Powerbass M-1004D 10-Inch Dual 4 Ohm Subwoofer 650W Max Proprietary 4-layer, Non-pressed Paper, DDC Finish Cone Dynamic Damping Coating (DDC) for deeper, distortion free bass Large Roll Santoprene Surround allows maximum excursion and precision bass reproduction Improved Dustcap reduces resonance and non-linear movement with cone Massive Motor Structure for high power handling and maximum output Dual and Single 4-ohm Voice Coils made with pure PIW wire looped through the spider