Several things.

1. The surround speakers connect to your Beam using a 5Ghz “hidden” channel, so you need to make sure that both the radio (wifi) is turned on on the Beam and those surround speakers, and there’s no potential for wifi interference, particularly in the 5Ghz band, although it could be any electrical device. 
2. There is no Sonos:1, either you have a pair of Sonos PLAY:1s or a pair of Sonos Ones?
3. You mentioned a router reset. It’s not clear if you had all Sonos devices unplugged while the router was being rebooted. If you haven’t done that specifically, I’d encourage it.
4. You mention that you think it’s an interaction between S2 and your router. But you haven’t told us what the router is. We can’t say yes, or no to that. There are some routers that Sonos does claim there are issues with, and have work arounds, however. All of those are posted in the FAQ area on the Sonos website, along with work arounds.

Thanks for your reply

1. Wifi is on for the (indeed) PLAY:1's as well as on the beam. Used Net analyzer to check look at the 5Ghz channel occupation. My own router stands out separately from neighbouring channels, and is centered around channel 60. Do you know where the hidden channel is? Btw also my 2.4GHz channel does not overlap with neighbouring routers.

2. You are correct. PLAY:1 indeed

3. I only unplugged the PLAY:1's following the instructions via 'Find missing products'. So unplugged after instruction, waited for next instruction, which was to switch off/on router. Then it found the speakers again but after some time they are lost again. Thus, I also switched off the router, lan switch and every wifi/wired device, restarted the router first reconnected the sonos speakers one by one and slowly switched on all other devices. Went ok for a day, then both PLAY:1's were lost again.

4. The router is an Arcadyan Experia Box V10A. Strange thing is that I am already using this for more than a year without any problems. I also installed the beam last year. The problems started just a few weeks ago and are limited only to the PLAY:1's. I also have a PLAY:3 but that one is running fine.

1. Great. So one potential item knocked off the list :)  No, I don’t know where that “hidden” channel is, but I think it follows the setting for SonosNet in the controller. Unfortunately, never have actually “looked” for it. 
2. Helpful to know, although the software in general is the same, there may be minor differences, mostly cosmetic between the two. 
3. This is troubling to me. It indicates that the most likely issue here is indeed some sort of wifi interference that is coming to knock those PLAY:1s off of the signal being created by the Beam. But, there are other potentials, too, not just that one, which is why this whole “diagnose via text” is hard. In general, the “all Sonos devices powered off during a reboot of the router” takes care of potential duplicate IP address and DNS issues that there might be. Which is why I’m leaning toward wifi interference. But, there’s always a possibility of a hardware failure in the Beam...as rare as that is, it could be happening. Might be worth it if you were to submit a system diagnostic, and call Sonos Support to discuss it. Particularly if it were within 10 minutes of the surrounds “dropping off” the network, as that would likely show up, I think, in the diagnostic. But I get that the timing might be challenging to do. At the least, do it after they’ve dropped, and it might suggest that, for instance, the Beam was overly hot, and shutting down the wifi antenna for some reason. 

   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.

4. I have exactly zero knowledge about that particular router, unfortunately. Never even heard of the company before. And because of the way the Beam proxies IP addresses from the router to the surrounds, the PLAY:3s would probably not be at all involved in this issue, since they’re connecting directly to the router, and basically ignoring (not completely, but for all practical purposes) the Beam. So if I were to guess, there’s something either interfering with that 5Ghz signal that the surround speakers are connecting to, or there’s a potential hardware failure in the Beam. I suppose it could be in the PLAY:1s, too, but it would be odd for both of them to fail simultaneously. But the diagnostic discussed in 3. would answer that, once you’ve submitted the diagnostic to them, and called in with the number of the diagnostic. 

FYI…
A speakers wireless channel is usually available here via a web browser using a device IP address:

http:///ip_address]:1400/status/proc/ath_rincon/status

See the ‘attached’ image showing the (red) circled example.

Convert the value using the ‘center frequency’ tables below:

So in the example given the speaker is using the 5Ghz WiFi channel 108

Thank you both, it appears that with your help the plot thickens.

This morning the connection with the PLAY:1s was again lost. So if followed the instructions from Ken to find the 2.4 and 5GHz channels. I only found the 2.4Ghz channel, 3, which the central channel of my router. Then, I followed the instructions to find my missing products. Immediately after reconnection, I did the channel check again and found that my beam was indeed broadcasting on 5GHz, channel 40. My router is not on that 5GHz but some neighbouring routers are, strongest at -72dB. So could be interference or indeed the beam schutting down. A few minutes later the 5Ghz channel was at 0. Does the 2.4GHz channel take over after initialization, or is the 5GHz channel used intermittendly?

From a root cause finding point of view, I like the hypothesis of the beam overheating and shutting down or interference issues causing a breakdown of the communication. They could be related even. So I will disconnect the PLAY:1s from the beam and see whether they are stable after that.

If that works, I will try to reach customer support again. A more directed support question will help, I think. They are difficult to reach the last couple of days, which was the reason why I posted my questions on this forum. Thanks a lot so far!

The home theatre master dynamically selects the best 5GHz channel for its satellites. During idle periods the satellites revert to 2.4GHz, hence the HT Channel was showing 0.

There was mention of the router’s centre channel being 3, implying that it’s possibly using a 40MHz width. In general this is a Bad Idea for 2.4GHz. Apart from anything else it’s anti-social. I’d recommend setting the width to 20MHz, picking the least congested from ch 1, 6 or 11. 

@FromEhv 

You could perhaps try putting your local router’s 5Ghz band onto channel 40 and then reboot the Beam and surrounds so that they ‘perhaps’ auto-select a different 5Ghz WiFi channel …and see if a channel change sorts the issue for you. 

