I wired a surround sound system with inwall speakers all around. I used regular 18 guage speaker wire. I also ran this wire for the sub through the wall to the back of the room (about 40 feet) I connected RCA jacks to each end of the wire but the sub doesn't work through this connection.

I know the wire is in good shape so I think I'm using the wrong connectors or maybe I just attached the connectors to the wire incorrectly.

Any help would be appreciated.