Having experience with the QC20 now for half a year... I'd like to suggest the following regarding the active EQ...
Upfront i must say i like to play loud often and am a bass lover.
The bass, in quite some cases is overwhelming. The short lasting, punchy bass sounds are generally bearable.
But the more constantly lasting, wide, open, full bass sounds (if that makes any sense) are a little much.
Also, in mid-rang (i don't know exactly, where the center frequency lies, i guess roughly around 3500 Hz) is also somewhat over-emphasized.
The engineers would know where emphasis is placed.
Also, i haven't noticed recently, but i have noticed it on some occasions that turning the ANC and active EQ on gave a little loss in detail.
I do like the active EQ since, when it is turned off, the volume of the bass, is a little disappointing.
I, personally, would suggest to lower the emphasis on the bass by like 15% and the mid-range emphasis by 7%.
My two cents. Thank you.