JL Audio 12W1v3-4 W1v3 Series 12" 4-ohm subwoofer at Crutchfield
Amazon.com: Pyle 10" Car Audio Speaker Subwoofer - 1000 Watt High Power Bass Surround Sound Stereo Subwoofer Speaker System - Non Press Paper Cone, 90 dB, 4 Ohm, 50 oz Magnet, 2
Pioneer TS-1200M 12" - 1400 W Max Power, Single 4Ω Voice Coil, IMPP™ cone, Rubber Surround | Component Subwoofer - Walmart.com