I read it again. I think I get it. Y connector with the Two RCA end going into the DCC2's L & R RCA outs and One RCA end going into the SUBWOOFER, so that the low frequencies from the DCC2's L & R would go to the powered Sub.
Then, XLR's from the DCC2's L & R to your amplifier's L & R channels.
Am I right?