As you perhaps realise, one set of speakers would need to be factory reset and then set up afresh as a ‘new system’ while the other set is temporarily powered off.

As for using a single phone/controller for both systems it’s not very practical. A controller that’s associated with both systems will pick one at random whenever the app starts. There’s no way to steer it to one system or the other.

Take it from me that the process of force-quitting the app, restarting it, force-quitting it, restarting it, and so forth until it eventually picks the system you want can get tiresome pretty fast. You’d really need to dedicate a controller to each system.

> There’s no way to steer it to one system or the other.

This was the part where I was hoping the Sonos phone app would be helpful, allowing the user two choose between System A and System B, then allowing control of the speakers in that system.

So thanks for confirming that it’s not possible.

> one set of speakers would need to be factory reset and then set up afresh as a ‘new system’

yeah, I was aware that I’d need to factory reset the speakers that I want to move from System A to System B...

> while the other set is temporarily powered off.

...but I wasn’t aware of this!  

So, do I need to power off ALL speakers that are to remain in System A before factory resetting the System B speakers?

in other words, when I factory reset, it won’t give me the option of “Add to existing System A, or Add to new system?”

You’d need to reset a controller and choose ‘new system’ to set up system B. Of late it’s been recommended to temporarily power off the system A units to prevent the controller ‘helpfully’ trying to combine everything into one system.

Some third party apps can handle multiple Sonos households on the same network without issue. SonoPad/SonoPhone for iOS presents a merged view, my Windows app prompts on startup for which household.

Both a lot easier to use in this case than the official app which requires “forgetting system” / restart to switch.

It’s worth noting that third party controller apps don’t feature options to setup/configure Sonos systems.  

Nor do the official Desktop apps from Sonos.

Hardly relevant, as the OP’s question is about phone apps. 

Also how often do people need to setup/config their systems anyway? Clearly not often, else it wouldn’t have been deleted from the Desktop apps. Though that’s only part of the reason 3rd party apps don’t do it.

How about using two routers or a router with two LAN connections work for this? Hook one Sonos to each and then connect the controller to the WiFi of the Sonos you want to control. Only issue would be dual-homing any music library to both LANs.

I followed this - turned off all my System A units, and as you said, when I powered on my factory reset System B product, I was able to add this product to a new Sonos system on the same wifi network.

Thanks!

Thanks for this suggestion Stanley.   This might also have worked, had I not already tried ratty’s approach, and luckily had an old iPhone available to control System B.

What now seems apparent to me is that the official Sonos apps should easily allow selecting which System you’d like to control in a separate menu option.

Yeah, I mostly use my iPhone app to control my Sonos.   So although the third party apps might help to handle selecting different Systems,  I don’t want to have to Forget System / Restart each time I want to make a system change.

Not going to happen IMHO. The percentage of users who intentionally create multiple S2 systems on their network must be absolutely minuscule. (Much smaller than the fraction who create two systems unintentionally.)

Per my analytics, around 20% of users have two Sonos Households on their networks. I cannot tell if they are S1+S2 or some other combination though, but I agree that multiple S2 systems deliberately on the same network seems unlikely.