SD-3 10 D4 - Sundown Audio 10" 500W RMS Dual 4-Ohm SD Series Subwoofer The SD-3 series truly is a world-class sound quality woofer with low mounting depth, small box requirements, and a reasonable price. Xmax = 14.5mm one-way by 70% BL | RMS Power = 500-watts (300-watts for the 8 model) | Under-Hung low distortion motor topology | Solid pole piece with chamfered edges Black Aluminum 2.5 voice coil former for superior heat dissipation | High Temperature 8-Layer copper voice coil wire | Large aluminum faraday ring (Magnet ID) | Spring Loaded Terminals Stitched-On Tinsel Lead Wires | Optimized for small sealed enclosures | Inverted Rubber Surround to reduce front-mount depth | High strength cast aluminum frames