It combines a 1-Ohm stable circuit, installation flexibility and a superior high-power output of 1600W Max.FeaturesBig Power, Small Size Pioneer’s new extra-efficient Class-FD digital amplifiers mark a dramatic improvement in power output capability, yet are 50% smaller than the current GM-Series Class-AB amplifiers. That makes them more versatile in terms of installation as well as performance. Improved Circuit Design To prevent circuit shutdown, Pioneer’s new digital amplifier circuit “Protection Control System” senses its internal temperature and automatically moderates input level accordingly. Stable, durable circuitry lessens the risk of high input power for the unit to achieve a 1 Ohm connection. This design enhances the flexibility to connect multiple subwoofers to a system. Variable Low Pass Filter For extra flexibility, variable LPF and HPF make audio frequency more adjustable according to subwoofer characteristics and personal listening preferences. The GM-D9704 LPF and HPF are adjustable from 40 Hz to 500 Hz.