JBL S3-1024 Series III 10" component subwoofer with impedance switching at Crutchfield
Amazon.com: JBL Club WS1000 - 10” shallow mount subwoofer w/SSI™ (Selectable Smart Impedance) switch from 2 to 4 ohm, Black : Electronics
1 Pair (QTY 2) of JBL STADIUM122SSI 12” High Performance 1350 Watts Peak Power Car Audio Subwoofers with SSI (Selectable Smart Impedance) - Road Entertainment