How tall is your ceiling? What is the distance from the top of the TV to your ceiling? How far is your primary seating location from the TV?

IMO Your’s is a subjective question. Only you can make the final judgment. However, from a practical standpoint the guidelines for mounting the Arc are tried and true. In some situations it becomes impractical for any soundbar. 

Another reason to mount the Arc or any soundbar below the TV is to anchor the audio to the screen. That positioning has been the consensus for years. 

On the other hand if you are already using a soundbar above your TV, mounting an Arc in that position probably won’t dramatically change the audio experience for the worse. Depending upon other factors as mentioned by @GuitarSuperstar you may not realize the full potential of the Arc. I’d would seriously consider adding surrounds and a sub. JMO.

It may not make too much of a difference, unless perhaps playing Atmos Audio, but even in that situation there’s a slider bar to reduce the height audio channels depending on the height of the ceiling/angle-to-listening position etc. It’s probably a case of trying it and see if it suits how you like to listen to the TV & Music audio.

Personally speaking I prefer all TV/HT/Music speakers around shoulder/head height, when seated and am not a huge fan of TV’s above fireplaces, but sometimes we may have to go with what a Home environment allows. No harm in trying these things anyway, or putting up with them sometimes, if there are no easy/better alternatives.

As already stated, it’s somewhat subjective.  I think I would opt to use a Beam instead.  You could angle it down, and since atmos is simulated, I think it may actually sound a little better, although perhaps not ‘bigger’.  There is also the option of just using an amp with third party speakers that can be placed on the sides rather than above the TV.

Thanks for all your responses. In terms of the set up, I’ve put a photo below. The TV recess is about 110cm off the floor, and there’s about 80cm between the top of the recess and the ceiling (which is 2.7m high).

I do have a sub off to the left (behind Christmas tree in this photo) and will put a pair of Play 1s at the rear - I plan to use the Sonos stands. 

In terms of the room, the wall behind the sofa is 4.8m from the TV and the sofa is pretty close to that wall. The living room is about 4.5m wide. Down here in Australia we like the open plan, so the living opens up into the dining room which connects to the kitchen - all one big long room. But the living room and TV/sofa are down the end. I hope that makes sense. Can always upload a floor plan if needed. 

 @Gavin Mooney I think the Arc mounted above the TV should be fine. Don’t expect to hear the upward firing drivers when watching Dolby Atmos content because of the long distance between the TV and sofa. But you wouldn’t have been able to hear it even with the Arc mounted below the TV. Ideal seating distance to hear the height channels is 1.5 to 3 meters.

Oh that’s good news, thanks @GuitarSuperstar 

I only just got the Arc, so could swap it for a Beam (like @melvimbe suggested) under Sonos’s 100 day return policy. But the Beam looks like a pretty big step down. 

@GuitarSuperstar I read with interest “Ideal seating distance to hear the height channels is 1.5 to 3 meters.”

Is that right!? The average TV seems to be 65” these days, which is what we just bought, and if I was closer than 3m I don’t think it would be very comfortable!

Hi @Ken_Griffiths the slider you mentioned “there’s a slider bar to reduce the height audio channels” - is this in the Sonos app under the Arc speaker? 

Yes, it’s in the Sonos App under ‘Settings/System/tArc Room Name]/Height Audio’:

I love my Gen 1 Beams in smaller rooms but the one in my media room struggled to fill the space (three open plan rooms) while the Arc does so with no issues. No way I’d go back.

I have an 8-foot (2.5 m) ceiling in my living room. My Arc is about 6 feet from the ceiling. My “sweet spot” to hear the height channels the best is sitting 5-8 feet from the Arc. If I sit any further, I cannot hear the height channels anymore.

Yes, I agree that 5-8 feet is a little close for a 65” TV, but with the clarity and tiny pixel size of 4K TVs, that distance is not unusual. But at the same time, this shows the limitation of using upward firing drivers as opposed to actual ceiling speakers for a Dolby Atmos setup.

Hi all - just to round this off I thought I’d share a photo of the kit all mounted. 

The soundbar looks high, especially when sitting on the sofa, and aesthetically I’d prefer it to be below the TV, but from a sound point of view it’s pretty OK. The Arc fills the room and it doesn’t feel like the sound’s coming from the ceiling at all.