Originally Posted by SeaNile
Not quite sure I can hang those from the ceiling!
Yeah, not sure I'd be comfortable hanging something that could kill people if it fell on them, although I see it in commercial venues.
Ideally, ceiling and surrounds should match as much as possible, for the best imaging.
High efficiency, wide dispersion characteristics, and ability to angle toward the MLP are also ideal.
I'd recommend any one of these to go with JTR mains:
1) JTR S8s
2) Seaton Sparks
3) Reaction Audio CX-8s
4) DIY Sound Group Volts or Concentric 8s (C8s if you want to minimize the DIY portion)
All these are close enough and capable enough that after running room correction, you will have a good match.
Some people like to run bigger speakers as surrounds, but these concentric models have better dispersion characteristics and give you the ability to use all matching speakers for surrounds + ceiling speakers.
For practical reasons, you may want speakers that can actually be mounted inside the ceiling. This is less ideal acoustically, but you can still do well. I think JBL makes some high efficiency, high output ceiling speakers. It will usually sound better to go with one that provides an enclosure inside the ceiling, but that's not a requirement.