ETX-18SP from Electro-Voice is a powered subwoofer, it can be used in a variety of portable and permanent applications. The DSP (Digital Signal Processing) menus offer extensive configurations, crossovers, true cardioid presets, protection limiters, EQ mode, and a lock out mode that prevents casual changes to the system. Loudspeaker system performance is optimized via an LCD screen. The front LED indicates power or can be configured to indicate limit. EV's FIR-Drive technology utilized the latest FIR(Finite Impulse Response) filter technology to optimize transducer linearity and advanced limiter algorithms for independent peak and thermal transducer protection. True cardioid DSP preset delivers true cardioid response across all frequencies. The enclosure is constructed out of 18-mm plywood finished with EVCoat. Subwoofers include professionalgrade castors, and combination pole mount receptacle for threaded and unthreaded loudspeaker poles. ETX Powered Loudspeakers combine EV-engineered intelligent DSP, high-powered amplifiers and high-efficiency transducers to deliver that legendary EV sound and performance.