Exceptionally tight and powerful bass — a foundation you can build on: Featuring extended response and exceptional clarity, the S-Series subwoofers are more than capable of handling the sonic demands and power output of any Bass Engine® system. This is bass at its best.Cone and Edge: By reinforcing the cone pulp with Kevlar, strength and tear resistance are increased while retaining the beneficial qualities of a pulp cone design. The use of Santoprene®, a precision-molded high quality synthetic rubber, allows thicker sheets to be molded into stable edges with increased strength and higher excursion.Nomex® Spiders: Dual spiders provide extra stability to Alpine's high excursion design, by keeping the coil centred in the gap even when driven to the limit. Additionally, custom oversized progressive spiders were tooled to evenly distribute stress through the long stroke. Constructed of Nomex, the toughest spider material available, tear resistance, strength and durability are outstanding. Dual Custom Progressive.