i think you are right, but i tried for the last two days to get a algo with just  a low pass filter at 100 Hz without any other sound modulation. I cannot remember which H9 Max algo i used back then (when i had the H9 Max), but it really was easy, so much i remember, to get a LowPass sound. but as far as i know i tried all the H9 Max algos available in the H90 so far.