The MK Is can be divided into two groups, pre ABL and ABL.  Basically, the ABL function boosts bass at low volumes and rolls bass off at higher volumes to prevent distortion/ driver damage.  If you're going to push the speakers to higher volume levels, the ABL type are a better choice. ABL was introduced around S/N 10145230.

The late MKI and MKII are electronically the same and use the same drivers. The main difference is the physical construction... different cabinet and heatsink / inner cone assembly. I imagine these changes were done for production reasons, but I don't definitely know. Might be some slight differences in the cabinet resonances due to the difference in physical construction.

EDIT: I'm seeing that people are using MKI/II to refer to pre/post ABL.   I always considered all 8000s below S/N 17255079 to be MKIs and the change to MKIIs accompanied the physical changes to the heatsink/cabinet/cone. Perhaps I am mistaken.

Nathan

I take the difference to be as mentioned on the Beoworld Beolab 8000 page. There is also a different latch on the cable input, and this makes it easy to differentiate between the two

From January 2003, BeoLab 8000 was obtainable with new driver units giving extra bass at low levels. While not delivering as much as a