I'm looking at getting the specialized alembic pickups for my musicman stingray 4.  Its not on Alembic's website yet but it was recommended to me when I asked support about pickup installation.  For the most part I'm unsatisfied with my musicman, it has some good tones, but not a lot of versatility which i need since I play jazz, funk, and r&b.  I'm hoping that the alembic pickup will change things (since there's no way in heck i can afford a whole alembic).  Has anyone bought and used these pickups for their musicman, and what did it do for your sound?

Surprised that a musicman cannot get the sounds you want especially for funk & R'n'B. Mark King used one on one of his albums, then there is Louis Johnson, the late Bernard Edwards and many more.
I put a pair of Alembic Activator P/J pu's with twin vols, bass & treble on a 1983 japanese Squier(now donated to my son) and it transformed the sound completely!
Gone was the  passive dull thud and lack lustre top, loads of bass and hi fi treble with all the stuff in between.
I own a Mark King standard with the humbucker pu's and filters with 2 position Q switches, the higher alembics have variable Q controls, single coil pu's(plus dummy humcanceller) and they give a totally different sound although it took me the best part of six months to get to grips with the filters.
There are some great threads in this section explaining how they work although they are complicated in the theory but using ones ears(as we all do) should get you there.
The main difference with bass, middle & treble on your m/man and the filters is subtlety, only slight adjusting of the controls produces huge tonal variations.
I guess the guys at Alembic didn't bother producing a replacement pu for the musicman as they must have thought that it was good enough already!!
Anyway hope you fine what you are looking for

Terry, there was a recent posting from Mica announcing that they now offer Activators specifically for installation in a MusicMan bass.

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My musicman Fretless was actually the guinnea pig for this pickup I think.

I have a 78 Musicman Sabre fretless and I really like the sound I get from it. But I have never played an Ernie Ball.

MM's are one of the few basses I wouldn't think of for trading out a poor-sounding factory pickup.  That being said, a MM with FatBoys would be a knockout.  Of course, a 2x4 with FatBoys would be a knockout!
 
So ALEMBIC is offering MM shape Activators now?
 
J o e y

Mica stated earlier that it might be released by the end of this year; do a search if you wish.  Of course, it would include the preamp section as well and not just a pickup. I believe she said it might have some sort of mid control.  I think interested parties should stay tuned in.

Don't get me wrong, the MM pickups are very good at producing the sounds they're designed to.  I certainly can get some cool tones with it (especially with my rig: bag end 2x10 and a mesa/boogie m-pulse 600) but I'm mostly concerned about dynamics (I guess I wan't being really clear).  The MM pickups don't seem to be able to pick up dynamics as well as others (e.g. EMG in spector, MEC in Warwick, Alembic).  Instead it tends to produce that dull thump.  I don't necessarily want to loose that, I would just like that to be an option in addition to having nice dynamics.  Would alembic MM pickups provide this variation?

Also, for those interested, what Alembic offers is the retrofit MM pickup with vol, high, pan, and low.  I'm told that later this year they'll be offering one with a mid instead of the pan which is more typical of the MM electronics.  They're waiting for the midrange control before they offer it on their website.

Does any one have a theory over the 'dull thump' that juggernaught refers to?? Could it be the exposed pole pieces pulling on the strings, Am I right that it is a high impedance pu feeding into a low impedance pre amp with resistance conversion. My electronic knowledge limited as it is would explain this??

Maybe the treble control is broken? You should be able to get some ear-splitting treble out of any (active) MM.
 
If it's an old StingRay, perhaps it has the foam mutes in front of the bridge saddles all the way up?

No, its not an old Stingray and the treble (as far as I can tell) is not broken.  
(Forgive my lack of language in accurately describing the sounds coming out of my bass.)
The treble can be very present but it sounds very dry to my ears (and pooly shielded. oh, the buzz!).  The lows and mids are quite nice though.  The dull thud that I'm referring to may have something to do with the quality of the treble, but I'm not sure.  I'm basically trying to say that I hear insufficient response when I try to put dynamics in.  (Maybe I just don't know what I'm talking about )  
However, I tried out an Alembic at a used store and felt that I heard I much higher *quality* of tone overall (including dynamics) which was very appealing to my ears.  This influenced me into looking into pickups for my MM.  But I'm uneasy about making a commitment b/c of $$$.
Thanks for your comments so far.

Something else to consider is the wood and construction of the bass itself. These too will heavily influence the tone and overall sound of the bass.

The dull thud is probably the signature accent on the low-mids. Not sure how much of that is in the electronics - pickup placement is probably a big factor in that as well.