The Kappa 42.5i features Ceramic Metal Matrix Diaphragm (C.M.M.D.) cones, constructed by sandwiching aluminum between layers of ceramic, producing a lightweight, durable driver. The Plus One C.M.M.D. woofer cone features a low-frequency performance with minimal distortion. Unwanten resonances are eliminated with the use of a cast-polymer basket and hi-roll rubber surround. High notes are beautifully reproduced by a C.M.M.D. balanced dome tweeter.