I have a Sony 5.1 speaker set with a passive subwoofer that I would like to connect to a Sony STRDN1080 AV receiver. I have all the speakers connected and get sound through those but there is no connection for the wires of the subwoofer, only 2 female RCA connections, one of which is to be used according to the receiver instructions. To achieve this, I bought a speaker wire to male RCA connector but the subwoofer does not appear to work. When I run Easy Speaker Set Up on the receiver all the speakers produce sound, but only a very faint sound is coming out of the subwoofer and as a consequence the set up fails. I may be wrong but I think this is because it is a passive subwoofer and the connection I'm using is intended for an active subwoofer with its own amplifier. As I don't really want to buy a different subwoofer, what are my options? I have heard you can buy an external amplifier but I have no idea how to connect this? Could someone please help me, bearing in mind I know little about audio equipment? Is the idea to buy an amplifier with its own power supply, connect the wires of the passive speaker to this and then connect the amplifier with a male to male RCA cable? What amplifier and cable would be recommended?