HD 660S

Great clarity of sound, kinda narrow soundstage, but for 350$ they are great value.

I was surprised that it genuinely excelled in every way. Quality of sound is incredible. It’s so much more lightweight and comfortable than anticipated. My first pair or Sennheiser’s blew me out of the water. I must say, I’m officially a huge fan.

For me this was the first set of headphones from the 600 series, and I have no regrets. I have several 500 series and they sound great don't get me wrong, however there's a different kind of change when switching to the HD 660s. particularly for me orchestral tracks sounded more vibrant and cleaner, what was once drowned out by other instruments is now very clear. I in particular enjoy listening to movie soundtracks. Movies like Krull are an excellent example of the power of the HD 660s because of how lush and dense the soundtrack can be. Particularly tracks like "Ride of the Firemares" and "Battle on the Prarapets" where there's a large orchestra performing a very vibrant and active piece, things like the triangle are no longer drowned out by the horns and strings, it's very clear. Things like the the string instruments now have a clarity to them that feels even more realistic than before. it's really unreal the clarity you get. All that mixed with the fact that they're only 150 ohm with a higher sensitivity, makes it easier to drive than some of the other 600 series headphones. I personally I use a FiiO M11 with the HD 660s with the balanced output, and it sounds fantastic. I really can't recommend them enough or describe it in enough detail, it's something you only truly understand of you hear them for yourself.

I've used them only a little since I've only had them five days. My usage is on computers for online collaboration broadcasts, so my bias is as an amateur.

The sound quality seems very nice. If there is one thing to work on is how to improve comfort and fit for people with big heads and ears. The are pretty tight for me. They will also have my ears sweating and sore within an hour!

First headphone I invest good money. Don’t know much but I enjoy the open back and the change in quality is clear.