Rockville RVW1800P4 1800w Raw DJ Subwoofer 4 Ohm Sub Woofer 107OZ Magnet, 18" Rockville RVW1800W4 1800 Watt 18 Raw DJ 4 Ohm Subwoofer. Kevlar Reinforced Ultra Stiff Paper Composite Cone. Pulp Composite Dust Cap. Expanded and Rolled Steel Basket. Treated Accordion, Asymmetrical W Cloth Surround. Ultra Saturated, High BL Magnetic Motor Gap. 3 High Temperature 4-Layer CCAW High SPL Voice Coil. Linear Progressive Conex Dual Spider System. Nickel Plated Banana Plug Terminals The Rockville Bass Rider woofers voice coil use a specially formulated, polyimide-insulated, high temperature wire, designed especially for high SPL response. The winding is bonded onto an incredibly durable and heat resistant aluminum composite former. The voice coil winding length is an incredible 1, which is 80% longer than most standard pro woofers voice coils. The long coil dissipates heat over a larger area and the increased length drives the cone to higher excursions. The voice coil assembly is bonded to the cones double, linear-progressive Nomex spider, using a thermoset epoxy adhesive. The spider and surround are bonded to the frame with a high strength cyanoacrylate adhesive, which is also used to bond the dust cap to the cone. The magnet motor structure is all new, and designed with a back plate and pole piece which are forged from a single massive block of low carbon steel. Utilizing an extended pole piece beyond the front plate improves magnetic linearity and voice coil cooling. The yoke and washer plates are 10 mm thick for extreme X-max and peak-to-peak excursions. With a narrow gap design and a high Y factor strontium magnet, Rockville Bass Rider subwoofers provide 75% more magnetic energy in the voice coil gap than typical pro audio woofers.