Ultra Shock Subwoofers are engineered for performance and sound quality. New materials used for surround and spider, revised stronger baskets, and improved stronger/larger motor structures. Suspension: The surround is now a rugged Santoprene rubber surround that will support long linear excursions with improved reliability. The high flex life Conex spider/damper has been revised in roll shape and material to compliment the improved surround. Motor Structure: Magnet sizes and voice coil winding lengths have all been adjusted for improved performance output and sound quality. The motor structures were engineered using FEA analysis to provide low distortion output at both high and low power levels, which results in more linear motor force within the subwoofers normal operating excursion and power levels for both negative and positive current through the voice coil.