I think you’re on the correct track. The Sub, or Sub mini, connects to the Sonos Amp using a 5Ghz connection, which is more sensitive to distance and absorption than a 2.4Ghz connection. It’s entirely possible that the distance is too great for a stable connection, or that there’s enough material (wood, plaster, etc) in the way that is absorbing some amount of the signal. 
 

This will be tough to resolve.

Try moving a ONE closer to the MINI and wire the MINI to the ONE. This is not the best imaginable solution because two wireless players strapped together don’t always work well. If this scheme seems to work, you might be able to replace the ONE with a BOOST. No promises.

Another solution might be using EoP (Ethernet over Powerline). While this would be my last choice for a SONOS system, sometimes there is a miracle.

Another possibility is relocating the MINI and/or AMP slightly to a more favorable 5GHz signal location. Note that this can also be a fragile solution during parties. Humans are mostly water bags and water effectively absorbs WiFi.

Thanks Bruce. If you’re right, and I suspect you are, my next effort will be to see if I can get the amp to interface with the mini like the Sonos Ones do ( all on the same wifi signal, 2.4 ghz, on WM1). If I can’t I’ll probably return the mini. I committed to the outdoor speakers (Bose) when I bought the amp. It’s all been good ‘til now when I’m realizing that the amp is a bit more complex than the other Sonos speakers for music. 

Thanks Buzz. I actually pondered a new location for the amp. Of course it would need to be inline with the speaker wires that feed the outdoor speakers. In this case it would be in the roof adjacent to eaves near the deck speakers. That sounds like a semi nightmare to set up (probably needing a new outlet location) and a full nightmare if I ever needed to troubleshoot the amp later. I’ll probably wait to see what Sonos thinks then do some soul searching about how important the extra bass really is. First world problem?..yes. 

Buzz,  based on your idea regarding connecting a ONE with the MINI I’ve set up (on wifi) the MINI with a ONE that’s called “entry”.  Once that was all working I took the MINI out to the deck. As long as the amp and the entry “one” are both playing I’ve got the MINI bass outside. Not ideal but a possible work around. Besides, when the mini was working as a surround to the amp it seemed there was limited volume available to the mini. Maybe I just imagined that. Anyway, thanks for your thoughts.
 

Dave

A single ONE cannot be a surround speaker. And, unless you are using an HDMI-ARC connection to AMP, it cannot be the foundation of a surround system. In your lash-up as the MINI communication enhancement there is no need for the ONE to be playing anything, but it can certainly be part of a Group. In this configuration ONE’s primary function is as a wireless mesh point for MINI’s network connection.

I’ve done similar in the past and it mostly worked, but there were a few incidents requiring a reboot. This is not a recommended best practice. If this works satisfactorily for you, go for it because it’s quick, easy, and avoids a nasty rewire. BOOST is a good candidate here, but if the environment also has BOOST on the edge, I’ll note that ONE’s radio is better than BOOST’s radio.

Wrap-Up…

I called support today.  The Sonos Amp does in fact drive the Sonos mini with its own wifi signal.  The recommended maximum distance between the amp and the mini is 15’ and walls make it worse.  As a work-around I’ve added the mini to a single speaker (one) in our bedroom.  When I want to have the mini on the deck I move it from the bedroom to the deck and group the deck (amp) and the bedroom (one+mini) to play the same content.

It’s not perfect in that there will always be a one playing in the bedroom when the listener is on the deck.  Realistically I did plan to keep the mini in the bedroom during the winter months and when it was not in use.  During those times of year, 8 months here in the NW, I’d have it assigned to the bedroom anyway.

So I think Airgetlam and Buzz were right on track.  Thanks for the help.

Dave

Try my other scheme of using the ONE as a mesh point. MINI would be bonded to AMP and wired to ONE. If this works reliably there would be no need to Group the ONE -- just locate ONE cleverly. Again, no promises.