Recoil SW10P Car Audio 10 Inch Active Subwoofer with Passive Radiator, Built-in 600W Amplifier, Include Remote Subwoofer Control and 8AWG Complete Wiring Kits - Walmart.com
Passive Eminence 8" and Dual Passive Radiator Subwoofer Kit
Amazon.com: Earthquake Sound SLAPS-M12 12-inch Passive Radiator for Home and Mobile Audio Subwoofer Enclosures : Everything Else
Dayton Audio RSS460-PR 18" Reference Series Aluminum Cone Passive Radiator