The HDL 118 is a high output active subwoofer system for high SPL sound reinforcement applications. The HDL 118 is designed to be either ground stacked or flown with the HDL 3112 Line Array System. The HDL 118 was designed with a 1000-watt 18-inch woofer. The HDL 118 incorporates a High Current D-CAT power amplifier system capable of producing upwards of 1000 watts RMS as a stand-alone system. The HDL 118 can deliver over 1000 watts RMS power. The amplifier receives its input signal from an internal 4th order crossover network specifically designed to provide optimized phase and frequency response for a composite system. The internal amplifier is based on ISP Technologies patent pending D-CAT (Dynamic Current Amplifier Technology) amplifier technology. The D-CAT technology is capable of delivering extremely high output current providing an improvement in transient response, output current, and a noticeable improvement in PUNCH. The D-CAT amplifier technology utilizes a monolithic power amplifier driver that reduces parts count and greatly improves reliability. The D-CAT amplifiers provide improved reliability by including short circuit and over temperature protection.