Help with bipolar envelopes

devolution

I am having some trouble understanding what the envelope does to parameters besides level. The manual describes them as bipolar, which is a bit different than how I generally understand envelopes, which tend to be unipolar (in my experience) from whatever the base level of the parameter is.

What I'm seeing is that you set the base level of the parameter, and then the modulation strength effectively creates a bound around that point, both higher and lower, with the range dictated by the strength. So, for example, if I have LPF set to 20, and then Env2 patched to modulate the frequency with strength 10, the filter range would be 10 - 30 (not sure if it adds up like that). Then the envelope shape would occur over that range of 10 to 30. And then sustain sets where it sets, with 25 being the base range that I set (20 in this example). Is that all right? And then, no matter what, when you release the trigger it drops down to the low level (10, here).

Maybe this is super obvious, but I'm struggling to get the sounds I'm envisioning. I want to make a wub sound, where the filter opens up and closes to a point where it can then ring out. But basically the filter starts way lower than I want. Any tips for how I can get my head around this?