Installation Notebook:
Sound installed in a Bachman HO Consolidation
The Light Mountain uses the same tender, too!
The tender of the Consolidation looks as if it were designed with a 28 x 40 mm speaker in mind. A minor bit of plastic shaving and two small (white in the photos) pieces of plastic and you are styling!
The coal load was perforated with a #70 drill to allow the sound out the top. Some coal loads will require a bit of material removal to clear the speaker frame.

Bruce removed the Bachmann board and wired the Tsunami directly to the rail power, motor and headlight connections. Removing the Bachmann board provides room for the Tsunami install, leaving the mounting boss in place, so the shell can be screwed to the tender floor. A rear light could easily have been added at this time.
The Bachmann Light Mountain loco uses this same tender for the most part. The internal Printed Circuit Board is different. However, if you are removing the board, as Bruce recommends, the install is the same.
After tweaking a few CVs, the loco was off and running.
Be aware that there are several tenders out there for the Consolidation. This tender is about 4 inches long. The shorter (about 3-1/2 inch long) tender will need the SP-28R-08 speaker, but the rest of the install is the same
Speaker Mounting
Yes, the speaker is mounted with the magnet
up! Sound comes out both sides of a speaker. The sound coming off the
magnet side of the speaker goes out through the coal load. The sound
coming off the other side of the speaker goes into the shell (which acts
as an enclosure) and a small amount makes its way out the small opening
in the coal doors.

Here is a photo of an earlier install which used a smaller speaker and larger holes in the coal load. This photo does show the speaker installation detail a bit better.
Lights
Some of these locos use bulbs and some use LEDs. If your loco uses LEDs, wire an resistor in the white decoder lead (750 to 1200 ohms, 1/8 or 1/10 watt, will do - I use 750 or 820 mostly). If your loco uses bulbs, connect them directly. If you are unsure, put the resistor in. If you don't get a light, take it out!