Thanks for the response.

The codes I am using are from a Crestron module posted on the Creston "Partner Modules" page. You are totally correct that there is a set of commands for the Multi Room stuff, which used the dedicated outputs and an external amp, which I don't need, and a set for the MultiSpeaker mode, using the Surround Back speaker terminals, which is what I am trying to use.

MultiRoom On for example, is :

@MPW:2,\x0D - which works

MultiSpeakerOn is :

@MSP:2,\x0D - which doesn't

In fact all the commands work except the MultiSpeaker ones, which get a feedback of:

@\x15\x0D

Any ideas?

it is REALLY odd that the IR commands work but still there is no serial feedback. I have a similar instance where I can't control a DenonDVD player properly via serial, but I send IR command to it and get feedback via serial, happy days (I have a cable problem I can be bothered fixing, as it works well this way). It seems that the MultiSpeaker serial commands are somehow disabled in the firmware. Can this be the case?

Has anyone had any luck with the SR5500 or later models? The protocol looks the same even on the latest models.

Help!
Marc