Speaker has an operating frequency bandwidth of 55 Hz to 20 kHz. This response can be lowered to 32 Hz 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 are defined by the drive parameters contained in the amplified controllers.