Thought I'd share some impressions on the K540, since I auditioned them today alongside the K518LE.
As a tl;dr: The K518 beats the K540. Read on if you like.
As a semi-open can, I wasn't surprised to ear a pretty big soundstage from the K540. Nice imaging characteristics and sense of depth. The sound, however, kinda made me raise my eyebrows. I was hoping for some good mids from these cans, but unfortunately they came out quite recessed. Even though the soundstage was set up quite well, Clair Marlo (in my test track) was drowned in the soundscape and her voice lacked humanness and presence. The mid highs were also "plasticky", making string accompaniments sound fake and synthetic.
And I'd like to shed some light on the idea that these cans are bright - they're actually quite veiled in the upper treble range. What makes them seem bright is a high amount of sibilance. These headphones are REALLY sibilant. Using the Bass boost 1 on the E7 helps relieve the excess sibilance, but the mids suffer quite a bit. Otherwise, there is little sparkle in the treble, making the music sound somewhat detached and disengaged.
The lows, however, were quite good. There was presence and punch, but for some reason it felt a little messy for me. I don't know if it's because I'm used to the bass characteristics of the K242 - but I didn't have the same qualms when I listened to the K581... it was just with the K540.
Overall, I was quite disappointed with the K540. Priced 3,000Php (~60 USD) above the K518, it really didn't feel worth it. The plasticky build of the headset and its tendency to wind up lopsided on your head (one band extended further than the other) was another turn off for me.
So yeah, I didn't really like the K540. YMMV, though - but these are my impressions.
