Customer Reviews: Alpine SWR-12D4 Type-R 12" subwoofer with dual 4-ohm voice coils at Crutchfield
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-1242D Type-R 12" subwoofer with dual 4-ohm voice coils at Crutchfield
Alpine SWR-1221D 12" Dual 2-ohm Voice Coil Subwoofer at Crutchfield