Electro Voice Speakers EV DL15STSpeakers are high-efficiency designs highly refined from years of development and field experience. They employ extended-length voice coils for high-impact reproduction of dynamic low-frequency program. All Electro Voice Speakers EV Speakers feature proprietary heat-transfer systems for unmatched power capacity and reliability. Kevlar-fiber composite cones are used to provide structural strength to resist collapse during explosive dynamic peaks and to provide internal mechanical dampening to minimize resonance’s that can change the character of the sound at high levels. DL and EVX woofers are made of cast aluminum frames with push terminals and all features Ring-Mode Decoupling (RMD) except for the DL18MT and the EVX180B.