content: I wouldn't say that open-back headphones are superior to closed-back and/or semi-open-back headphones.  All three types have cans ranging from terrible to absolutely amazing. Logically, a good pair of closed-back headphones will outperform a pair of open-back ones, if they're rubbish. I have compared my AKG K240 MKII (semi-open) to my K550 (closed) and a friend's HD600 (open). I'm barely even using my K240s anymore, because the K550 just sound better in my opinion. A lot of reviewers commented on how the K550 is "the most open sounding closed-back headphone" and I can confirm that. I was stunned by how similar the HD600 and the K550 sounded.  They have an amazingly wide, airy soundstage. Since the K240 doesn't isolate noise for shit (might as well call it open) I've bought myself a K550 for two reasons:  Learning for exams is hard, if there's half a dozen kids playing football in front of our house. Gaming. I have a mechanical keyboard and would prefer not to hear it while playing games where I rely on my ears to find enemies.