Amazon.com: 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 Inch
SUNDOWN AUDIO U-15 D4 15" SUB 1500W RMS DUAL 4-OHM SUBWOOFER BASS SPEAKER NEW | eBay
Car Vehicle Subwoofer Audio Speaker - 6.5 Non-Pressed Paper Cone, Black Plastic Basket, Dual Voice Coil 4 Ohm Impedance, 600 Watt Power, Foam Surround for Vehicle Stereo Sound System - Pyle PLPW6D : Electronics
Massive Audio GTX Series 12-Inch 700-Watt-RMS Dual 4-Ohm Subwoofer in the Mobile Audio department at Lowes.com