Yea the bass presentation in Q40 is pretty much SPOT ON for my taste, the ideal quantity vs quality ratio, anything more and it'll start to impact on mids/highs too much. It's also got the right "shape" that produces the punchy impactful bass across the whole range, it actually sounds deeper than what the graph would suggest, very deep bass (now talking 20~40Hz or so range) comes through with great authority, it gives that "feel"-the-deep bass tickling ear feel especially paired with ZO without overhelming. But yea Q40's bass is very well balanced in deep vs midbass and among serious basshead cans it's not the very punchiest but far from the least punchy, it's a lot more closer to the punchiest bass available again the subb vs midbass presence is just spot on, balanced, I can't say it's either midbass or subbass focused, the whole range comes through as the way the producer intended it to be.
Q40 is the first headphone which I don't have to EQ at all, all the other headphones I've bought/tried I've managed to improve by EQing, Q40 sounds best with EQ disabled as long as I use WASAPI in foobar2000, turning soundcard EQ on means I have to run with DirectSound output which leads to slightly worse sound quality so therefore it's always ideal for me if I could find headphones with exactly that response I personally like and Q40 is VERY close to the ideal frequency response balance for me. I only feel that in the lower mids (300Hz ~ 1kHz) I'd welcome ever so slightly more forward mids, the way it currently is balanced it actually sounds quite neutral there but I personally would optimally even prefer very slight colorisation, say 2~3dB boosted lower-midrange over the upper-mid and highsrange as it gives that fullbodied midrange and warmth I like. Apart from FR response the soundstage could obviously be noticably improved still for my liking, soundstage size (especially width) is probably it's biggest "weakness" it's about average closed headphone performance but depth and separation is relatively good for a headphone with such a big bass response.