Sonos does not employ digital audio enhancement settings such as stadium, concert etc. Therefore, if there is no surround track in the source material the surround speakers will be silent. You may get an occasional “bleed” through to surrounds on some stereo sources; but don’t depend on it as a regular occurrence.

You can set the surrounds to play in full stereo for music along with the soundbar and they will auto switch back to surround (movie) mode when done.

Thanks for the reply. So era100 will not work as rear speakers when the video does not have surround. Too bad. I want to have sound in al speakers 

 No speaker will make sound when you do not send sound to it, be it a Sonos or other brand.

When a source is only sending two channels of sound that is all you can get from that source.

If you  buy a device that offers a DSP that creates additional channels of sound from a two channel source then you can get sound, within the limits of the DSP,  from all connected speakers by using the DSP's output as your source.

Sonos does send sound to rear speakers with stereo sources when you are not using a TV and have the system set to “Full” though. Sonos does not allow this however on TV-sourced stereo material.

Surround sound does not mean “sound in all speakers”.  That is a frequent misnomer.   

Exactly!

If you play Spotify or Tidal stereo content, for instance, from the Sonos app, it plays through the rear speakers and sounds phenomenal. It's a feature, you can even control how it's implemented with the "ambient" vs "Full" selection in the "Music playback" section of the app, and control the volume of the rear speakers in the "Surround" section. 

But then you go to the TV and.... No rear, regardless of whether it's a concert on YouTube or you're using the Tidal app on Android TV. Kind of disappointing, TBH...

Switch to a music service that supports surround sound, or better Atmos, and you will not have to deal with only stereo sound.

Same for the TV pick a source that offers surround or Atmos and you will get great sound.

In terms of music services, Tidal offers “normal” stereo tracks as well as Atmos tracks: if I play either via the Sonos app, I get sound from the rears (even if the input is stereo) and it sounds phenomenal.

But on the TV, using the official Tidal app for Android TV….no sound from the rears. Maybe Tidal’s Android TV app doesn’t support it, it’s just weird that via the app, it’s able to send to play sound out of all speakers even when the source is stereo, but not when the source is the TV.

All I’m saying is that this feels like a missed opportunity that the “virtual surround effect” created when streaming stereo via the Sonos app can’t be replicated when the source is the TV; I’d love to be able to watch a concert or video clip on Youtube, Spotify or Tidal and get the same kind of sound I get when playing non-Atmos content via the app…

Are there any video sources that support surround or Atmos that you know of and can recommend? 

TV and streaming work very differently in Sonos. In TV mode the sound is played as presented to Sonos. EDIT: This is incorrect, see Corey's best answer above.

In streaming Stereo sources Sonos offers two surround modes, Ambient and Full where some or all of the main channel sound is passed to the surrounds.

I use Amazon Music on a Firestick with my Arc and and the Atmos sound is fantastic, I really notice when an Atmos track ends and a stereo one starts.

Sorry I don't know anything about Tidal or their TV app, maybe someone else has a suggestion, 

It often depends on the installed TV app, as well. Some of them offer multichannel sound streams, often accessed by setting options on the app, or subscription types with the streamer. Older or non-updated apps on TVs don’t offer anything other than stereo sound. 

I guess it makes sense that the Arc Ultra doesn't know what kind of audio it's receiving—whether a movie in stereo or stereo music so... I guess it's only normal it omits the rear channels. Still, it would be cool if it had the option within the app to tell it that the TV is currently playing music, so the rears could also be used in YouTube, etc.

Good point. It's a 2025 TV with Google TV, so it should be up to the task...I'll make sure the apps are they're up-to-date and tinker with the settings. On my phone, Tidal supports Atmos tracks, but perhaps the app for Android TV doesn't have the same features, I'll have to check the settings, thanks for the tip!

Certainly worth checking the TV for updates, too. I think sometimes they also update the apps. 

Hi ​@Dieguito 

Welcome to the Community!

We do, in fact, already “up-mix” all TV stereo sources to surround sound. This does not mean that you will hear all the audio that comes from the front out of the rear speakers too - some sounds will come from the rear while the majority of the sound will come from the front.

It is possible that you won’t even notice the effect depending on what is playing and the quality of what is playing, and the level will be low - it’s more to bring the soundstage forward a bit rather than to emulate true surround sound. If you place an ear close to one of the rear speakers you will hear some audio.

There is no way to adjust the effect short of adjusting the surrounds level for TV audio (Settings icon » iroom] » Surround Audio » TV Level), and there is no way to have the same audio play from the rears as from the front - the only way to do that would be to have them in a separate “room” in the app and grouped with the Arc Ultra.

I hope this helps.

That is very interesting, in several years of use I've never noticed sound from the Surrounds when playing a stereo TV source. Ambient Mode streaming music is quite obvious.

I'll have to look into this a bit more here.

I'm so disappointed, I had a Beam prior and now I have an Arc Ultra and 2 100 Era, everything was much better with the Beam.

Now I don't even have the option to have sounds from the rear speakers where I had the option to raise the volume from them prior to buying the Arc.

This is quite the letdown and unacceptable to be honest, I will probably send the Ultra back.

Hmmm….

​@Davidor 

What about your setup is not available for surround audio as listed in the link below? Let us know.

https://support.sonos.com/en-us/article/change-surround-audio-settings