The Kappa Series subwoofers feature SSIâ"¢ (Selectable Smart Impedance), a HARMAN-exclusive impedance selector, that lets you choose a 2- or 4-ohm impedance at the flip of a switch. Our proprietary aero-cooling design keeps the voice coil cool while optimizing power handling and longterm reliability. And, the acoustically damped glass-fiber cones have been engineered to minimize distortion and unwanted artifacts. More performance. More flexibility. You get both when you step up to a Kappa subwoofer.