Pioneer TS-W311D4 Subwoofer in an L-Ported Box Bass Test - YouTube
Pioneer TS-W311D4 Champion Series 12" subwoofer with dual 4-ohm voice coils at Crutchfield
Pioneer 12 Inch 1400 Watt Subwoofer Car Audio Power 4-Ohm DVC Sub | Car Speakers - Newegg.com
Amazon.com: Pioneer TSW312D4 Champion Series 12" 1500 Watt Dual 4 Ohm Voice Coil DVC Car Subwoofer : Electronics
Alphasonik AS12DF 12" 1500 Watts 4-Ohm Down Fire Shallow Mount Flat Enclosed Sub woofer for Tight Spaces in Cars and Trucks, Slim Thin Loaded Subwoofer Air Tight Sealed Bass Enclosure - Walmart.com
TS-W311D4 - Pioneer 12" 1400W Dual 4-Ohm Champion Series Subwoofer