Is it possible to have 6 Sonos speakers in one system for home theatre setup?

There are 2 concepts at work here, bonding and grouping.  Bonding is where you configure a semi-permanent bond between two speakers in stereo, or a soundbar and two surrounds, each can be with or without a Sub.  This creates a Sonos “room” containing the configured speakers all as one, with each playing the discrete channels assigned to them.

Grouping is combining individual Sonos “rooms” to play in sync.  Each room plays all channels of the signal assigned to them.  Grouping is ad-hoc, done on the fly, and not meant to be permanent.  Note, when grouping with a TV source, the grouped room will have a slight lag behind the TV audio to account for buffering.  You may or may not notice this, depending on the distance from the TV. 

When you setup a Sonos Home Theatre, like the one mentioned, (Arc, 2 Surrounds & Sub) - they usually all talk to each other over a fast ad-hoc 5Ghz wireless network and all will play in perfect lip-sync with the TV video on screen, playing surround sound audio etc.

If you then want to send the audio to other speakers around the Home, then that’s done ‘usually’ in stereo audio and is sent either wired, or wirelessly, either over the local WiFi network, or over an internal wireless network, called SonosNet - in each case where wireless is used, the HT will use its 2.4 GHz WiFi adapter. It’s a far more penetrating wireless signal than 5Ghz, which is great for sending the audio to (grouped) speakers that might be on the other-side of walls, or located on different floors, but to deal with such home networking conditions, the Sonos players involved ‘buffer’ the playing audio. The 2.4Ghz WiFi band is also not as fast as 5Ghz, but it’s benefit are it’s more robust when operating through walls etc.

The buffering involved, may cause a very slight delay of around 75ms, or less, to the playing audio, depending on network conditions …and for really poor conditions the buffer can be increased in the Sonos App. That means if you place speakers ‘grouped’ with the HT main setup, in the same physical room,  you might notice a very slight echo -  but if you place those speakers some distance away and in another room, then all will likely play fine and may appear to be in sync as you walk between rooms etc.

So the answer is ‘yes’ the TV audio can play on other Sonos speakers, or ‘rooms’, in your setup, in fact it can play on up to 32 speakers in total, but you would need rather good network conditions to do that.

I personally have no issues playing on more than a dozen speakers (up-to 5 or 6 Sonos rooms, as an example) and that’s with my ‘busy’ Home WiFi network.

I will also just add another further thing. The Sonos App has a number of tools/settings available not only to adjust buffer sizes, but there are also some slider-controls too, to help bring grouped playing speakers into perfect sync, but note when using such features you may find the audio is then slightly out of sync with the video on the TV screen, but I find these tools/features useful when listening to music and music videos playing from TV Apps - YouTube, Amazon Music videos etc.

Anyhow, I hope that information also assists to help ‘clear the mist’, a little.

Thank you for your time J & Ken. This is helpful and sheds more “light”.

To be clear, I’m definitely aware the additional Sonos speaker is not fully on the “varsity” of HT (5.1) system. That “team is set”… but I can still “piggyback” on it by “grouping” the lone speaker w/ the HT system, right?

Wife just needs to hear it (not fussy if it’s not in stereo by her), so 1 additional One SL will do the trick, right?

Thank you!

Correct.  You would group a single One with the Home Theater room.