OK i just bought an L5, 15 inch kicker sub, and a 1.5 cubic foot sealed box. My question is do i really need to use polyfill? i mean i know alot of people that use it for smaller boxes, but my box meets the minimum specs for cubic feet, so i dont see why i need it. yet everyone ive talked to says i have to use it. anyone have any useful info for me? any help is appreciated. thanx!