SubFilter is a freeware subsonic filter plug-in with a selectable cutoff slope of -12, -24 or -36dB/Octave.
The filter is extremely useful for removing thumps, bumps and low frequency rumble noise from your audio.
SubFilter has 2 controls: cutoff slope and crossover frequency. The cutoff frequency is variable from 10Hz to 200Hz. The passband is flat (Butterworth filter) and has unity gain.
Visit Jeff Rippe’s website for more information and a link to download SubFilter VST.