Amp gains, subsonic filter, boost & LPCF | DIYMobileAudio.com Car Stereo Forum
Harrison Labs Subsonic Filter FMOD 37Hz High Pass @18dB Electronic Crossover | eBay
One Channel Car Audio Mono Amplifier, 3900 Watt Max @ 1 Ohm High-Powered Mono Car Amplifier with Subsonic Filter and Low Pass Filter, Cooling Fans, White
Subsonic High Quality Stereo 24db 4th order 15/20/25 Hz Active Filter MSS-3 | eBay
Mtx Thunder1000.1 Class D 1000 Watt Rms Mono Block Compact Vehicle Stereo Sound System Amplifier W/ Selectable Bass Boost, & Variable Subsonic Filter : Target
DB Systems-DB Systems Subsonic Filter-Turntable Accessories|Acoustic Sounds