I think the problem with the sub-woofer in the corner idea is that if you have many trains running you will hear the sound from all of them at once, everywhere in the room.  One of the best points of onboard speakers is that the sound can be localized; people in the next aisle won't hear your train and you won't hear theirs (at least not enough to distract you), assuming you haven't left the volume on full.  If you're running a one man show, that wouldn't be a concern, I suppose.

...the problem with the sub-woofer in the corner idea is that if you have many trains running you will hear the sound from all of them at once

Jurgen, you're probably right.  But since the sounds at idle and during switching are [in my opinion] excellent, the sub woofer could noticeably "kick in" only when the load was great (such as when QSI's Sound of Power turns up the volume).  It's rare to have too many instances of this at once.  And when it does happen, the sound of another train or two rumbling off in the distance wouldn't be too bad, maybe even very realistic (living a couple miles from a mainline, I hear those low rumbles all the time).

I wish I had the equipment and expertise to give this a try.  If it worked, I believe it would be quite a breakthrough in the model railroading world of diesel sound.

Steve

Bass sounds are felt rather than heard and tend to be hard for us to sense "direction". A single subwoofer in the middle of the train room somewhere could be very effective.

It's the treble sounds that are directional, and hey, guess what! Small speakers in model locos do treble frequencies just fine.

If someone would invent an add-on module for a dcc system that would allow some kind of linkage between the loco on the track and a subwoofer, we might get the "killer" sound system. Treble sounds out of the loco, bass sounds out of the sub-woofer on the floor.

You could do it with two decoders programmed to the same address I suppose - at twice the normal cost per sound loco.

More than 1 engine would work and all you would need is 1 woofer per area.

Example: lets take Joes RR there has to be a way the radio signal amplitude could be moved as the train moves by a series of woofers spaced 5 to 10 feet feet apart where more than one engine can be overlapped and their sound shuffled from one woofer to the next in both volume and engine rhythm and allow the illusion of trains coming and going from area to area like stereo when they move the sound from the left speaker to the right by a potentiometer but instead of fader being moved mechanically the use of on board microphones picking up the sound from each engines sound system and transmitting it to each speaker as it gets closer to one speaker it would increase and then decreases as it moves away from the last so depending on where you stand you'll hear the engine approach and then fade away as it passes on to the next area and the next area would then receive the signal and so on and electronically the speakers can be made to only broadcast the bass and not the rest of the sound the engine sound system would make the rest of the sound to help keep each engine separate from the next. They do something like this with Movies and Quadraphonic (4 way) and Octophonic (8 way) sound systems. It will take some thought and whom ever does figure it out will become rich.

Dan