Plantronics + Polycom.
Now together as
Hi - I'm having exactly this problem with a RealPresence Trio 8500.
"We a a problem with the speaker voice quality during a call.
If the microphone is muted the voice quality of the integrated speakers is excellent.
But if I activate the microphone the voice from the speakers is interrupted/intermittet and hard to understand..sometimes louder sometimes quieter."
That describes it exactly.
It's also reproducable with the inbuilt Audio Diagnostics tool.
Can you advise me on the what the resolution could be?