Alpine R-Series RS-W12D4 12" Shallow Mount Subwoofer with Dual 4-Ohm Voice Coils
Alpine R2-SB12V Single Type R2 12-in Subwoofer in Vented Enclosure - Creative Audio
Amazon.com: Alpine R-W12D4 Car Audio Type R Series Sub Dual 4 Ohm 2250W Peak 12" Subwoofer and HA-SWKD Dual Subwoofer Sub Box Install Kit : Electronics
Alpine SWR-1222D Type-R 12" subwoofer with dual 2-ohm voice coils at Crutchfield
LAB SlapBox™ 2.25 ft^3 Ported MDF Enclosure Box for Single Alpine 12" R-Series Subwoofer