for my tastes (with active bass) the Aguilar Filter Twin has beat them all. I currently have the Source Audio C4, which does all the Spectrum Filter stuff as well but I still use the Filter Twin for envelope sounds. The blending of the up and down sweeps is a key feature and it just hits the sweet spot to my ears. I'm also currently in possession of the TWA MiniMorph which sounds wild and great but the C4 can cop that one pretty well and it might be going soon.
Others I've owned:
Dr. Scientist Dusk (liked the other modes better than the Envelope mode)
SolidgoldFX Funk Lite (uninspiring)
EMMA Discumbobulator V2 (quite good and has a separate boost switch)
Keeley Neutrino V2 (worst filter of them all)
Keeley Bubbletron (didn't get it for the filter, the Sample and Hold is great)
Mr. Black FwonkBeta (gets lots of love but didn't mesh with me)
Source Audio Soundblox 2 Manta (lots of options, sounded good)
Lovepedal Rubber Chicken (4 knob version; liked this one too just wasn't quite there)
MXR M82 Bass Envelope Filter (uninspiring)
Just my opinions, good luck on the search!
Similar to
@jgtwentysix , I've used the MXR, Mr Black Fwonkbeta, Emma V2, and the Aguilar Filter Twin.
- The MXR didn't work for me because it's bandpass, and regardless of all its knobs, it can only give you variations on one sound. Off it went.
- Really dug the Emma V2 but a few things didn't work for me: it wasn't rude enough and its downsweep was really noisy. Was okay in a mix as long as you played, but any rest or pause would being out that hiss. The secondary boost option was great, but not enough to keep it. Off it went.
- I currently have both the Mr Black and the Aguilar.
The Fwonk is nasty as all hell. Requires a compressor immediately afterwards or it'll blow your speakers/ears/amp. It's important to keep the highs dialed in with the juice knob almost entirely CW. Sounds amazing stacked with other pedals. A great filter imo.
I was surprised by the Filter Twin. It didn't seem rude enough on the first go around, but it did something others struggled with in my experience. It sat perfectly in the mix. Not below and indistinguishable except for small bursts, not on top where it would interfere with higher harmonic content. It sat there just perfectly. The up and down sweep mix is surprisingly useful, so you can go fully up or fully down or mix them both. And the threshold was simple to trigger across the sweep. Still have it, still dig it.
Filters are the most personal of effects. The triple As surely come into play here: your axe, attack, and articulation. A fantastic filter for me may sound awful with your set up and/or style. I haven't found the perfect filter, even though I had a Microtron IV and had to return it because it didn't trigger, so that may still be out there for me. For now, the Fwonkbeta and the Filter Twin are the winners. Hope this helps.