. . . My question is whether it would be worthwhile (and possible) to mount the mains upside down . . . ?
Hi,
You can mount the M22 In/OnWall upside down. Once pushed in in place it will slide down and lock up just as if it was a standard installation. Install the mounting frame on the wall opening as it is needed for a normal installation; do not rotate it.

I don't think flipping the left/right speaker upside down would make any difference in sound, and having the tweeters for all three as close as possible is a good thing. Actually, having them as close to ear level as possible when seated is also a good thing. I guess I'm not sure if you can even mount these speakers upside down. Now, turning them sideways would not be good.

These are designed for mounting only in the upright position. Mounting them upside down would not allow them to lock into position.

Same with the on-walls. They can only mount in the upright position. Only the boxy speakers, the in-wall, or the in-cabinet would allow you to mount them upside down.

Cat's correct. The in/on walls need gravity to 'lock' them into position. Upside down mount and you risk them falling to the floor.
I wouldn't worry too much about the tweeter height difference. As close to the same height is the best case scenario, but most systems out there have this type of difference and sound very well. Just do the best you can within the limitations of your room and enjoy!

Hi,

I'm sorry, by mistake, I inadvertently edited the original first post of this subject.

It can be installed upside down . . . No need to rotate the frame.

Huh - I had no idea.
Now I have to go flip my I/O wall M22's just because JC says I can! Maybe I'll even like it better? Something else to tweak - but then the Axiom logo would be upside down and the ports would be catching dust. Never mind, I'll leave them like they are.

can't you flip the grill over as well, or is the pattern different? I was thinking about the dust getting in the ports as well, maybe a black breathable material could go over, but still allow for port exhaust.

The logo on my speakers is glued to the body, not on the grill covers. I betcha a hairnet might work for the worst of the dust. I could have old lady speakers!

Classy!

No, wait, they're Laverne and Shirley tribute speakers.

I gather from the responses, particularly JC's, that I can mount the units upside down, they lock in the same either way. I assume the Axiom logo can be reversed. I'm sure I can handle the port dust issue. The remaining question is whether or not this would result in a more realistic, coherent front soundstage for movies and/or for mulit-channel music? Related to this, with the center tweeter about 28" above the floor, should it be tilted up 10 degrees or so to point more at the listeners' ears?

I doubt you will notice a difference if any. When I tested my OnWall m22's against regular 22's, I had them upside down ontop of my m22's so the tweeters would be close, and did some suedo A/B testing, worked fine.

My experience is with the in-wall/on-wall VP100. I'll have to try it again. Perhaps it's the bracket I had reversed before instead.

Thanks all, I think I will just mount them all normally.

I just checked my VP100 on/in wall and it can't be mounted upside down. It doesn't fit in the bracket upside down. If you flip the bracket over, and put it in upside down, then it won't lock in.