Hooking up a PSW1000...??Question??

confused1234

I want to hook up a PSW1000 sub to my system, but the location I need to put the sub (next to the sofa) is across the room. The question is: what is the longest length I can run a subwoofer cable from the receiver to the sub? With the drops in the walls and the attic run I figured I would have to have a 40' cable. I don't have room next to the Main speakers, space is at a premium on that wall.