The One SL is compatible with the S1 app so you do not have to replace the Bridge with a Boost.

The Play:3 is compatible with the S2 app.

Here is the full list of Sonos products and whether or not they are compatible with S1, S2, or both: https://support.sonos.com/s/article/4786?language=en_US

Could Sonos or anyone on this forum please offer a means of identifying -- perhaps by serial number sets -- which One SLs are compatible with the S1 app/environment?

There is a lot of confusion/misinformation circulating about SL/S1 compatibility.

It appears that One SL units produced after around May 2020 are not compatible with S1. I learned this the hard way after buying a One SL. Through multiple setup attempts my S1 app repeatedly alerted me that the One SL will only work with S2.

This Gizmodo article reports that only pre-5/20 One SLs work with S1: https://www.gizmodo.com.au/2021/05/the-new-sonos-one-sl-is-a-reminder-that-smart-devices-have-a-short-shelf-life/

I would like to purchase one or more used SLs for my S1 Sonos environment but have not yet figured out how to identify pre-5/20 units. I’m sure a great many Sonos customers would benefit from this information. 

Beleza Tropical,
I think you may mean May 2021 (perhaps)? - I think any Sonos One SL manufactured in 2020 is/are S1 or S2 compatible. I’m not sure about any potential changes recently (not seen that)?… In any event, the date (year/month) of device manufacture is shown on the bottom of the speaker, near the start of the serial number.

Based on the message below from Sonos, it’s my understanding that since May 25 it is not possible to add an SL to an S1 system regardless of when the SL was manufactured.

One SL products registered from May 25 will only run on S2

In 2020 when we introduced our new operating software S2, we committed to supporting customers’ older products on the legacy software we now call S1. Those products still work today as they did more than a year ago, and we continue to keep them updated with bug fixes and security patches. 

One of the limitations we were clear about was that products launched after June 2020 would only be available on the S2 app. In May, we’re releasing an update to the Sonos One SL that reduces waste, improves recyclability, and delivers efficiencies in power consumption. While there are no new feature benefits that justify releasing it as a generational update, some hardware and software changes mean that customers will no longer be able to add One SL to an S1 system. Only new or unregistered One SLs will be incompatible with S1. This change will not impact One SL products that are already integrated into S1 systems.

What does this mean?

Starting May 25, new or unregistered One SL products cannot be added to an S1 system 
Any One SL currently on an S2 system cannot be downgraded to S1
One SL products running S1 firmware in an existing S1 system are not affected.

@ Early Rejector, Thanks for sharing that. Is it possible that One SLs registered before May (2021?) and used with an S1 system could be added to a different S1 system? (E.g. if I bought such an SL could I add it to my S1 system?) Or, can they only ever be used as S1 devices with their pre-June systems/owners? 
 

@ Ken_Griffiths, I don’t see any manufacture date on the bottom of mine. “2012” is part of my SN, but that’s clearly not the year of manufacture.

‘2012" …I did mention it shows (Year/Month) … so I’m thinking that might be December 2020, perhaps?

Note you cannot create a ‘new’ S1 system with an S2 compatible product and I think to create one with an S1 only product, you may need to remove the S2 controller app from the setup device - if you perhaps want to also keep those things in mind aswelI?

I guess it’s a case that these things are also subject to change with each new update of the Sonos software, firmware, or hardware too.

@early rejecter I’m attempting to add a One SL to my existing S1 network, with Sonos Connect. I have never used the S2 app. I don’t know whether the prior owner had my SL configured with an S1 or S2 system, in case that turns out to matter. (Since Sonos no longer allows downgrading devices from S2 to S1.) In any case, I remain unclear whether an S1-configured One SL can move to a different S1 network.

Thanks, @Ken_Griffiths. If that’s right, my SL is plausibly compatible with S1, independent of whether that’s actually permitted by Sonos.

So have you cabled the One SL to your main router, factory reset it and waited until you see the flashing green status LED and and than tried to add it to the ‘existing’ S1 App setup using ‘Add Product’ in “Settings/System”? 

@Ken_Griffiths Yes. I tried this several times. In the end the S1 app tells me the One SL cannot join an S1 network.

The person who sold me my device says it was set up with the latest Sonos app (ie S2)

My experience seems to confirm that a One SL may no longer be changed by user from S2 to S1. However, still looking for a way.

Also, remains unknown whether an “S1 SL” could be moved to a new S1 network.

As far as I’m aware, if you factory reset that Sonos One SL, unless it was sold in the last couple of months, it should be able to be added to an S1 system. But you do have to factory reset it, if you just try to add it without the factory reset,  it will fail. 

Thanks for this suggestion. I followed the factory reset procedure mutile times. Whatever the barrier, that’s not it. 

And just to clarify, you don’t have an S2 Controller App on your mobile that you are using for the setup? - Can I also ask what operating system and version is installed on your mobile device?

