Hertz DS 25.3 Dieci Series 10" 4-ohm component subwoofer at Crutchfield
B&C 18DS115-4 18" Professional Neodymium Subwoofer 4 Ohm
Subwoofer Specific, Sundown – Atrend USA
Audison APBX 8DS Prima Series 8" 4Ω DVC Sealed Subwoofer Enclosure System - Creative Audio
Amazon.com: DS18 SLC12S Car Subwoofer Audio Speaker - 12" in. Paper Glass Fiber Cone, Black Steel Basket, Single Voice Coil 4 Ohm Impedance, 500W MAX Power and Foam Surround for Vehicle Stereo
DS18 EXL-XX15.2DHE High Excursion 15" Subwoofer 4000 Watts Max 2-Ohms DVC audio subwoofers
DS18 EXL-XX15.2DHE High Excursion 15" Subwoofer 4000 Watts Max 2-Ohms DVC audio subwoofers