Most Impact on Sound Stage/Imaging?

Small cabinet, narrow baffle, rounded front edges.
Coincident drivers.
Active crossover.

Addendum to my last post...proper speaker placement as well.

Room treatment.

C.. if you seal the inside of a wooden cabinet with Cascade V-Bloc that is a water based product designed to be absorbed into the wood pores and drys like concrete. Also use non ferrous fasteners for all drivers and crossovers,replace all resistors with non inductive type as sold by North Creek and others. Direct couple the speakers to the floor with points that are designed to collect, focus,and discharge resonant energy to a larger mass or ground.Tom

Fix the room, amazing results.. I just did it and its like adding a whole new system. The room is a system in itself period.

That's easy, Room Treatment! Until you've heard what a properly treated room sounds like you're missing a huge part of high end audio.

Well, room treatment is not possible (standard reason: negative WAF). I simply wanted to know which of the three (drivers, cabinet, crossover) affected soundstage/imaging the most.

Steve O.

Well Crossovers done right will have the most influence on actual sound, but the cabinet will be semi important for better more solid clean transients, especially at higher volume... Drivers if they are good can be way better if on very good crossovers.

If you email me then I can briefly describe how using the virtual room treatments from Machina Dynamica may be just what you need. Great WAF because can be hidden in plain sight, or barely noticeable when in position.
I have listened to before-and-after results of true speaker builder-modifiers, and the results working outside the cabinets with Machina Dynamica can be as effective, sometimes even better, than what is heard after a great deal of hard work by the builder-modifiers.
Certainly recommendable for those listeners who are all thumbs.
Additionally, inexpensive Big Fat Black Dots (speaker footers) from Herbiesaudiolab.com enable many speakers to sound their best.
Finally, after years of DIY speaker building, at least one experienced speaker builder I have encountered feels "the magic is in the cross-over".

Machina Dynamica? Please disregard - no further mention.

Crossover and rewire the box with solid enamel coated wire, no teflon coated wire. Also as others said- treat the room.

ET