CT Sounds How To | Build a Ported Subwoofer Box for 2 12" Subs - YouTube
Focal ISUB BMW 4 Subwoofer - Black for sale online | eBay
KRK S10.4 10" Powered Studio Subwoofer | Guitar Center
Kicker 48CWRT672 CompRT Series shallow-mount 6-3/4" subwoofer with dual 2-ohm voice coils at Crutchfield
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