How is an additional active subwoofer connected?
Order a so-called Y adapter from the Teufel accessories page that has a cinch plug on one side and two RCA sockets on the other. Connect the plug to the subwoofer Pre Out on the AV Receiver/amplifier and connect the mono RCA connection cable to the sockets of both subwoofers. If this cabling method is easier for you, then you can connect one subwoofer to the other as an alternative. You will need two mono RCA cables – one to connect the subwoofer Pre Out on the AV Receiver/amplifier to the left line In input of the first subwoofer, and the other to connect the left line Out output of the first subwoofer to the left line In input of the second subwoofer.