I don't think SRH1540 has recessed mids. Not really. I would say that they are just a bit in the background relative to the bass. I think the mid/treble balance is great on the Shures. In fact, sometimes I feel that they could use even a touch more presence or perhaps more attack in the highs, as the treble is quite soft/smooth sounding on the Shures and can sometimes get slightly lost behind the bass and low mids, which have more presence on this headphone than the treble.
I think the sub bass (<100Hz) is the only part of the frequency range where the Shures deviate significantly from neutral response and have a noticeable (and excessive IMO) emphasis. The sub bass can sometimes intrude into the mids to my ears, especially with bass oriented music - EDM, electronic, trance, etc. If the music has a lot of low bass content, I can't listen to the Shures at high volumes at all because the air pressure from the low bass simply becomes too strong for my ears to bear. At moderate volumes, the low bass doesn't cause discomfort, but excessive emphasis on the lowest notes can still be heard.
I think Shure engineers have messed up the tuning of the SRH1540 somewhat with that strong low bass boost, which may appeal to bassheads, but not to people like myself who are looking for a well balanced sound, with satisfying, but not overpowering bass. If the Shures had a few dB less of the emphasis, the headphones would have been almost perfect sonically IMO. In pretty much every other aspect of sound, the SRH1540 is fantastic to my ears - wonderful balance from mid bass through to upper highs with no odd dips or peaks anywhere in the response, great sense of space and separation that rivals good mid level open back headphones, excellent dynamics, superb detail retrieval in the mids, great refinement and clarity across the entire range...
I think the mids are actually where the SRH1540 shines the most. Even though it can get a little lost behind the low bass boost at times, the quality of the mids is simply amazing - the timbre of human voices, especially male ones, is spot on and that coupled with excellent detail retrieval, including micro detail, really allows me to feel like I am there with the singers quite often and more often that with any of my other headphones actually, even HD800. That's right. I am not saying SRH1540 has better mids than HD800. In fact, I think HD800 mids are even more detailed and refined. However, the tonal balance of the HD800 is less natural due to emphasis on the treble around the 6 kHz range and a dip in the presence region (2-4 kHz) that makes vocals and many other instruments sound overly distant and unnaturally thin at times. SRH1540 doesn't have this issue with tonality and this allows it to often sound more natural than the HD800.
Overall, SRH1540 is the best sounding closed back headphone I've heard. Its only downfall is that excessive low bass emphasis IMO. In most other aspects of sound, it is clearly ahead of other closed backs I tried, such as Focal Classic, NAD HP50 and ATH-MSR7, and sounds closer to an open back headphone in regards to air and overall sense of space than any of the others. It's still a bit behind open backs such as HD600 or K612 Pro in regards to openness and sense of space, but not by a lot.