Alpine SWR-1522D Type-R 15" subwoofer with dual 2-ohm voice coils at Crutchfield
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
Alpine W10S4 | 750W Max 10" Subwoofer with Ported Enclosure
2) Alpine SWS-15D2 15" 3000 Watt Car Subwoofers + Vented Sub Enclosure Box | Audio Savings