For example, I was asked to install sound into an O-scale F3A.
The top of the shell had a lot of fan grille openings, but the
space below them was a long rectangle. To maximize the
sound, I used the array shown in (4). A total of 4 (27 mm diam-
eter round high-bass) speakers were assembled onto a sheet of
thick (0.08 to 0.10" thick) black plastic. This was sealed to the
roof of the locomotive so that the sound would be forced out
the top of the loco and the negative pressure (see my August
2012 column
if you
don’t understand the term) gets routed through the loco and
out the openings for the trucks.
Similarly, I had room for two 16 x 35 mm rectangular speakers in
an Athearn Genesis SD75M HO-scale locomotive, as shown in (5).
Okay, once you decide on what sort of acoustic baffling you are
going to use and what size speakers will fit, it is time for the
electronic side of the design.
