The new SPL subwoofers feature the latest generation of Velodyne's patented "ERS" (Energy Recovery System) Class-D digital amplifiers. The ERS amplifiers are over 95% efficient. This gives us incredible power from a very small package. The unbelievable efficiency contributes to cool operating temperatures, reliability and long term operation.To compliment these powerful amplifiers, Velodyne has developed massive drivers with multi-layer, Kevlar-reinforced, resin cones mounted in die cast aluminum baskets. Each driver incorporates a unique, inside/outside two-layer copper voice coil that assures linear travel, and allows the heat dissipation needed to handle the gigantic power delivered by the "ERS" amps. These technological breakthroughs in amplifier and speaker design allow the SPL subs to create room-shaking bass for Home Theater applications in spite of their tiny sizes. Minimize