JBL  MRX528S Compact  Double 18-Inch 800-Watt Continuous Premium Subwoofer Two JBL Special 18 inch 2044H Woofers for Extended LF Output Large Vents for Reduced Distortion Tough "Duraflex" coated paint enclosure finish and Heavy Duty 16 gauge Perforated Grille Tough Void Free Plywood Construction Internally Braced for Maximum LF Performance Upright Format Sub for easy stacking of MRX Top Cabinets without the need for a pole.