JBL S2-1024SS Series II 10 Inch Subwoofer with SSi Selectable Impedance - 2 or 4 Ohm - Creative Audio
Amazon.com: JBL Club WS1000 10" Shallow Mount subwoofer w/SSI (Selectable Smart Impedance) Switch from 2 to 4 ohm Bundled with Alphasonik Earbuds : Electronics