The use by Sonos of a dedicated 5Ghz link between Amp/soundbar and Sub/surrounds is basic Somnos knowledge. “Sonos led me to believe” this link worked with normal wifi seems an overstatement to me.

Other set ups, like the one you want to try, are possible but not recommended by Sonos. That means they are probably not "bulletproof".

I have to disagree that the use of the proprietary 5ghz connection between Amp and Sub is common knowledge.  AFAIK it’s not stated in any of their promotional materials, and it’s learned from message boards like this typically when a problem arises (which seems to happen often to folks doing centralized Amp deployments for whole home audio)

Sonos markets the Amp as a turn key way to achieve whole-home audio with centralized amplifiers and passive architectural speakers.  If their proprietary 5ghz link is the only form of wireless connectivity between an Amp and connected Sub..  it should be stated clear as day.  It should also be crystal clear that ethernet connectivity is a suitable workaround when the 5ghz connection is not viable so the integrator/homeowner can plan accordingly.  Sonos dropped the ball big time on this IMO.

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I don’t have high confidence that this will be satisfactory, but an EoP (Ethernet over Powerline) link might work for SUB. It’s best not to allow the EoP adapters to share an outlet with a high end surge suppressor.

I would personally choose to wire the Amp and Sub to the same switch (or router) on the LAN and would disable the WiFi adapters, as mentioned. That would be my choice given the distance between the master and slave device in the setup. 

For future installations, my own choice would be to put the Amp and Sub in the same ‘physical’ room and run the Amp either wireless, or wired, back to the router, but leave the sub and Amp to communicate over their 5Ghz ad-hoc wireless connection.

My setup is 2 Amps in the basement in a rack, with a Soundbar in one room and a Sub in another room out of wireless range of the Amps. The Amps are hardwired to 2 sets of OEM speakers. So speakers and Sub in one room and Soundbar and surrounds in another room.

All worked fine until the Soundbar (hardwired to ethernet) in room 1 died. No light, nothing. At the same time, the Sub in room 2 stopped working.

I called Sonos and the technician confirmed that there is an “issue” with Sonos Amp communicating with Sonos Sub over the home wireless network and you need at least one other Sonos piece of kit hardwired to the ethernet in wireless range of the Sub for the Sub to talk to the Amp. The technician admitted that there is nothing to say this on the website.

So in effect, Sonos has tied me in to buying another Sonos soundbar whether I like it or not if I want to continue using my Sub with the speakers in an adjacent room to that in which the soundbar is located.

I have suggested maybe Sonos could provide me with a £99 Boost FOC to get round the issue but haven’t heard back yet.

If you’re choosing to not get another soundbar, then why not just wire one of the surrounds you mention instead? …as I assume you will be using those speakers now, either standalone, or as a stereo pair.

If using a pair I would wire the left surround. 

I don’t understand your question, @Ken_Griffiths.

What surround speakers do you mean? I have OEM (Artcoustic) surround speakers hard-wired to the Amp in the rack in the basement. What are you suggesting I wire them to?

Apologies if I am being thick!

Ah sorry @the bouscy …I clearly misread your post, I didn’t realise the Amp was ‘bonded’ to the faulty soundbar, I (somehow) thought you were using Sonos speakers as surrounds with that HT device, it’s just my mistake.