How many speakers with Arc?

All Sonos HT products including the Arc only allow ‘bonded’ setup with two ‘matching’ surrounds only …and either one, or two, Subs. You can’t add 4 surrounds.

The Sonos HT products, like Arc, all play the front left/right and center channels. You cannot widen those by adding two additional speakers, although admittedly, that would be a ‘nice to have’ feature.

I have both an Arc and Beam HT setup here, with the two (rear) surrounds and Sub and they sound pretty good to me for both TV and music audio. The wireless setup is so convenient too.

Ken, thanks for that clarification. 
I have a live in kitchen/living space. 10m by 7 m. Do you think I’d be better ditching the arc to a smaller room and trying the 4 Sonos ones on their own with a base. Also If guess I need something to connect the TV which is a smart modern tv - so perhaps I can use Wi-Fi/Bluetooth?

I will first give you a suggestion to try with your current setup, but first I need to know a little more information about your current Sonos setup. If you can kindly consider these three questions to begin with…

• Are two of your Sonos Ones and the Sub ‘bonded’ together into one room with your Arc as a Sonos Home Theatre setup?
• Have you already set your Arc HT setup to play ‘full’ music audio on its surrounds? (Optional - but great for grouped music audio playback).
• Are the other two Sonos Ones stereo ‘paired’ together into one Sonos room aswell?

If the answer is ‘yes’ to all three questions above, then I suggest you give the following a try…

1. ‘Group’ the Sonos Arc HT TV setup with your other Sonos One stereo paired speakers. That means you will be playing a mix of all the TV channels (front and back) also through that grouped stereo pair, which in itself will broaden the audio being output, but it will clearly ‘muddy’ the HT soundstage.
2. At this point, the stereo paired audio will be delayed due to buffering over their grouped network connection.. it’s not a huge delay, usually somewhere between 30-70ms, but it’s enough to cause an audio echo in the room. 
3. For such TV stereo audio, the delay/echo can often be resolved by slowing/buffering the TV audio-out on the HT device, using the "TV Dialog Sync" slider bar in the Sonos App Arc Room/Surround Audio settings, but whilst this may work for stereo PCM stereo audio, achieving the same with Dolby Digital 5.0/5.1 surround audio, can be far more challenging, whilst trying to keep the TV video output in lip-sync. 

After ‘grouping’ the two Sonos rooms goto "Settings/System/[Arc Room Name]/TV Dialog Sync’ to adjust the ‘TV Dialog Sync’ feature and see if that perhaps works for you.

I can confirm that works. I use an Arc bonded with 2 Sonos Fives and then group in 2 Sonos Ones. 
 

There a couple of downsides which I’m sure Sonos could fix. First, I need to add the Ones group to the Arc TV group each time. Second, the TV remote controls the Arc and the Fives but not the Ones so I need the Sonos app to control the volume.  
 

I’m about to add a Sub so would welcome a seamless solution to control the 6 devices in my Sonos TV system. 

There are a few ways to control ‘group volume’ outside of the Sonos App, the three methods I tend to use most, are via Alexa ‘enabled/controlled’ groups. Another is the Soro 3rd-party App for iOS shortcuts that can be made to work with Siri. Both have a bit of a learning curve to get them setup and working.

The third option which is perhaps easier but still has a slight learning curve and is more costly is a 3rd party remote like the Logitech Harmony remote, or Harmony Hub where you can create actions to control the volume of several Sonos Rooms and control that with a physical remote or voice control.

Other options requiring an additional purchase, include iPort xPress and Senic Nuimo Hub/Click but I believe both may have been discontinued.

I tend to use the Alexa enabled groups mostly as I have Alexa installed on my Arc. If you search the threads here you will see more information on how to use those controlling groups with your Sonos ‘rooms’.

HTH

Ken many thanks for your prompt assistance. I’ll search the threads as you say. Am I correct in assuming that once I’ve grouped them all with Alexa, my TV remote can be used to change the volume on the Arc and all the Sonos speakers simultaneously ?

No not using your TV remote (unfortunately) - that will still only act on your Arc and any bonded (surround) devices… The ‘grouped’ speaker volume can be controlled though using Alexa voice.

So, just as an example, if you create an Alexa ‘enabled’ Group in the Amazon Alexa App and set the Arc in the first (controlling) section, and the third (speaker) section and then also add your ‘other’ (grouped) rooms to the third (speaker) section aswell, you can then ask Alexa (via the Arc VA) to set the group volume (using integer values) the volume will adjust both for the Arc and the Sonos products in the speaker section of the group.

An example instruction would be “Alexa, set the volume to 3” - which sets all the grouped speakers to a 30% volume level.

Thank you Ken, sounds good. 

Just recently decided to go with a Sonos setup after many years of a traditional stereo setup.   

My current setup is Arc, Sub, 2 rear One SL’s

Curious how you have the 5’s and Ones setup?  I'm assuming 2-5’s in the front?  I definitely feel the front is lacking in my current setup.    

Thanks