The Alembic Activators are different than regular active pickups. "Normal" active pups just boost bass and treble frequencies (and sometimes mids) - Activators are filters with sweepable frequency. It's a subtle difference - not too good at explaining it
An analogy might be to compare it to EQ - fixed band (graphic) versus parametric. Most other tone controls in basses leverage "low pass filters" like the Alembic, but rather than just control how much of the high end is rolled off at a single fixed frequency point, the Alembic setup lets you sweep this filter cutoff point - kinda like a parametric EQ would on a given band. I don't know too much about what's available out there in this space for active bass setups - I'd imagine that there are other active setups that do this too, but that's one of the things that always made the Activators seem a little different to me.
I prefer just having a good passive setup in a bass and use outboard gear for processing, but the Alembic setups can in fact sound really nice to me. I'm not much for over-the-top higs, and I like that I can get a great "passive bass sound" out of my Distillate!!!
I think I get along with their setup since its not about boosting crazy amounts of highs and scooping mids, and also (at least in their basses) I like the "Q" (aka filter resonance) control that kinda puts a little peak at a nice spot in the mids to punch thru the mix sometimes. You can really dial that in on the Series basses, but even with the more limited settings on the distillate its been useful to me. I don't think the Activators have that feature.
That setup on CL is a nice deal for a set! I'd never buy a new Activator setup, though, since you can score a used Spoiler or Distillate for not too much more than that depending on the time of year (prices always seem very cyclical to me on the Alembic stuff)
