The PB-4000 subwoofer thrills action movie fans and audiophiles with staggering output and subterranean deep bass extension down to 13Hz with an amazing degree of subtlety and finesse. A high-excursion 13.5-inch driver and a Sledge amplifier with Analog Devices most advanced audio DSP enables variable port tuning and unlocks a smartphone app with advanced DSP and custom presets for precise and convenient tuning.