So here are a few tech EQ words that are important to understand the bass window feature.
Shelf: can be high or low or whatever frequencies you want, it has a Frequency Value and then everything underneath or above is boosted of a decided amount (gain)
Example bass shelf at 40Hz with +4dB: everything underneath 40Hz is boosted at the same value, then after 40Hz, it goes back to flat.
This is the kind of EQ setting there's in most onboard Preamps and it's what makes the East so great to me, because all the preamps I've tested always had super low frequency for bass and it makes the sound very muddy.
Now there's another type of EQ setting it's called the Band EQ or Peak EQ:
Basically there's a frequency chosen to be boosted or cutted, and a bandwidth (also called Q) that's going to affect how you're affecting the frequencies around the selected one.
For example: 250hz band EQ at +4dB with a tight bandwidth: imagine a spike at 250Hz almost like a needle.
If you enlarge the bandwidth, you go from a spike to a wave.
So to come back to the East, the bass window settings are opening at 20 up to 80 Hz for the lower part of the bass window and closing at 40 up to 200 for the higher setting.
Lower setting controls when your bass window starts. High setting controls when it finishes.
(Technically there's an impossible spot like open at 80 and close at 40... )
So it means you have a band EQ for your bass with appropriate settings. You can go LOW at:
20 - 40 Hz (medium bandwidth) and then the knob you have on your bass for bass will control the gain of bass...
Or you can go super large bandwidth at
40 to 200 Hz, which comes into the lower mids area.
Or you can put a meaty solid bass setting without having sub-frequencies at: 60 - 100 Hz or 80 - 100 Hz.
But if anyone played with these settings could they tell us what settings they have chosen?
I hope my explanation was clear enough for you to understand this great East feature.
