TL;DW: Highpass2 is an unusual-sounding variable-slope highpass filter.
Much like Lowpass2… and yet, not entirely :)
So, the way the interleaved IIR filters act in Highpass is like this: the harder you filter, the more the filter rolls off the very highest frequencies. That’s because it’s like the inverse of Lowpass2. It’s got the same four poles, the same type of tone doctoring (in this case, loose and tight for what bass remains) but the way to use it might be distinct.
I think it works well for getting a subsonic roll-off (perhaps with the four poles of filtering, like a mini ToVinyl highpass) and then using the Loose option to let the bass move a little more. I found it more difficult to distinguish what the funny-named slider was doing, but it’s still intense on high settings. And it’s great for trapping in high percussion because of the clarity of the passband and the way it rolls off over 20K (or higher, if you’re at higher sample rates).
And of course, like Lowpass2, this is here to fix the limitations of the original Highpass on those very same sample rates, going from no filtering to total filtering.
If this becomes indispensable to you, please jump on my Patreon for an additional $50 a year if you’d have paid that for this unusual tool (perpetual license, forever support, all your computers, you get the source code: you know, normal terms and conditions like that). If you can’t afford it, use the plugin anyway, and maybe one day you’ll be better off :) if you just hate Patreon, I’m working on getting some alternate things in place such as Ko-fi. However, in order to set up Ko-fi to be even comparable to what Patreon does, I have to pay them up front. So please help with the Patreon so I can afford to have a fallback position. Probably won’t ever matter, Patreon is thriving and it is only investor logic that has anyone thinking it isn’t :)