Sundown Audio SFB Series Amplifier Walk Through 2020 Sundown Audio Sfb-13500d Monoblock 13800w Rms Subwoofers Class D Amplifier New. Dual 0 Gauge Power & Ground Wire Inputs. High Pass Filter 15 to 80Hz (-12dB/8) Variable. Maximum Supply Voltage 16V DC. The item SUNDOWN AUDIO Sfb-13500d MONOBLOCK 13800W RMS SUBWOOFERS CLASS D AMPLIFIER NEW is in sale since Friday, April 4, 2014.