They are more-a-less intended to be in an upright position but you could probably get away with as much as a 45 deg tilt towards the listening area I would think. They're not intended to mount flat on a ceiling....it's a shame you can't do something about the wiring, maybe extend it with some flat wire to the sides or backwall if you can't fish the wire through the ceiling.

Half of communication is listening. You can't listen with your mouth.