I would expect that the 5Ghz signal is being blocked/ameliorated by things in between the two devices, so I’d try first the simplest thing, by wiring both devices to the router, and ‘force’ the signal to travel that way. 

Since I consider the ‘bonded’ signal not to be SonosNet, even though Sonos appears to call it that, I’d likely try, at least, to put a BOOST halfway between the two, or perhaps a normal Sonos speaker, although my expectations would be rather low for that possibility. To my knowledge, ‘bonded’ signals are *not* as simple as SonosNet, and *may* act differently. 

Thanks for answering the call Bruce, when I called Sonos I asked if the Boost or the Bridge would help, their answer was no, it would help if the Amp was having issue connecting to the network but putting the Bridge “in between” the Amp and the Sub would not repeat the Sonos Net signal from the Amp to the Sub.  

I wish I could just plug in the Sub, the speakers are on the lanai, I am sure the hurricane glass between the Amp and the Sub is causing the issue.  Since it is a concrete home, getting a wire to the sub spot is going to be a tough sell.  I am going to prove this theory when we return with a long network cable to show this is the answer but a surface mount box on t a brand new home may not fly.

 Is it a good idea to call the peer to peer 5GHz wireless communication between a soundbar and a sub / surrounds SonosNet?  I thought SonosNet was totally different.  Isn’t SonosNet a WiFi network created when a Sonos device is plugged into the router.  Then other Sonos devices can connect wirelessly to SonosNet.  When you “bond” a sub / surround to a soundbar should that also be called SonosNet?  Probably not.

Airgetlam:  Would the “bond” between the soundbar and sub be broken if the sub looses connection to the home network?

It would be nice if Sonos came up with reasonable names for the different things Sonos uses/does and then put them in the support section as a glossary.

I can’t recall seeing an official name for the 5 gHz link but it sure isn’t SonosNet v1 or v2.

I’ve been ‘told’ sometime that engineers at Sonos call the 5Ghz connection between bonded speakers ‘SonosNet’, which is troublesome for OCD me, since it obviously doesn’t act in the same way as ‘real’ SonosNet does, as evidenced by the data received by @ShoeboxBob , our OP. And, as I suggested, I’m not overly surprised, as that is what I suspected. 
 

@MoPac , I’m not sure I really understand your question. The way I understand it, the ‘bond’ between two speakers (which is not stereo pairing, just surrounds or Sub connections) is across that ‘hidden’ 5Ghz connection, normally. SonosNet, I think (lots of caveats, I’m not a Sonos engineer, nor do I play an engineer on TV) runs across a 2.4 GHz channel, and connects Sonos speakers (that can) in a normal WiFi-ish way. Just parallel to your normal WiFi channel, which is why it can be affected by WiFi interference. I think, if you connect each device via Ethernet cable, they’ll default (via a lowest cost analysis connection) through the router…which can potentially add a slight processing delay for networking, which is why that hidden 5Ghz connection is preferred.

Or, I could be insane. It certainly fits all the facts as I know them, but I am not a real network engineer, nor do I work for Sonos. Just years and years of reading (and sometime responding) here, along with other knowledge based on working on both mobile and PC games in another life. I think what I’m saying is don’t assume what I say is gospel, always test to see if it works for you. 

Airgetlam:

 I was just wondering why some report their sub or surrounds might drop out occasionally.  The question was…. In a bonded HT setup do all the bonded speakers ( Sub & Surrounds ) also have to also stay connected to the home WiFi?  If for some odd reason a sub or surround, due to placement, looses connection to the home WiFi will it also go silent even though bonded to the soundbar?