Yeah, that was my first reaction. If the speaker has in fact been damaged, IMHO it's more likely the sound would have also been garbled rather than just show up as a volume reduction (FWIW it sounds to me more like a hardware design or software issue, especially if it has always been low volume).
I think I'd try a breadboarded replacement speaker first to confirm that's really the problem before attempting to dig the old one out and replace it. I have some small replacement speakers (about an inch across, w. plugs) I could send you -- if interested, I can photo the plugs for compatibility first. Let me know.
I have spare speakers, but not hooked one up yet. I am thinking they won't help. The sound is clear, that is why I think spkr, but want more options before I pull it. To hook one spkr up to test is a little challenge. Cut tie holding wires, find connector to match MTH connector (I don't have one) test. With no connector, option is to somehow get spkr wires connected to harness pins. Pins are SMALL!
Other odd things are that the sounds that are there are clear! Engine noise, announcement buttons, but LOW volume. The horn button does not work, nor the bell, but the horn will sound when one of the quick buttons are pushed for it.
Bell has no sound, and the couplers fire, but no sound when they do. The sound on/off button works (remember, this is DCS) and the headlight works and changes with direction change. All in all, it runs great, just missing the noises.
It is the lead unit in an A-A set. Just to see if putting the dummy to it makes a difference, it does not. The rear couple fires as it should.
I have a bad feeling that even if I dug out and replaced the speaker....I would have the same issues. Perhaps GRJ or GGG, Vernon Barry, or that guy with 1000 in his moniker. Everyone should know more than I do!
Thanks, Greg (I did get to run some trains today!)