Presonus AIR XD SUB 15 Active Extended Definition Subwoofer - 15"The PreSonus AIR XD Sub 15 is a high performance active subwoofer designed for professional use, delivering deep, extended low end and high SPL for any application. Its custom 15 inch low frequency driver with enlarged 3 voice coil provides efficient power handling and tight, dynamic bass with minimal distortion, while advanced tuning optionsincluding variable lowpass filtering, alignment delay, and cardioid end fire array presetsallow precise control