In a conversation with Ian a little while back I found out that the M3 in-ceiling speakers were not totally transparent. To create a speaker flush with the ceiling required the speaker to be recessed behind the flange, and apparently, this gives enough clues for us to know where the sound is coming from. (note this is probably true for all in-ceiling speakers)
My first reaction was dismay … But thinking about it more I decided that in most cases you really should not care.
First let’s look at why anyone would care. If you are in the sweet spot of a decent stereo setup ... instruments and vocals should be coming from where the recording engineer placed them and not the obvious source (the speaker). Now with a conventional set of speakers you’d sit between them and typically somewhere around the same distance from the speakers as they are from each other to get this sound stage. Get too far left, right, close, or far and the stage will get muddied or collapse.
Now let us think for a minute about ceiling speakers. First off they are already compromised as they are … wait for it… on the ceiling. I’m really not that concerned with the sound stage coming from above as I am about not being in the same plane as the speakers are firing. Very rarely are you standing right below them. So right off the bat the speakers are not firing at you as they would if a pair was sitting on the floor. Next if one thinks about how far from the speakers our ears are … we are much closer to the ceiling than we would typically be from a stereo setup on the floor. For example if the ceiling speakers were 10’ apart and our ears were at 5’ the we’d need a 14+’ ceiling while standing directly below them to be in the middle of the sweet spot. If your ceiling is 8’ high you might be hard pressed to find a sweet spot if you were standing. So even if a ceiling speaker could image well in most cases you might not be able to take advantage of it …
Now, “does it matter?”
For background music, in your dinning room, hallway, or anywhere else your not going to be sitting consciously listening for the stage it’s not going to matter.
As a 5.1 or 7.1 surround speakers they are a poor substitute for any of the QS speakers (which give a field of sound you can not localize) but if aesthetics are an overriding factor it will probably do an ok job at giving you the surround effects. One might note that even if you could localize where it came from, while the movie is playing your concentration is elsewhere.
In an ATMOS system you’d like your speakers to image smoothly as objects fly around you but you are also limited by your ceiling height. So if you have high ceiling you might consider using the M3 in-wall or on-wall versions (which can be transparent). But for most of us with ceilings 9’ and under the in-ceilings would probably not be any worse.
The only other case I can think of is that these are your main speakers … in that case you ether don’t care about imaging or you made a very poor choice.
Bottom line ... if your creating a ATMOS theater and have 11' ceiling you might steer away from the in-ceilings. In all other cases they are probably be just fine.