Alpine SWR-1242D Type-R 12" subwoofer with dual 4-ohm voice coils at Crutchfield
BOSS Audio Systems CXX104DVC Chaos Extreme Series 10 Inch Car Audio Subwoofer - 1000 Watts Max, Dual 4 Ohm Voice Coil, Sold Individually, For Truck Boxes and Enclosures, Hook Up To Amplifier
Alpine SWX-1243D Type-X 12" subwoofer with dual 4-ohm voice coils at Crutchfield