MS-10SD4 Slim - JBL 10" Dual 500W RMS 1000W Max 4-Ohm Slim Series Subwoofer
JBL Club WS1000 10" Shallow Mount subwoofer w/SSI (Selectable Smart Impedance) Switch from 2 to 4 ohm Bundled with Alphasonik Earbuds : Electronics - Amazon.com
JBL 102AM Stage Series 10" 4-ohm component subwoofer at Crutchfield