Not very effective. The ceiling fan doesn’t help either. Ideally you want a flat 8-9 ft ceiling with no obstruction.

You might consider looking at the Beam (Gen 2) instead of the Arc since the Beam doesn’t use upward firing drivers.

Thanks for the reply. I own an Arc with 2 subs and 2 Sonos Fives currently and my apartment has flat ceilings which it works well in. This picture is similar to a house that I'm considering buying I can request it be built with a flattened ceiling and the ceiling fan shifted over if that helps. It's just a tough choice since catherdral ceilings are more visually appealing but I wasn't sure how big of a detriment it would be on my sound.

I hate flat ceilings and one will likely hurt you on selling the house.

For difficult rooms a full AVR and passive speaker set is hard to beat. Feed it from a Port to get all your Sonos music into it.

My space is pretty bad too, vaulted at a 45% angle with the TV at the tall corner and the surrounds at the short one. It still sounds pretty decent, to include ATMOS. Not what you’d get from a multi-thousand AVR - speaker setup but the appearance and space taken up, plus ease of use sold me on the ARC despite the room shape issues here.

I think so too. / Thanks for the input I might have to just try to make it work. 

I get it. We’re building a house and will have vaulted ceilings and very large open concept. And the only space for a tv is over the fireplace. Hoping that the arc, sub and 2 passive surrounds in the ceiling behind and above the main seating area will be decent. Since this new house is taking forever to build, I go round and round on what to do. But this is what we’re doing so far. Good luck  on your similar journey! 

Thanks for the reply. I feel the same way going back and forth. I hope it turns out well for you.

Pay careful attention to the temperature ratings of your TV and to your Sonos when mounted over the fireplace. You do not want to toast the screen or your Sonos.

My Sony says a max of 104 F operating and 140 F storage (no power applied) so over fireplace mounting isn’t a good option.