Speaker has an operating frequency bandwidth of 55Hz to 20kHz. This response can be lowered to 32Hz with the addition of the SB18 subwoofer. It contains a 3-inch diaphragm compression driver coaxially loaded by a 12-inch low frequency transducer mounted in a bass-reflex tuned enclosure. In passive configuration, the 12XT onboard crossover network uses proprietary third order filters. The linearization and protection of the transducers is defined by the drive parameters contained in the amplified controllers.