Wireless surround speakers use a direct, private 5GHz link to their soundbar. The surround speakers will request an IP address from the router. Routers will log and report this in various ways. During initial setup the surrounds might use WiFi briefly and make the router assume that the speakers are its wireless clients -- and there may be some WiFi traffic if the soundbar is shut down. If your router logs wireless traffic, there will be very little, if any, between the router and the wireless surrounds.

OK, so it sounds like the two speakers are likely the two items in my router config that I can’t seem to identify… even though the IP addresses don’t match. I wondered if they created their own private network, which might be why the IP addresses are different. I’ll try a few quick tests to see for sure if I can match those together. Spent a good part of the day trying to figure out what all the unknown devices are on my network. Almost got ‘em all now. Thanks for your help!

Go to Settings → System → About My System. Here you can view IP and MAC addresses.