Andy Burns wrote:

The Logitech sounds best to me, I would have no issue having a
teams/zoom/webex call at that quality ...

Ah, many thanks for that. It's becoming clear that the problems I'm
experiencing with the sound quality are almost certainly due to my PC's
playback, my hearing, or a combination of both.

Today I'll try playing my triple-test file through my AV setup: highish-end
Marantz amp, HTPC with a good quality sound card, and decent speakers. In
view of reactions to the sound here, that's probably going to produce quite
a different result.