Elk Voice Speaker mounting options

I hid mine in closets and have no problem hearing them. My WAF of "gadgets" on the wall or ceiling is low. She understands the smoke detectors and the front door keypad and thats about it.
I placed mine behind furniture on the floor, just in case I want to move them in the future... high enough WAF (cant see them)
About how much area can the speakers cover? I've got an open main floor that's roughly 50' x 22' - will two Elk speakers cover it?