how big a speaker can you put in an 11 x 11 room?

Depends how big the door is.

I have responded in another thread on the same issue in that I am a big fan of small speakers(either small towers or bookshelf speakers on stands) + subwoofer in a small room. A large speaker in a small room often sounds like crap most of the time. Having said that, I have seen a guy having the Marten Coltrane floorstanders in a 9'x13'x8' room which is an exceptional case. However, that room has got some real serious treatments and planning gone into it as all the wall surfaces which include the ceiling have been treated.

Dgad's advice may only come in useful if the speakers are meant to cater for a strong 100,000 crowd of a large rock concert.

Some speakers are designed to be listened to at a greater distance than other speakers . Your question does not have a one size fits all answer...pun intended !

Happy Tunes .

Will you be able to place the speakers properly away from the walls and still sit far enough away from them for the separate drivers to cohere? You can't sit but so close to physically large multi-driver systems and not hear the individual drivers as individuals drivers.

I'm not even going to mention that your room is a square and the problems that will present for smooth bass response.

I agree the main issue is how far you can get from the walls. I have a small room myself, and one set of rear-ported speakers (Soliloquy 5.3i) clearly overwhelmed it. A much larger rear-ported speaker does a lot better! (Usher CP 6311). So I guess it's the speaker design too. Go for front ported if you can