Pioneer TS-D12D4 D-Series 12" subwoofer with dual 4-ohm voice coils at Crutchfield
TS-W3003D4 - 12" Champion Series PRO Subwoofer with Dual 4 Ω Voice Coils and 2,000 Watts Max Power (600 Watts Nominal) | Pioneer Electronics USA
Amazon.com: Rockville W12K6D4 V2 12" 2400w Peak Car Audio Subwoofer Dual 4-Ohm Sub 600w RMS CEA Rated : Electronics
Amazon.com: Alphasonik AS8DF 8 inch 600 Watts 4-Ohm Down Fire Shallow Mount Flat Enclosed Sub woofer Slim Thin Loaded Subwoofer Air Tight Sealed Bass Enclosure : Electronics
Pioneer TS-6900PRO Speaker 100W RMS 6 x 9 Pro 2-Way Coaxial Car Stereo – Sweetheart Deals