The source needs to be encoded in a surround format and some sources are not.  Check the format on the Now Playing screen in the Sonos app.  If you don’t see Dolby Digital 5.1 or Atmos, then you aren’t getting surround, and the effects will be minimal, if any at all. 

This will be the same for most systems, not just Sonos. I believe that some sound processors have a “sports” mode which processes the audio and injects boosted crowd noise, but that’s not a part of the actual broadcast program. 

Thanks for your comment.

The Now Playing screen in the App says HDMI. How do I change it to Dolby Digital 5.1 or Atmos, please?

You need the source to be DD 5.1 or Atmos.  THere’s no way to change the source material if it isn’t already in 5.1 or Atmos. 

By “source”, do you mean TV? My Sonos setup is connected to a 2024 Samsung OLED which supports both 5.1 and Atmos.

I’m guessing the problem is with the TV then?

Thanks for helping btw

Likely not the TV but the incoming program.

You may be able to see more info on the format you are watching from the TV’s diagnostics screens.

Even if you see 5.1 or Atmos on the Sonos screen what you may hear can be disappointing if the producer did not fully use the additional channels.

No, as stated by @Stanley_4 the source is the media itself.  If it is not broadcast/streamed in a surround format, then you aren’t going to get surround.  Most talk shows, some sports, and many older shows are in stereo only, depending on your location and/or the capabilities of your provider/streaming service.  

Thanks Stanley,

I think you might be right. Sport on BBC has no surround while everything’s working on Sky Sports channels.

Something I didn’t realise but at least my speakers and TV are probably working as they should.

I appreciate your help.

Thanks for your help and patience too jgatie. This is a steep learning curve for me so much appreciated.

Your soundbar will adjust according to the programming it receives. So for example currently the football on ITV1 (terrestrial not ITVX) is showing Dolby MAT 2.0 on the Sonos app, which is nothing to do with the TV or Arc - that’s what the broadcast sound format is. The sound is coming mostly from the Arc, not the surrounds, but that’s the sound format. If it was in Dolby, it would be very different (but even then it would only be in the surrounds when the broadcast content has anything going on in the surrounds).

And just to say, the BBC iPlayer and ITVX tend to broadcast in different sound formats to terrestrial, so if for example the iPlayer isn’t sounding good, switch to BBC terrestrial which is often better. 
 

On the BBC in the uk, you need the HD channels - 101, 102 etc. Even then a lot of stuff is only 2-channel. 

Yes, sorry I forget some people still watch in SD. Weirdos.