Disclaimer? I'm not Mathew Weiss, thus, I can't spot out if a small-Q-ed boost of 0.3dB located only in the side of a mix is throwing the whole track off-balance.
That being said, when testing out Mellowmuse's EQ1A, while largely unimpressed, the High Pass sounded especially funky... and not good funky. I thought I might be spoiled by BAX and Butterworth curves, but took it into PluginDoctor to see what the score was.
Anyone have any ideas on what in the hell this HP "curve" is supposed to accomplish, exactly?

 

This only happens at ~ 5Hz with a Q higher than 2.2. If you raise the freq or lower the Q, it's gone.
Could be even a display failure of PD.
EDIT: Yep, if you set the quality to 'highest' it occurs only above Q2.6.

 

I appreciate the response.
Seems kind of odd, too me, with EQ curves at any Hz, but again, I'm no expert, so there's probably a reason for this. Haha, I *do know odd, though, as I've been trying to acclimate myself to Black Rooster's KH-EQ1--that thing has some crazy, per-band, tightened pultec-ish curves when the cut/boost starts getting pushed.

 

This also happens with EQuilibrium and others even if they don't reach down to 5Hz.

I need to get the demo. What do you think of its sound?

 

It's Black Rooster, so it's solid, but it seems like an EQ that is suited for specific tasks, as opposed to a go-to. I tried it out and just went by my ears, and after trying it out on some Kontakt instrument--a PCS Mark I, OTS Flatwound Bass, among others, and various drums and breaks--I checked out the curves. I thought it had some strong, interconnected bands, but seeing the curves helped me understand what it's actually doing. The bands are set up so that the farther you boost or cut, the more the more a small area directly to either side of the frequency is inversely affected, which can be a help or hinderance, depending on what you're going for.
The saturation is solid, but it behaves very differently with different audio sources. The stepless Mid/Side/Stereo is a nice touch.
Honestly, it's a plugin that you have to tool around with for a while to see how you're going to use, if at all, but it is quality. One thing that impressed me was, despite its tighter Qs when you start really cutting and boosting, even with the surround, inverse boosts or cuts, it has that quality in which it doesn't sound like it's doing too much, but when you bypass it you're like "Ooooooh, okay. It's fully working." It's very musically smooth transition, kinda like TDR's SlickEQ, but with out the gentle slopes.
Basically, this plugin is the reason companies put up demos. I like it, I'm just still getting a feel for it.

 

Ah, kind of a resonant bell. Pretty rare but not completely unknown.

Sounds like an EQ worth trying out.