AKG K 540 - Reviews
Pros: Comfort, bass, treble, vocals.
Cons: Midrange sounds bad for the price, too much sibilance, sounds really thin.
Hi guys so this is my first review ever on this site. Keep in mind that I'm no audiophile by any means.
The only cans I owned before were the Philips SBC HP400 and a cheap $10 wolfgang pro headphone.
I decided to buy a high quality headphone on one day, because I was tired of the comfort issues I had with my previous headphones, and when I searched for a good headphone, I heard a lot of great things about the K540, like they were worth $300 and you could hear every single layer of the track and things like that.
But all of that was false, and you're going to read why.
I own the K540 for 11 months now, and they have well over 500+ hours play time. 
Lets first start of with the packaging:
The packaging is nothing special, they come in a cheap plastic box with a 6.3 mm adapter.
Build quality:
To be quite honest, these feel really cheap. On the first day that I bought them, my brother tried them out, but he accidentally put them on reverse and the headband broke. Really, it just broke because he didn't put them on the right way. I was fortunate enough to get a new pair though.
I have a average sized head and small ears, and these fit really comfortabely around my ears. Even after 2 hours they're still very comfortable, but they can get a little hot though after a while, just a little.
Isolation and sound leakage:
These isolate a very tiny bit, but definitely not enough if you don't want to hear other people talk around you. You can cleary hear conversations in the living room when you're having these on, but that's probably because they're semi-open. Speaking of the semi-open design, these leak pretty little, if you're having your music on normal volume settings. But if you play them louder, let's say on 50%+ they'll leak quite a lot.
Sound quality:
(My main genres are rap/hiphop, and very occasionally some dubstep.)
Straight out of the box these things sounded BAD, you could almost literally only hear sibilance from these. After about 60+ hours they settled in completely, and sounded a lot better than first, but they still don't sound right imo. The sound signature in general is warm.
Lets first start of with the good:
Cymbals and vocals sound pretty realistic, like they should be from a can of this price range. Treble sounds pretty good and clear, but can be really harsh sometimes. Detail is also quite good, but nothing special, you can hear tiny soft words and things like that in the track occasionally. Bass is fairly tight, controlled and can go quite deep, but it doesn't over power the mids and highs.
And now the bad:
These are definitely some sibilant cans, which is REALLY annoying, even on 320 kbps mp3's. They definitely don't have a full sound to them, they sound really thin. Midrange is really thin and the clarity of the midrange is just bad for the price range, even though I'm no audiophile. Instrument separation is not good, these things sound jumbled. Soundstage is decent for a semi-open design.
I wouldn't recommend these to anyone who dislikes thin sounding cans, sibilance, harshness, bad midrange clarity and bad instrument separation in general.
I still give them 2,5 stars because of their treble, bass and comfort.