Orion CO104S Cobalt Series 10" 4-ohm subwoofer at Crutchfield
Amazon.com: Orion XTR Subwoofer DVC 4 OHM Max Music Power Watts Subwoofer Black Speaker Car Stereo Bass Woofers (XTR104D, 10 Inch - DVC 4 OHM) : Electronics
Orion HCCA Competition Subwoofers - YouTube
LAB SlapBox™ 1.50 ft^3 Ported MDF Enclosure Box for Single Orion HCCA 10 Subwoofer