Do you seriously expect a Sub to communicate wirelessly with an Amp that is 82 feet away?

The Sub communicates over wifi on the 5Ghz band which is fast but very limited in range. Therefore the answer by Sonos tech support.

The WIFI wireless access point is only a few meters away.  If I connect the sub by ethernet cable to a range extender, the range extender connects to that same WAP wirelessly and it all works fine.  So that proves it works fine over my WIFI.  I just don’t want to use the Range Extender long term.

The Sub doesn’t communicate over WiFi. It’s designed to connect directly to its bonded master device (Amp, home theatre primary) using the private 5GHz channel put out by the master. This ensures that latency is tightly controlled, permitting shallow buffers. The alternative is a fully wired path.

Connecting via a general purpose WiFi results in a roundabout route back to the master, subject to latency spikes caused by other traffic. This can easily lead to buffer starvation and audio dropouts. 

Hi Ratty.  Many thanks for your detailed response.  I have a very sophisticated UniFi network with many WAPS running at 5GHz.  I suspect that, with a high-end network/WIFI, it would probably work fine on the latency side of things. It would be nice to be given the option to use WiFi, albeit with a caution from Sonos that it could suffer the problems you have alluded to.  My problem is my 12 Sonos AMPS are racked in AV room, connected together by cable, and where I need to place the sub isn’t near an ethernet socket.  But thanks anyway

The option to connect that way used to be available. Presumably there were sufficient reports of Sub audio failures for Sonos to take the necessary steps to detect and block such a configuration.