Not a very good idea in my opinion.   Part of the Arc’s functionality is to bounce atmos audio off the ceiling, and it can’t do that well being mounted so close the ceiling, and the ceiling at an angle.    The Arc also bounces audio off the walls, so placement isn’t ideal for that either.

The other issue you have to deal with is the Arc needs to be directly wired to an HDMI-ARC/eARC source, which few projectors are capable of, and you’re wiring across the room. If it were me, I would probably instead go with a much simpler sound system, maybe use a Sonos Amp with passive speakers.  You still would need to deal with HDMI-ARC connection (or optical), but the amp could be placed close to your projector with speaker wire going to speakers near the screen.

Tks a lot Danny,

for the sound we use a chromecast connected to the projector which sends the sound back to a play5. Then we use the play 5 input source to broadcast to other speakers. This is working really well now. I admit that your opinion suddenly scares me because we have already ordered the Arc ... maybe a mistake on our part then?
 

If your routing the audio through a play5 (and the audio delay isn’t bothering you) then you’re only getting stereo at the most, no surround sound or atmos.   It would make more sense to mount a pair of Ones on the wall then an Arc  It would sound better and cost less.

Tks a lot.

With Sonos v1 i did nt have any audio delay. Now with sonos v2 i Have a delay and i thought that with Arc perhaps the problem will not continue. Do you know why I have this delay ?

So I will try to cancel my order and to order two play 1 in place of this order.

Tks a lots for your answers !!!