I had a play with MConfig when I got home and under no combination I tried can I get a comms link to appear between the HD621 and Master speaker.

The other thing, which Carl has touched on, is that I noticed the Comms on the HD621 is an input, and, in legacy comms at least, this is a C5 connection, which would be to another Meridian controller or source component, not to a DSP speaker.

I’m starting to doubt whether this is possible… Does anyone actually have this working?

O/P - have you considered getting a Meridian processor, if funds allow? Something like a 568.2mm is a phenomenal processor and would add so much functionality to your system (and allow you to use your centre DSP for Trifield, and movies, for example) for not too much money these days. If money is tight, I understand, it would just be a great addition to your setup and solve this problem instantly, also.