The mixer EQ has "fixed" frequencies and "Q"
Here is a pink noise spectrograph with the mixer EQ set "flat"-
And here is the same audio signal with the EQ set to full cut in all three frequencies-
And again at full boost-
Noting the frequencies affected:
The bass is a shelf filter, rolling off at about 300. Range is +/- 15 dB.
The treble is a shelf filter, rolling off at about 5K. Range is +/- 15 dB.
The mid frequency is a bell filter based a little below 3K, Range is +/- 12 dB.
Also of interest is the effect on RMS and peak levels.
My conclusion- I use the low and high frequencies often in mixing for subtle adjustments. The limits of the range of boost/attenuations mean they arent really for "big moves"
(IE turning down the low freq. to max cut isn't a HPF for example)
I dont use the mid range much. Its utility is limited due to its "fixed" frequency and "Q"
(* Suggestions have already been logged to update this in the future. Suggestions include adding a sweepable freq. range function and adjustable Q.)