I’d say in most cases using one would be enough but there are a few times using two could be beneficial. I’ve tried both one above and two (one above one below) and both worked great however for the 56” DLP I was using at the time one above was more than enough.
The two cases I find doubling them up useful is on a larger screen if you can clearly hear that the center is either above or below the screen. Having one above and below centers the sound I the middle of the screen. The other case is when even on a smaller screen you can’t get the tweeter of a single M22 near the same horizontal plane as the tweeters on the mains. Again centering the image with one above and below can keep the center from sounding like it’s higher or lower than the mains.
Also Fred is presently using 2 M2s one above the other below his screen with M80 mains so that might also be and option.
What speakers are you getting for mains?
