I have an Essence bass and acouplr of question about Alembic pickups. What is the MXY configuration?
 
- single or stacked single ciol?
 
- dual or humcanx, ect,
 
- wired in series or parallel
 
- etc.

Except for Series I/II pickups we make stacked humcancelling pickups. There is a coil near the strings with a magnetic core and a humcancelling non-magnetic core coil directly below.  
 
Unlike other's pickups, we don't use them as tone controls - they just report the strings' activity to the electronics where the tone control happens.