Speakers only connect to my Orbi RBR 850 at 72mbps

> I am having an interesting challenge with my home speakers and my Orbi
> 850. [...]

   Why blame the router?  Do these devices get a faster connection to
any other router?

> [...] only connect at 72 Mbps which seems to be well below the 802.11n
> or ac speeds they are respectively capable of.

   Putting my bicycle on the Autobahn wouldn't make it "capable" of the
speeds supported there.  How much speed do think is needed to cope with
a couple of audio channels?