Well, Phelonious - glass itself ain't so bad. In fact the BBC today builds entire recording studios out of it. Yep, they do. Whatever treatments they require, they put in the ceiling or floor. Speakers from Crystal Cable, Perfect8, Waterfall and others are made out of glass. The right glass can be a terrific material for sound. Very large relatively thin glass panels will of clourse flex and leak a lot of bass. The Munich show traditionally suffers that. In my room however we're talking far smaller double-paned heavily framed French doors which are all angled relative to the listening position. Then we've got a two-storey ceiling above the speakers into an open 30sqm loft with a compound-angled ceiling. There's no wall behind the seats until you get into the open floor-plan kitchen...
I've tried overdamped rooms. I've even had corner and sidewall traps. Guess what? They sucked all the life out of the sound. I made them available for free. Couldn't give 'em away -
What
is important at least in my experience is path-length equality between speakers and seat down to a millimeter; perfectly symmetrical toe-in (or not); sufficient distance for early sidewall reflections to arrive outside where the ear/brain sums direct and reflected sound to smear; preferably higher ceilings or cross beams on lower ceilings for some break-up.
Just as important is not to have too much speaker for the room.
Rear-firing ports close to front-wall corners become big pressure zones for LF which damps HF and causes booming which sound like room modes until you plug the ports and they, poof, disappear (or reduce significantly). Each room's decay behaviour is its signature and apparent already in your own foot fall and by listening to your own voice and that of others. If they sound natural, intelligible at low levels... then the acoustics aren't bad as long as you're not using a speaker which overloads the room. Hence my
general preference for two-ways, with perhaps some very mild active sub assist below 40Hz.
Your type of comment reminds me of a forum whose owner predicts the sound of installations purely on their photos. He then describes everything that's wrong and what the sound is like. If I could do that, I wouldn't have to do any listening at all. Manufacturers would send me photos of their equipment in their room and presto. Or, they could just send me the measurements. Again, no equipment necessary. Am I jesting? Only half.
I don't expect you to believe me by the way. I will simply add this. I've gone to many CES shows as a manufacturer to set up rooms. Before that I was a sales manager who visited dealers across the US. As a reviewer I've covered numerous shows for the last 12 years to hear a lot of stuff in a lot of different spaces - from atrocious to stunning as this and last year's Vox Olympian installation by Living Voice. I think I have a fairly decent take on what's possible. Using that as a reference, I find my room a most suitable tool for the job. A particularly
bad listening space? You're convinced. So be it -