Steve Greatrex has certainly got a real problem on his hands.  Room
acoustics and the way they affect our instruments is a complex subject.
A large musical box has a wide range of acoustic characteristics
ranging from very low to high notes and all the harmonics and
resonances between.  Even between Polyphons, playing in the same
environment, there can be large differences in sound quality, but
a good one in a poor environment can be very disappointing, especially
if it has been previously enjoyed in an ideal environment.

Steve doesn't tell us the relative sizes of the 'before' and 'after'
rooms but I would guess that the latter is a purpose built extension to
his house built specifically to house his collection.  Here we have the
problem.  Modern building standards do not absolutely require concrete
slab floor with top insulation and dry-lined walls, but these are the
most usually used and are the cheapest.  They are, however, the worst
for acoustic liveliness.

In its previous home, the Mikado Polyphon was sitting on a suspended
solid wood floor and the walls would have been traditional solid brick,
plastered.  In spite of the carpet, there would have been substantial
low notes transfer into the wooden floor which would then act as a
soundboard.  The walls would have been bright in their response to
incoming sound waves and responded with a good reflective power.

The acoustic brightness of any surface is dependent on its relative
stiffness so a traditional wall is very good for acoustics.  Of course,
this sort of room may be ideal for a large Polyphon but may be just too
much for a loud fairground organ.

The new room has a concrete slab floor which now lacks the soundboard
characteristics of the suspended solid wood floor.  The topping of foam
insulation and chipboard makes things even worse.  There is little mass
to the surface layer and it is made of chipboard which by its very
nature is acoustically dead.  The carpet makes things even worse.  The
walls are dry-lined which means that the surface layer is a thin layer
of plasterboard with no stiffness behind it, again of low mass and
acoustically dead.

So what are the solutions?  Firstly, move the Polyphon back to its old
abode and put your player pianos and other similar instruments in your
new room.  Any reasonable wife will allow you to display your toys all
around your house rather than insisting they are all kept out of sight
and in one place.  Small cylinder and disc musical boxes may be okay
in your new room as long as they are exhibited on a solid wooden table
which has its own resonant characteristics.

If there is no alternative but to house your Polyphon in the new room
you could try sitting it on a large wooden base, like some form of
raised plinth.  This would need to be made from solid wooden planks.
There is not a lot you can do with the walls.  You could remove the
carpet and put down a few rugs, leaving more reflective area on the
floor, but this will probably not make a discernible difference.  A
non-purist idea would be to add some form of electrical amplification
incorporating selective bandwidth amplification, with a contact
microphone discretely mounted on the back of the soundboard.  I'm sure
I will get criticised for such a remark!

I hope Steve finds a solution soon as I will be visiting him this
summer so will be able to listen to the Polyphon myself.

Nicholas Simons, GB