+1I would very much doubt it's the cab. The TC112v2, 8 ohm, has a ton of low end. Authoritative, powerful, and definitely capable of dealing with low B. I can only imagine what the TC212 would be like.
I doubt its the cab as well. I also play keyboard bass in my gig with some fat sub low bass tones (well below low b on a bass) and my TC112 handles it with no problem.