Rob, Your sub is equiped to connect to recievers that don't have subwoofer pre-outs. If you have a DD reciever don't worry about it but someone that has an older surround reciever or a stereo reciver/amp may want to connect to a subwoofer and have to use the speaker level inputs direct from the L/R amp outs, through the sub to the speakers. In this scenario the sub gets the signal it needs to amplify and the speakers get their still are powered by the reciever/amp and no additional outputs from the reciever/amp are needed.