I have been using beyerdynamic 990 Pro open back headphones for over 3 years. I mainly stuck with them for their analytical high end and neutrality which helped me with mixing.
But I decided to upgrade when music was just not giving me the shivers anymore... My ears had grown accustomed to analysis, not just plain listening. Music had become more of a job rather than music.
When I got the 660s2's I was quite excited. My initial reaction was a surprise at how different audio can sound. I spent my first hour with these headphones in complete confusion. My ears were confused listening to old favorites. But now 7 days later I can say these headphones are amazing. They bring out missed details, unbalanced mixes sound more obvious and overall listening to music has become extremely fun again. Music contains so much depth you can miss out on sticking to plain old headphones.
The only con is that this model is advertised as a boosted low end variant. In a techno heads opinion, it's quite flat amplitude wise, but the bass can definitely go way deeper. You will be able to hear extremely obvious changes when filtering 30-80 hz Subs. The bass is there but if you are into techno you will need a good amp.
