Wet Sounds Revo 12 PSE (Black w/black grille) Revo Series sealed marine subwoofer enclosure with 12" 4-ohm subwoofer and 12" passive speaker at Crutchfield
Electro-Voice ZX-1 Sub - 12" Passive Subwoofer F.01U.267.692 B&H
Amazon.com: Earthquake Sound SLAPS-M12 12-inch Passive Radiator for Home and Mobile Audio Subwoofer Enclosures : Everything Else