Even tho subsonic is an "effect"...it really isn't....an effect.....it's just a sound...I think it's a simple sine wave..... (subsonic effect = sub bass sound). You don't even need sound to use it, like you could apply subsonic to a silent sample & it would sound the exact same as if you applied it to a sound (I do this a lot to make bass lines).
The knobs on the sx adjust -
how much the "subsonic sound" plays with the original sample (wet/dry mix),
what key the "subsonic sound" plays in
& how much the "subsonic sound" plays (can make it only hit at certain times or be a full on drone, but can't pick where it hits.... when barely on it hits at the loudest peaks, turn the knob up & the hits get longer & longer).
Again, I'm pretty sure it's a sine wave. Find a sine wave & you have subsonic effect
Bug reports & end-user tech support for Akai's generation of MPC Software 'controllers' - MPC Touch, MPC Renaissance & MPC Studio.