...Edit: Also, in the case of the Berg, the Baer, and the Thunderchild, there is no 8/4 option... so, the impedance is what it is, and hence the efficiency and impedance differences become (IMO) a valid part of the comparison process. Again, just IMO there.
I think this is one area where Duke and myself took a different approach. With the 4 ohm TC112, Duke was trying to provide a single cabinet solution that would let you open up one of these micro heads and use all your available power into one small cab that would actually be able to handle it. A very good approach with a 3012LF based cab. (Duke, feel free to correct me if I'm wrong)
My approach was to deliver a cab that would handle the amp's 8 ohm power rating with good sensitivity, figuring that would sufice on most small to medium gigs. For players that need more volume on a larger gig, a stack of 2 ML112's presents a 4 ohm load to your amp and will put out a considerable amount of volume.
Haven't heard it with DB yet, but I'm working on that. I did hear Jay Terrien play a viola through the Valkyrie/ ML112 rig at NAMM and it was very cool indeed. He commented that he was hearing things in his playing he hadn't heard before. I take that as a good thing. Oh, and Steve Adelson stopped by with his Chapman Stick and was very impressed with that set up as well, so the cab does seem to work quire well for instruments other than electric bass.upright bass opinions please!!!