It’s also worth perhaps taking a couple of diagnostic reports, both with the ‘Surrounds’ attached and immediately after they drop-out. Keep a note of the generated reference numbers and pass those onto the Support Staff - it may show if there is a lot of interference around the setup, or if there is an issue with the hardware.

Why move the router into the 36-48 band (which the HT master tends to prefer) when it’s already up in the DFS band out of the way? Sonos HT never uses the router 5GHz; it does its best to avoid it.

(Incidentally channel 60 is an odd choice for a center channel. I suspect it’s actually the AC primary.)

@ratty: Thanks for the explanation on the 5GHz question. If I use Net Analyzer to look at the width of my router's channel peak in the 2.4GHz range, it appears to be just 20MHz, although some neighbours appear to use a double width indeed. I try to keep away from my neighbouring ranges, not only for myself as well as for them. Channel 3 appears to be the most social choice in this situation. The channels 1, 6 and 11 are much more crowded.

@Ken_Griffiths. Thanks for the suggestion. I will try this.

Actually channel 3 is a poor choice. It overlaps with 1 and 6 badly, causing interference to you and to your neighbours. Partial overlaps are significantly more damaging than cooperative channel sharing.

The nominally non-overlapping choices at 2.4GHz are 1, 6 and 11. I suggest you pick the least crowded and try it out.

@ratty: Thanks for the explanation, I did not know this

Btw. I decoupled the PLAY:1s from the beam and made a stereo pair. Of course surround does not work but the connection appears stable. I will wait for a day to see how it evolves. If it remains stable then it indeed has something to do with the 5Ghz communication. Either a beam issue or indeed an interference issue. I will follow the suggestion of @Ken_Griffiths to shift my router's 5GHz channel to the "hidden" channel hoping that the beam will choose another channel. Downside might be that I will then have overlap with the neighbouring 5GHz channel. On the other side, it appears that this is the neighbour claiming 40 MHz width on 2.4GHz, which I just learned to consider as 'anti-social' anyway

If the surrounds are going AWOL when the Beam is idle it’s nothing to do with 5GHz. They’d be on 2.4GHz. Given the evident conflict between the router’s channel 3 and the neighbours I wouldn’t mind betting that there’s substantial packet loss in the idle state.

@ratty: Ok, I will also switch to channel 1 on 2.4GHz, which appears to be the least crowded for my situatio. Thanks

Pfff. Can't get it to work . First moved 2.4GHz channel to 1 (no neighbouring router!) and tried again, no stable connection. Then moved 5GHz channel to 40, still no stable connection. My PLAY:1s keep working as long as I do not install them as surround speakers for the beam…

I see that the Play Store is crowded with complaints that look very similar. Think there is a problem in the recent software version. Guess that I have to sit it out...

Did you consider power-cycling the Beam after making the network changes, just to ‘assist’ it to make any changes to its connection with the surrounds?

Can you perhaps clarify too, that you do not have any Sonos devices at all now wired to the LAN?… if you do, you will need to set the SonosNet channel to either channel 6 or 11 (whichever is least-used locally) in the App’s network settings.

How far away are the two surrounds from the Beam?

Is there anything near the Beam thats also using a WiFi, or Bluetooth, connection? A baby monitor or anything similar, as they are known to create wireless interference?

@FromEhv 

By the way, if the surround-dropout issues continue, I would not wait to see if an update fixes your problem. I have two Beams here with surrounds and I’m not seeing the issues mentioned, so it’s certainly worth submitting a system diagnostic report and speaking to the Sonos Support Staff via this LINK in the next couple of days, just in case it perhaps proves to be a faulty wireless adapter in one of the speakers, just as an example. It’s worth getting it checked and referring the Staff to this thread too, to help show them the things you have tried already.

HTH

There’s another possibility: that the router is objecting to IP lease requests/renewal for the surrounds, proxied through the Beam. Some routers misbehave, causing trouble for a system in ‘wireless’ (WiFi) mode. Sonos Support would need a system diagnostic to confirm this, or alternatively to identify packet loss and interference.

Hi,

When I power cycle the router, I also power cycle the beam. They are both connected to the same mains switch. The Sonos setup is done completely wireless. So no direct line to the router. The surrounds are ~3m away from the beam, with a direct line of sight.

The beam is close to a smart tv, router, playstation and dect phone.

How close? Less than ~50cm from a strong RF source can cause problems. 

Can the Beam be wired to the router easily? Putting the system into ‘wired’ (SonosNet) mode might be the answer. 

@ratty @Ken_Griffiths: Thanks for your help so far, I will contact customer support after the weekend and will make the diagnostics reports just before trying to restore connection, just after it is reestablished, and after losing the connection. Hope they can help me further.

@ratty I will also take along the possible IP lease/renewal router issue.

@ratty: It is within 50cm indeed. Is unavoidable because my tv set is just 50cm away from the place where my fiber connection enters my house, and connects to the modem and router. In principle, I can connect the beam to the router but did not do this to avoid the extra cable. Was starting to consider this as a last resort.

Thing is thar the setup has been like this for >1y and was working fine up till recently.

I would try the cable (don’t forget to set the SonosNet channel too, as mentioned earlier) …and maybe try the best you can to create more separation between the router and your devices. The further away, the better, in the space you do have available.

Hi, I have the answer to my question above. In July, my router (Experia Box V10a) received an update to address a safety breach in the firmware. As a result, Sonos did not work anymore. Per 27-8 the provider (KPN) provided a new firmware version that solved the issue. No cable needed!

As many Dutch user are likely using the same router type, I thought it would be good to post the solution. My advice is to make sure to run the above mentioned router at the latest firmware version.