Caster Cups

[Billbrpt]

In a message dated 5/4/98 2:57:02 PM Central Daylight Time,
prescottpiano@juno.com writes:

<< Several years ago I was at an Arizona State seminar where The comment was
made that  putting a grand piano on caster cups would improve the tone and
volume of a piano and make a 5' grand sound like a 6' grand.  Especially if
the piano were on a concrete floor, even if it were covered with tile, carpet
or wood.  >>

    This has been demonstrated many times but I know of no hard data to
support it.  I first saw this demonstrated in a voicing class by Wally Brooks.
It was at an Annual Convention in a room where there is deliberately a lot of
material to absorb sound, not let it carry.  He showed a number of things to
do with a small Steinway grand to make its sound carry.  The very last was the
placement of caster cups and I was truely impressed by the before/after
difference.

     Wally explained that there is a lot of energy which actually travels down
the legs of the piano and that it can be lost by the carpeted floor acting as
a "heat sink"  (sound energy is like other forms of energy and can be
absorbed).  The caster cups serve as an insulator and cause the energy to not
drain directly into the floor.

    If this is really true (and I cannot prove that it is), you can use the
same knowledge to your advantage if you wish to quiet an overly loud piano.
The room should have abundant soft surfaces to absorb the sound.  Soft
material under the piano will help.  It seems logical that styrofoam or other
soft, absorbant material placed in or under the piano will serve to quiet it
down.  If a customer has a vertical in a small house or apartment with no
carpeting and the complaint is that the "piano is too loud", placing a blanket
over the back and suggesting a rug for underneath the piano can make a
significant difference.  The more soft surfaces there are in the room,  the
less that sound can be reflected.  

   When I tune a piano at a convention in one of those large meeting rooms, I
am aware that the room itself is designed to absorb sound (noise), not let it
carry.  All of the surfaces are soft.  There is air conditioning/ventilation
noise.  The piano may be placed on a portable platform.  A large grand piano
will cause such a platform to sag if there is no distribution of its weight.
It is easy to imagine that much energy can be lost directly downward, into the
platform and be lost in this kind of situation.

    My solution for this, and I have seen others do similar things, was to
place the piano's casters on pieces of 2 foot sqaure plywood that would
distribute the weight over a wider area and would also serve as reflectors of
any energy that would travel through the legs and into the casters.  I used my
spare plywood squares to put directly under the piano so that there would not
be a soft, carpeted surface there.  I even placed the unused music desk under
the piano in the open position as a sort of deflector.  Someone remarked to me
that he had seen the music desk there but thought that I had just casually put
it there but I explained that it was specifically placed for a reason.

    The suggestion of an emperical test that was made would be of great
interest.  In such a situation as I described, get decibel meters to measure
the output of the piano placed on a platform in such a room with no sound
reflectors or insulators, then measure it after any and everything that could
be done to enhance the carrying power (and perhaps all the steps in between).
Using a Yamaha Disklavier or a piano equipped with a PianoDisc system would
serve as a good control so that the amount of energy put into the piano would
remain a constant.

   I recall a review by Yat-Lam Hong in the PTG Journal of a NAMM show where
he had noticed that a Fazioli piano had been displayed with 6" glass caster
cups (risers) and that a mirror had been placed under the piano.  While he was
told that the mirror was there so that people could view the soundboard
without bending over to look, he speculated that these two steps had been
taken for acoustical reasons.  (This was a good example of not necessarily
believing or taking at face value something that someone has said.)  This
observation and the demonstration by Wally Brooks gave me ideas on what to do
when I had my own piano to tune and wanted it to be heard in a large, sound-
absorbant hall.  I saw afterwards that others had taken up the basic idea and
were supporting the piano on such platforms in various ways.

Bill Bremmer RPT
Madison, WIsconsin