Originally Posted by Youngspanion
And we are dealing with just the volume of the specific frequency range that the control? I see on the right side of each graph a dB sign with a number with nothing or a number with a negative sign ( -). with 0 being the 'Center'. Is this right?
It's not just the center frequency that affects the sound of a given tone control, it's the "Q" or width of the filter.
A really narrow, sharp slope is used for something like a feedback buster, because you want to surgically cut out just the feedback frequency, and leave the rest of the spectrum alone.
On a bass amp, wider filters are used. So when you boost at 360Hz, you'll actually affect a broad band of frequencies, starting to ramp up an octave or more below, and tapering off again an octave or more above the center frequency. The wider the filters are, the more the bass, mid and treble controls will overlap and interact with each other.
Markbass deliberately chose a higher than average center frequency, presumably to stop the low end from sounding too tubby when the mid control is pushed. Depending on your cabs, your basses and your taste, you might hear that as a having a nice "tight" low end, or you might hear it as lacking "punch".
This is why variable midrange controls have become so popular, because you get to hone in on the exact frequency range you want to affect.