So, I'm not sure about if I understand well your point but if yes my answer is the next: In Dolby Atmos content I think it is decoded first in the layer of Atmos Renderer and after it applies the layer of TrueCinema by Sonos, for the Ray (only for a big comparation) I think for all the soundbars and all the rooms (that all people's rooms are different) it applies to have the same sound as you have in your soundbar so in this case with the Ray you can only obtain a 5.1 sound and if you have surround speakers you will have a nicely experience without the Ace and when you have the Ace it will sound equal. Now for the Ace and the Sub I think you want it for more bass or only for have the sensation of vibration in the movies like Jurassic Park or movies with similar effects but for this it can't be possible because the mode of TrueCinema is for solution the privately sound or to not disturb others so including a mode like this wouldn't be a very good, right? But if you want it try to send the sound to another "room" for example with one Era 100 and a Sub Mini or gen3/4 what you want and max all the bass volumes and I don't would recommend it really much because you will have a delay (75ms) and you would using the mode wrong so take it as a advice. :)

I do not think TrueCinema works by letting the soundbar measure anything. The soundbar emits a noise that the headphone will receive and either the headphones themselves or the soundbar processes to produce a sound profile of your room. The measurement is made by the headphone.

During TV Audio Swap, Ace connects to the respective soundbar over Wi-Fi, not Bluetooth.

I have not tried TrueCinema with all various soundbars, but as the Ray and Beam (Gen1) are not capable of playing Dolby Atmos, there will be different experiences using TrueCinema as the audio format being played is not the same across all soundbars.

I struggle with the concept behind TrueCinema. I don’t see why the room acoustics should have any bearing on what you hear through the headphones. There was a marginal improvement to the sound quality when I enabled TrueCinema, but this was only noticeable in action scenes. For majority of listening, I’d be hard pushed to tell whether TrueCinema was enabled or not. Maybe my “room acoustics” are already closely aligned to the default sound settings of Ace, but I’d argue, if Ace can sound better, then why isn’t that the default sound profile.

I don’t get the sensation during TV Audio Swap that you are not listening to headphones. Voices appear detached from the screen, so the experience will never match listening to the actual surround system which TrueCinema is trying to replicate.

With regards to your question around hybrid system with Ace and a Sub. This is not possible. Any grouped room with the soundbar is separated when you activate TV Audio Swap and the Home Theatre room is silenced.

@leo07 Whilst I am - or would like to think I am - cautious about making excessive noise and annoying the neighbours, in fact I'm looking at the Ace as a possible cost-saving and space-saving means via which to enjoy Atmos.

So then, which soundbar may I pair the Ace with in order to enjoy? Thanks ​@Mr. T for the considered response.

I think the purpose of the room acoustics replication is to make it sound as though you are listening to an Atmos system, at the sweet spot, within the specific room in which you are enjoying a movie (and/or spatial audio), rather than in some other room. The experience should be as though you have kitted your actual room with an actual 7.1.4 system. I think that's what Sonos are aiming for.

Presumably once the room acoustics measurements have been taken, TrueCinema will adjust the binaural (i.e. two-speaker/headphone configuration) encoding to account for approximately how far away each Atmos speaker would be within the room in which you are listening. If you consider that different frequencies of sound diminish to varying extents as sound travels through a space - and also the how the the ear/head/brain may interpret this differently depending on whether the sound source is in front, to the side or behind - then room acoustics (factoring in the size of the room and presumably also the room's sound absorption characteristics) are very relevant to the recreation of surround sound via binaural.

The Sonos Ace cannot know the characteristics of your room until the measurements are taken; I think that is the reason that the Ace doesn't arrive with a built-in sound profile.

C

To listen to Dolby Atmos on Ace using TV Audio Swap, you would need either Beam (Gen2), Arc or Arc Ultra, all of which are Atmos capable.

I’d hope you would be able to enjoy the audio from the soundbar, ideally with surrounds, rather than always listening on Ace.

Hopefully Sonos will release a tech blog post explaining the workings of TrueCinema.

The TV Audio Swap function has its uses. People will use it if they don’t want to disturb their neighbours as you say, or even other members in their household if listening late at night for example. I used it myself recently when my neighbour had a loud party. Sound from the party could be heard when listening on Arc Ultra, but switching to Ace with ANC eliminated the noise from the party.

There are plenty reviews from people who enjoy the TV Audio Swap function, it really comes down to personal preference on how to listen. The sound profile without TrueCinema isn’t bad. As I said, I found it difficult to determine whether TrueCinema was enabled or not when I first experimented with the feature. 

I'd not actually realised that the Sonos Beam itself offers spatial audio. (I'd thought it simply had an Atmos processor, allowing for the system to be expanded into a full Atmos system - and that the processor, coupled with the Ace headphones and the True Cinema protocol, would work some magic to deliver Atmos spatial audio via the Ace. I'd thought the Ray may be equipped similarly; so: useful conversation from the point of view as to how the Sonos systems are offering functionality).