Fran

Your set up sounds interesting but I don't understand something. Would you please explain?
Are your 2 12" speakers in mono coming out of one output and is you sub-woofer coming out of the other output making the two channels stereo?

What do you mean when you say you're sending the mix to a sum out instead of the sub out.
It sounds like you have a separate slider for the 2 12" speakers and one for the subwoofer.

Thanks.

Peter