[CAUT] Re. Dollies and projection

[James Ellis]

Alan McCoy asked if there is a consensus whether concert pianos project
better if their legs rest solidly on the floor as opposed to being on a
dolly with rubber-tired wheels.  It don't think there is any consensus, but
I believe more people believe they do than believe they don't.

>From my own experience, I think other factors play a much more important
part as far as sound projection is concerned.  I have heard pianos on
dollies that project just fine, and others that don't.  I have heard pianos
on hard-wheeled casters that project just fine, and others that don't.

I can see a special case involding a wooden floor supported by wooden
beams.  The floor itself becomes a huge sounding board, and if the piano
rests solidly on it, that might have some slight effect on the bass and
mid-range response, but not the high treble response due to the huge mass
of the piano itself.  But don't quote me on this because I have never
measured it, and unless I do, it's an open question.

If a piano is placed over a plush carpet, its projection will indeed be
compromised simply due to the sound absorption of the carpet, not because
the carpet isolates the casters from the floor.

A same piano sitting on a concerte floor will sound vastly different from
the way it will sound if placed over a wooden floor, whether it's on a
dolly or not.  The reason is that the wooden floor in close proximity to,
and parallel with, the piano's soundboard, is coupled to the soundboard by
the air, and also vibrates a little bit - definitely enough to alter the
tone and projection, and perhaps add a few resonant frequencies that may or
may not be desired.

What's going on here is much more complicated than just whether or not a
dolly under a piano changes its projection.  Everything else being equal, I
don't think it makes much difference, provided the piano has a good, heavy,
solid rim and rigid plate, as most high-quality concert pianos do.

Having said that, you definitely don't want a concert grand that's going to
wiggle and bounce when the pianist really gets into it.

Jim Ellis