No - not knob size
Why do so many think their bass rig has to have 10 inch and 15 inch cabs (or other combination of driver sizes). OK there are some 3 way cabs with a mid-range driver and tweeter, and even two way cabs with bass and mid speakers, but a lot of bass players think that the ideal rig is a 1x15 with a 2x10 or 4x10. I think the theory behind this is that the 10's will carry the midrange where the 15's run out, and the 15 will go lower than the 10's.
But if you think about it the frequencies where the cabs overlap will be so much louder than the frequencies where only one cabs is effective as to render those frequencies virtually inaudible. Just by way of example take some Ashdown ABM cabs and the published frequency response (that is pretty vague to be honest):
ABM 115 37Hz - 2kHz 98dB 1W@1m
ABM 210T 75Hz - 20kHz 102dB 1W @ 1m
Not withstanding the fact that the 210 has a 4dB advantage in sensitivity it also means that 75Hz to 2kHz will be 7dB louder than 37 to 75Hz. That is one serious midrange hump!
Throw into the mix the possibility of phase cancellation where phase changes with frequency response at different frequencies for the different cabs and you have all the ingredients for a very unpredicatable sound.