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