John, I thought the Highpass can only be engaged through the high level(speaker terminals) connection??

Wid, I believe John is refering to hooking up RCA from the source(ex: cd player) directly to the sub, then route another pair of RCA from the SUB preout to the 3480's main-in where jumpers connected. Now, instead of using the main-in shouldn't I use CD-IN or any other line level input instead??