The Denon CEOL N12 DAB has a pre-amplified subwoofer output, so you can connect a powered active subwoofer. For satellite speakers, check whether they are passive (to be connected directly to the speaker outputs) or active (with built-in amplification). This Denon system provides 2x 65W amplification for passive speakers, so you can connect passive satellite speakers directly to the speaker outputs. If your Harman Kardon satellites are passive, you can connect them to this Denon system. The powered subwoofer can be connected via the pre-out subwoofer output, usually RCA (cinch). A mini-jack connection is not provided directly on this system, but a mini-jack to RCA adapter could be used for the subwoofer if required. In short, you can connect your powered subwoofer via the RCA subwoofer output and your passive satellites directly to the Denon CEOL N12 DAB speaker outputs.

Another quick question: what is the purpose of the subwoofer cable connected with cinch (purple) and the cable with mini jack? the 2 are connected...