It is perhaps worth pointing out that the unsafe room--solid walls, no exit save one small one-- is also the absolutely worst kind of room for audio. Rooms need to exist because the bass needs to be enclosed for room support. But the best kind of room is one with lots of irregularities, openings, windows(albeit covered) and so on, so that the room modes are low Q and so that there is lots of diffusion of the room sound(after the first arrival). The kind of room that is not safe, the concrete bunker with one small door, is also an audio bumer.
TM seems to be stuck with this. But it is a bad idea and should be avoided if possible.
It is an odd situation--- people have long felt that somehow home decor was the enemy of audio, that the ideal room somehow had nothing in it but audio and was "featureless". This is however psychological only--it arises because people identify nothing else being there with attention being directed at the sound of the audio only. If you need no visual distraction, turn out the lights. But in truth, lots of other stuff there makes the sound better.
The worst thing you can do is to have a featureless empty room with hard walls and no openings.
Of course one can go to a lot of trouble and buy acoustic devices which made a facsimile of what would be a normal environment. But the whole thing is a detour on an un-necessary path.
A little damping of early reflections in addition to a normally diffusive room is the sensible way to go.
Putting things in living rooms is really not bad at all--as long as your living room is not "modern"--full of hard objects--but rather is sort of old fashioned soft comfort style.
In any case, avoid the simple flat hard walled sealed spaces--sounds lousy.