No S2 controller on my mobile used for setup. S1 version 11.2.9 on my IOS phone with 14.4.2.

A One SL cannot be added to an S1 system since May 25 of this year regardless of manufacture date. It hasn’t yet been determined whether using the Transfer Ownership function can be used to move an SL from one S1 system to another, but doing a factory reset will definitely make it impossible as it will have to be newly registered at that point. I suspect that even Transfer Ownership won’t work though given Sonos’s reference to “existing S1 system” not being affected by the change.

Beleza Tropical,

Well that really has surprised me. The only thing I can add …and would have tried myself is, I would have certainly wired it direct to the router, maybe turned off ‘Private Address’ on the iPhone network connection properties too, or perhaps used an earlier iOS device with iOS v12.5.3 installed,  as that worked for me to downgrade a speaker last time (albeit I downgraded a Play:1 speaker) …I had to remove the S2 App in my case, but I guess things may have altered in the recent updates.

I think if you have tried wiring the One SL etc; you should contact Sonos Support to see if they can assist you, particularly as you have bought the speaker in good faith and believed it would connect to your S1 HH and see if they can perhaps assist you to sort it.

To my knowledge, that’s only if the Sonos One SL was created in the last couple of months, older Sonos Ones should still have the capability.

Would be nice if on Monday, we could get confirmation from a Sonos rep. 

They don’t unfortunately — see the letter from Sonos that I posted earlier in the thread; it says that “new or unregistered” One SLs can no longer be added to S1 systems. Only SLs that are currently registered to an S1 system are unaffected.

My decision to purchase a One SL was informed by this Sonos speaker comparison chart posted on the Sonos community forum and allegedly vetted by Sonos. 

Looking at the link above and the comparison chart, it was posted a while back and in fairness to its author, we all know that with some older forum posts that their information/content may be superseded by newer posts, like we see mentioned much more recently by Sonos Staff and copied to a post earlier in this thread.

I think it’s reasonably clear in any event, that the One SL speaker was purchased with an honest belief it was/is compatible with an existing S1 setup. The next step must be to contact Sonos Support and seek clarification on the matter and see if they are perhaps able to assist in some way to resolve the issue.

Is there a link to where Sonos posted this? When I google the message I only get quotes, like the one above. It looks like this news was not very openly communicated.

As I read it only One SL’s are affected by this, probably coinciding with the new One SL (Gen 2). Though something like this can be expected any time soon, when the One gets to Gen 3 (to keep up with the One SL.

I can see why Sonos is trying to push people off S1 and personally I’m not affected by this. But I do think messages like this should be communicated very openly, maybe even months in advance. Sonos should have learned from the poor way they communicated S1/S2 in the past and try not to surprise people, especially on this subject. Even more so since it also can affect owners that until may 25 could switch their One SL’s between S1 and S2 systems and now can’t anymore.

I believe the info was only distributed to dealers — I haven’t seen any public notice from Sonos. I agree that it should’ve been announced more widely, and earlier, as I imagine Beleza Tropical isn’t the only one finding him or herself in this situation.

Note that this “new” One SL is not a new generation; the notice posted above indicates that the changes do not warrant a generational update.

Hi everyone,

Let me try to clarify things a bit here. 

Basically, if a One SL is upgraded to S2 it is unable to be added back to any existing S1 household. If a unit with a series ID of A100 is already on S1 then you can still use it as you do today. New One SL units with a series ID of A200 will be incompatible with S1 systems out of the box. Any newly purchased Sonos One SL units that haven’t been registered to an S1 household before May 25th 2021 will only be compatible with S2, regardless of manufacture date or series ID.

If I factory reset my One SL, can I add it back to an S1 system?

If your One SL was running the S1 firmware before a factory reset occurred, you will be able to add it back to your S1 system. In the event you upgraded it to the S2 firmware, it would not be able to be re-added to S1 after performing a factory reset.
 

If I purchase an older One SL, can it be added to my S1 system?

No. The changes being implemented will be occurring through the cloud, and make One SL compatible with S2 only. If you have a One SL on an existing S1 system, you can continue to use it as you do today while receiving periodic S1 updates. If that One SL were to be upgraded to the S2 firmware, it would not be able to downgrade back to your S1 system.

The “Transfer Ownership” function doesn’t transfer the units from one household to another, it simply allows you to change the registered email address assigned to that particular system. You can do this without affecting which version the One SL is on.

We’re taking all feedback on this very seriously, and I’ve passed it on to the team responsible for this change.

Thanks James, that’s all very helpful! In reference to the above, does that mean that if the second-hand One SL had been running S1 firmware before it was resold it could’ve been added to the new owner’s S1 system after a factory reset, or can it only be re-added as an S1 unit to the original system, and would have to be added as an S2 in a new owner’s system?

Thanks again, especially for clarifying the Transfer Ownership function.