Alpine SWR-1242D Type-R 12" subwoofer with dual 4-ohm voice coils at Crutchfield
Alpine 12" Subwoofer S-series w / Dual 4-Ohm Voice Coils
Alpine R-Series RS-W12D4 12" Shallow Mount Subwoofer with Dual 4-Ohm Voice Coils
Amazon.com: Universal Car Stereo Vented Port Single 12" Alpine S-W12D4 Type S Car Audio Subwoofer Custom Sub Box Enclosure Package New Without Amp : Electronics