the L7 is a high performance sub-woofer made by Kicker car audio. it is in the shape of a square. it is the big brother of the L5 which is also a square shaped sub-woofer made by kicker.
example 1)
Gords: did you see Game's car system i heard he's pushing two L7s
Cheese: I know i was there when he set it up, its loud as hell!