Sub Mini - how do you know it is actually performing as it should?

Yes. In the app there’s an on/off toggle under settings for the room. 
 

Also, plug the Sub into a power extension cable and try it in different locations around the room (the extension cable saves you unplugging/plugging in and rebooting). Position of a Sub and the room’s acoustic characteristics can make a big difference. 
 

Try streaming something from Spotify or Amazon for a higher bandwidth data source. 

YouTube music is frequently only in stereo, and doesn’t fully exercise the Sub like your home theater setup does, using the .1 channel. Make sure that you’re getting the full use of all the channels, in order to truly ‘test’ the Sub. 

You mean this setting??

Thanks for the answers.

I am a newbie to sound systems. Don’t know anything about channels.

Only bought the Sub Mini because it was a ‘package price’, and thought it might be a bit overkill.

Next dumb question - if I sit right beside the sub mini and put my ear close, should I be able to hear ‘something’ coming out…….or is the noise just fully dispersed around the room??

You should be able to hear the sound IF it is present in the source, playing a low quality source or one with no low frequency content you may hear nothing.

The sound isn't dispersed around the room, the sub sends out sound that interacts with the room. Managing that interaction is key to getting the most benefit from the sub.

 

You mean this setting??

 

 

Yes, that’s the Sub on/off setting. But as already said, play something from Amazon, Spotify, Sonos Radio or similar (ideally in HD or higher resolution) but not as a tv audio source or from YouTube. You can also boost the Sub’s output with that Sub Level slider. 
 

Just to be sure, I feel that I should ask:   have you added the Sub Mini to the Beam, or just added it to your system?

 

You mean this setting??

 

 

Yes, that’s the Sub on/off setting. But as already said, play something from Amazon, Spotify, Sonos Radio or similar (ideally in HD or higher resolution) but not as a tv audio source or from YouTube. You can also boost the Sub’s output with that Sub Level slider. 
 

Just to be sure, I feel that I should ask:   have you added the Sub Mini to the Beam, or just added it to your system?

OK, I don’t subscribe to anything like Amazon, Spotify, etc, but managed to get Sonos Radio working, so I will try that.

I have a 2023 Samsung TV with eArc, I connected Beam to TV with HDMI/earc and it immediately started sending sound through the Beam. A noticeable difference to TV sound output.

Sub Mini arrived a couple of days later and I followed the Set Up instructions - but I don’t know if that means I added to Beam or System. System I think, but not 100% sure.

Thanks for your comments

Go to Settings, then under ‘Your System’, click on ‘Living Room’. It should list the connected speakers in that room, somewhat like this:

Go to Settings, then under ‘Your System’, click on ‘Living Room’. It should list the connected speakers in that room, somewhat like this:

 

OK, I think that is the same as the image I posted just before your post.

The definition of “my system” is not clear to a newbie like me. 

It looks like “my system” is my living room, and I have 2 products in there - my Beam and my Sub Mini. I therefore assume I connected the Sub to “my system”, not to the Beam.

Apologies for being a newbie!!

You can test the Mini Sub by muting or disconnecting it temporarily — the difference should be noticeable in low-frequency sounds (bass). Another easy way is to play a test track with prominent bass tones (many YouTube “subwoofer test” tracks exist) and listen for vibrations or rumble. Placement also matters: try moving it closer to a wall or corner to feel the bass better.
 

Really? I had no idea! I will try this

Thanks for all the answers from everyone

If, after that, you still think it’s not working, contact Sonos support who have many diagnostics utilities they can use to check things for you. 

Can someone point me to a thread/sub forum where I can start to learn a bit about the quality of audio sources? (Had a quick look around the forum, but too much info! )

So much nonsense out there. Pretty much CD quality is as good as you can hear, anything beyond that is inaudible.

Lossy formats like MP3 are more complicated and not recommended for quality sound.

Try grok.com and 

Tell me about digital audio formats