That would make sense as the Input would be Master comms, whilst the output of the speaker would be Slave comms (there is a slight difference!)

The input has to be two-way (i.e. to/from the DSP speaker) as they can send remote commands back to the processor (or in this case the HD621).

All inter-source communications must be using Master comms and it is only once it gets to a DSP speaker that it becomes Slave comms.

As an aside, I've always had problems getting a D1500 to work without any other DSP speakers in the system as there is nothing to give it a slave signal.

Sounds like we have a working solution...

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200.2HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5200HC, DSP33
Spare: MCD, 100 Series, 200 Series, 500 Series, F80s, C15s.