Lowrider tone roll off part

[Spacebass]

Hallo, i was looking at the simulation of rolled neck pick up, and I m thinking about lowering it a little,but I dont get the filtering part, in the lowrider 2015 pdf, that i ll refer to, R42 (22k) and c18(10n) form a lpf at 720hz, right? But what abot r43/c19 and r44/c20? If using a passive bass (pb or jb), would it benefit from having the low pass filter over 400hz? And what about adding a little hpf before? A 22n with a 120k to ground or something like this? Thank you