@bmoriarty
I used to own a series I Low B2. IMHO it worked really well with upright bass for both pizz and arco, within the cabs SPL limits. I did find the cabs SPL limits were barely adequate for big band and BG cover band settings. I found it pretty easy to clack the woofer's voice coils with string bass. Some will suggest using an HPF to fix this, but that sort of defeats the whole point of using this type of cab if you run the HPF up too high. I would suggest using a pair for louder gigs.
I found the cab relatively small but also fairly heavy and awkward to lift. I believe they changed the handles on the series II.
I did not find this design to sound perfectly flat or transparent, as the mid driver and tweeter was a weak point. My perception is the woofers seemed to dominate the tonal characteristics of the cab and they are tuned to emphasize extended low frequency response. I believe a more powerful mid driver was used in the series II, however, I would still not expect a lot of punch in the low mids because the mid driver is small and the crossover is high.
Low mids are handled by the woofers which have a very low efficiency rating. I tried to EQ in a bit more low mids, and the speaker really did not seem to respond that much. It did respond somewhat to higher mid range EQ inputs which produced sort of a nice fusioney grind with BG.
The Sensitivity rating for a Low B2 is 93dB and the RMS power handling is 350W. Recommended amp size is 300-500W.
I enjoyed using the cab as a monitor in relatively low volume settings, when I didn't bring subwoofers. I ran the Low B off an Aux so I could use it for bass and also mix in a little bit of vocals. It worked pretty well like this for jazz trio with vocals and a few horns.