LowEnder is a sub-harmonic synthesizer that uses the venerable dbx 120 series sub-harmonic synthesizer as a starting point, but adds some unique additional features for the user.  As can be seen in the interface, on the left side, the input section allows for mixing dry to wet signals, and allows for the master output to be adjusted.  Its processing section has two bands to allow for harmonic additions - very much like the dbx unit - and three range settings for different processor responses, which allows for tuning of how the processor treats its input.

It also has a low-frequency-tuned gate, which allows further tuning for transient effects.  The bass output settings govern the drive of the sub-harmonic synth, and the low-pass filter allows the output signal to be further filtered to taste.  LowEnder makes crushing sub-woofer effects with terrific ease, it is easy to use and it costs a very reasonable $69.  A top pick in every way. RTAS, Audio Units and VST formats.