is too large a room no good?

I too have a large challenging room 18 X 31 with 12 ft peak open beam ceiling, tile floors over concrete, lots of glass, plus an open stair well up/down.

If possible, position the speakers along the short wall. If not, then midway (or less) and fire towards a wall, not into the room. Alas, I have to fire into the long wall.

I found big speakers (lots of radiating area) to couple best. Currently biamping Magnepan 3.5Rs with Wyred4Sound multichannel amp, plus a SVS powered sub.

Getting great sound will definitely keep you busy, but hey, it's a hobby

I used ATC SCM 20 and a sub in a room with space for a complete badminton court, hot tub and large ornamental fig tree. Approx dimensions were 50 feet by 36 feet with 11 to 18 feet vaulted ceiling. No problem at all to fill this space (but I absolutely needed the sub) and I like to listen extremely loud - everything was wood with windows along two sides...not the best of acoustics due to the reflective gymn floor.

So if you get speakers with very wide and even dispersion that play at pro SPL levels with low distortion then they will fill any space well (won't fix reverberation issues but will fill the space evenly).

Without naming names (and upsetting owners), my experience with these small ATC bookshelf speakers compared to several other brands of consumer speakers (big well known names) caused me to radically change my opinion about non pro designs with non-pro drivers. Today I would not use anything but a pro design in a large space.

I agree with Aball, I think horns are by far your best choice in a room of that size. You could come up with some other set-ups that would work, but the horns will be much more energy efficient.

Aball is correct.I heard the top JBL's he mentioned at Ears Nova only a few blocks from your door

Large rooms are great in general. Gives the speakers more room to breath and express themselves.

A big room can deliver a big sound as well, but it will generally cost more to do it than a small room. Larger speakers will be needed and more power to drive them, in general.