JBL ES150PBK 300-Watt Powered 10-Inch Subwoofer - Black A JBL computer-optimized bass-reflex port provides deeper bass and less turbulence. Use of premium components gives you less distortion. These speakers are designed to look good anywhere with a style that equals their substance. The JBL ES Series uses cellulose-fiber cones reinforced with a ploymer coating for uniform pistonic motion. This eliminates internal resonances, without increasing cone mass.For any further queries please contact JBL Customer Support Number@1800-422-8027.