The subwoofer and the Red Wine Audio Signature 30.2 (left and right rca outputs of the Signature) are connected with each other by using interconnects.
The RWA Sig is a stereo amplifier, it doesn't have a subwoofer output so most likely while everything above 20 Hz sound will be outputted by the Emerald speakers, while everything below 20 HZ will be heard through the subwoofer.