No, you can leave them completely as they are right now.

It “may” be easier to set up the Arc (not ARC, which is Audio Return Channel, which the Arc uses...someone remind me to scold Sonos for this silliness) by unplugging all of your S1 devices from power first. Then, once you’ve set up the Arc, you can just plug back in your S1 devices to power, and you should be good to go, running both of them using their respective controllers. 

Thanks Bruce.  So I just download the S2 app separately and follow the instructions above, and add the Arc?

That would be my strategy, yes. It might be overly cautious, I’ll admit, but should work without issue. 

Hi Bruce.  I managed to follow the steps you set out above (almost - see below) and installed the Arc and S2 App whilst retaining all the other products on the S1 system.  Thanks very much for your advice. 

The only product I have had a problem with is the Sonos Move.  I did turn this off, but somehow it must have come back on whilst I was installing the Arc as it appeared on the S2 app.  I've removed it from that and it has reappeared on the s1 App (system).  However,  I think it must have the S2 software update on it now as it says the Move is ‘Incompatible’ based on the software.   It gives me the option to ‘Download Sonos S1 on the device but when I try this, it gets through the first 2 stages and then at the end says‘ Update Problem’.   Do I need to reset it to its factory settings and then add it back to the system?  I also looked at removing it but the option is greyed out.   

I don’t think the Move was ever S1 compatible, but I don’t own one to be sure about that.

You could try the reverse of what I suggested above, unplug all of your S2 devices (just the Arc, I think), and then factory reset the Move to see if it can be re-added to your S1 software. But I’m dubious that it will work, as I believe my memory says the Move came out after the S1/S2 split, which means it would be S2 only. 

Thanks again.  The Move is compatible with both systems Sonos confirmed here: Sonos S2 compatibility | Sonos  so I could try the reset.  Does the reset affect registration on My Sonos or will it note its been re-added??

No, a reset would not impact the registration of the device to your ‘account’. 

Thanks again Bruce, the Move is reset and back working on the S1 with the rest of the Apps.  The only issue I have left is that when I try and open the S2 app, it wont open properly and wants me to open the S1 app or set up a new system using the s2 app.  It has opened a couple of times but I don't know how.  Any thoughts?

That’s odd. Just to confirm, the only device you have that is S2 is the Arc, and everything else is S1, correct?

I don’t run a split system, so some of this remains conjecture, but I’d be awfully tempted to go back and again unplug all the S1 devices from power (or, I guess for the Move, power it down completely). Then you’ve only got the Arc on your network to deal with. Try opening the S2 app and see if it does fully open. If not, just delete the app and then reinstall a new version, making sure to ‘connect to existing system’ when given the option. Assuming the Arc has been fully set up, you should get that option. If the Arc is in a bad state, and you don’t get the ‘connect to existing system’, I’d likely factory reset the Arc and set it up again. The key thing is to get it working properly before you plug back in the S1 hardware. That means testing opening the S2 app several times just to check ;)

Once the S2 app opens and connects properly to the Arc, you should be fine in plugging back in all the S1 devices, and then opening the S1 controller to make sure they show up and function. At that point, close the S1 app, and reopen the S2 controller, and the Arc should still show up. 

If it doesn’t, then I’m clearly not understanding something, and would recommend that submit a system diagnostic , and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

There are others in this forum who do run split systems, I think, and may respond to explain if I have erred in my understanding. Just out of curiosity, what legacy devices are you running that are not S2 compatible?

I think Ive sorted it thanks Bruce, I reset the app (or something similar) when it gave me options.