The extra mid-lows from the B likely comes from the extra 4 power tubes- it has WAY more balls. But, Bs were known for having more bottom end. I guess I was referring to the upper mids. When playing these in my band the B is huge & thick, where the C has a great tone but it totally overpowers the mix. My vocals almost go away. I had the pots set more or less the same here & I agree with some tweaking it could be normalized better. When I've done this, as well as slaving the power section to normalize that, the main difference between the tone of the two amps comes down to that upper mid presence.
Note I did not pull deep in this vid.
Slaving power section-
https://youtu.be/cQjjAtewUzQ
In the band mix-
https://youtu.be/gvy4BroOqMM
Racer, I agree the SR has more upper mids than your average Mark. And no honk. That said, compare it to this factory IIC+ DR I used to have. Maybe there's just something to Doug West's NO-EQ ideas. IMO they have better tone, presence & sustain all else equal than GEQ models. I know a couple guys with IIB 60 watters that do this too. One of them is loop modded and it crushes!
https://youtu.be/G6zI-fVggTo?t=291