The 22 Hz and 33 Hz low-shelf filters are quite similar to a bell filter. The subsonic frequencies
are filtered in such a way that they do not overload the low end of the spectrum (which could be
dangerous for the speakers, or affect dynamic processing carried out after Pulsar Massive in an
undesired way).
Special 22 Hz and 33 Hz low-shelf filter modes with minimum bandwidth.
Pulsar Massive - User Manual - page 11 / 35