, while the
other 'bops' the note.

I wouldn't think a string being hit with a hammer could care less
whether or not the hammer was accelerated at the start or at the end
of it's travel, that the only thing that would count is the velocity
of the hammer at it's moment of impact.  Thinking back to high school
physics, recall that force = mass times acceleration.  Since the mass
of the hammer remains constant, the only variable that effects the
hammers force is it's acceleration. (Velocity is the mathematical
integration of acceleration over a period of time.)

Given this, does a hammer that is _still_ accelerating as it hits
the string have a different force effect over a hammer that was not
accelerating -- each case having the same impact velocity?  If the
answer to this question is 'no', how _could_ the sound be different,
all else being equal?

It seems to me that hammer velocity at the impact point is what's
important.  I refer to you to "Recording Ampico Dynamics" in the
May/June 1996 AMICA Bulletin.

  [ snip -- I moved Karl's paragraphs about the Ampico hammer velocity
  [ recording system to a separate article (below).  -- Robbie

Since old music rolls have been designed with pneumatic-strike
characteristics, would playing music designed for pneumatic players
really sound different on the newer solenoid pianos?  (Forget the
notion of arranged compositions for the moment -- I'm talking pure
reproductive powers here.)

Do solenoid pianos compensate for their weakness in correctly playing
quiet/fast music in their driver electronics?  Perhaps drive circuits
are now sophisticated enough to know that rapid notes at low volumes
will require a very special electrical curve to produce the same effect
that a pneumatic system would produce.

I am interested in hearing from other MMDers that can comment on any
"earwitness" comparisons they've made in this regard.

Karl Ellison
Ashland, Massachusetts

 [ Editor's note:
 [ Ever since the pianoforte was invented there have been pianists
 [ who believe that the tone can be influenced by body motions after
 [ the note is played, sort of like the golfer's follow-through.
 [ I believe that, although this technique may indeed improve the
 [ muscle control of the golfer or pianist, is certainly can have
 [ no effect on the golf ball or the piano string after it's struck.
 [ The speed of the golf ball, and the sound intensity produced by the
 [ piano string, results only from the energy transferred during the
 [ impact.
 [ It follows, therefore, that pneumatic and solenoid player actions
 [ should be capable of equally good performance, if they both can
 [ "control the swing" as a good golfer does.  A pneumatic system
 [ issues force commands to the pneumatic key motor, so that the
 [ hammer velocity increases steadily during transit toward the string.
 [ The Stahnke SE system issues velocity commands to its electric
 [ key motor, and accelerates only until the commanded terminal
 [ velocity is reached.  Other solenoid pianos issue commands for 
 [ solenoid current or voltage, and so must deal with lots of
 [ non-linearity problems (including coil heating).
 [ But it's only the performance that matters.  There are now enough
 [ transcriptions of music rolls for solenoid pianos that we can
 [ actually make comparative listening tests.  For example, what do our
 [ readers think about reproducing piano music played on a pneumatic
 [ system as compared to the same music reproduced on the Yamaha
 [ Disklavier?  (E.g., "Gershwin Plays Gershwin", Elektra-Nonesuch
 [ CD 9-79287-2.)
 [ Let's hear from the "earwitnesses" who have heard the vintage
 [ music rolls played on both pneumatic and solenoid instruments.
 [ Later we can discuss the reasons for the differences.
 [ -- Robbie

(Message sent Sun 3 May 1998, 02:07:17 GMT, from time zone GMT-0400.)

Key Words in Subject:  Pianos, Pneumatic, Solenoid, Sounds, vs

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