Warning: my vocab sucks, so i'll try to explain best i can. In a briefest of brief reviews:
Source: 44Khz/16-bit wav files (straight off CDs I own, no downloads) and 320kbps MP3 of the same WAV files
Sound Card: Sound Blaster Z (upgrading to ZXR this Saturday, 3/22.2015, thank you NewEgg)
MP3 Player: iRiver IHP-140
At low-moderate volumes: 9.5/10 (90% of my listening will be done at these levels)
At high volumes: 7/10 (10% when I get carried away by a tune)
Reasons for such score: As long as you keep the Shures at low-moderate volume they shine. Great treble presence, bass, vocals and mids are present and forward. If you are coming from and compare them to very mid-forward headphones such as HD 598 you may think that the mids here are ever so slightly recessed, but on their own hard to tell.
Very very subtle U-curve to the sound but it's what makes the headphones fun with everything. I feel the U-curve becomes more prominent the higher the volume goes and thus the lower score at really high volumes.
At high volumes I feel the higher frequencies are stronger while the bass isn't able to increase in the same proportion. Thus it ends up being a bright headphone at volumes over 70%. Also there is audible distortion on bassier tracks (such as Jay-Z: Empire State of Mind) at louder volumes. People have responded in the forums about what causes it, but for me, i think the driver just can't handle it. It gets pretty fatiguing pretty fast at loud volumes (for specific tracks that might be a little trebly to begin with).
The sub-bass also doesn't slam you at higher volumes like it does in the M50s or the A900x. But the soundstage and overall presentation of sound is a league above what the A900x and M50s can produce. Don't get me wrong for the price both are great, but if you do move up to the Shures, you will get better of almost everything. Not everything mind you (that would be the perfect headphone, and like the perfect woman, doesn't exist). But what is perfect to you? That's all that matters.
Games/Movies: 9/10. Loved it. Sound stage, bass, clear and present treble and mids
I also own the HD-650 and these are easier to drive and thus sound better with amps, MP3 players and sound cards that don't do 50+ Ohm headphones well. I will be getting the Sound Blaster ZXR because it has a high gain mode and a different amp than the one in Sound Blaster Z and test them out side by side again. But off the equipment I have right now I feel that the SRH1540 delivers more.
I may look to get the HD 700 since the SRH1540 covers all my
basses (pun intended) in most genres. And I may want a specialist headphone for orchestral and vocal tracks. I may forgo the bass of the HD 650 and go for a less veiled sound (from what I've gathered on the forums) in the HD 700.
Tracks used for the review:
Jay-Z: Empire State of Mind
Pearl Jam: Alive
Def Leppard: Animal
Michael Jackons: Billie Jean
Bruce Springsteen: Streets of Philadpelphia
Morgan Page: Believe (fav track from that album)
Frank Sinatra: Fly Me To The Moon
Ludovico Einaudi: Divenire (from the album "Live in Berlin")
Pink Floyd: High Hopes
The Lord of the Rings: Concerning Hobbits (From "Fellowship of the Ring")
The Shawshank Redemption: Compass and Guns
Kings of Convenience: Misread, and Gold In The Air Of Summer (two from one of my all time fav bands)
http://grooveshark.com/s/Gold+In+The+Air+Of+Summer/6GBDIh?src=5