Hi guys, I’m an absolute lender for systems but I bought a modern radio and subwoofer for my Audi 80 B4. Radio installed yesterday, works so far. Today the subwoofer is connected, no sound of it (radio and speakers work). I have connected a mass, am at the plus pole of the battery and have plugged two Cinch cables from the subwoofer (red white) to the two connections of the radio (red white). I measured electricity on the plug from the sub, comes on. The subwoofer doesn’t bring a quiet buzz or anything like that even when it’s turned on. I have read several times about Mono cinch or sub cinch, but my radio has two cinch connections as already said. I have an active subwoofer of option. Thank you very much in advance.