I have a dream since months ago after read Golden-Ears AKG K550 review in last year to get this great stuff. And eventually I got it a few days ago with FiiO E07k USB DAC/Mobile headphone amp. Australia's greatest music gear producer AKG made this K550 model as people known it to reference headphone. By review of Golden-ears', frequency response is no clear and it is definitely close to reference standard.
Before it brings to me, my primary headphone was a little cheap model of K142HD. and it was enough to hear my lovely songs with FiiO E11 mobile headphone amp.
AKG K142HD - It brings to me a little bit pain for wearing in long time to fall in listening music by stiff cup cushion. Also its cup size not seems full-size. Weak assembly of each part of headphone makes me take it careful in all time. Of course it is for in-door only and open headphone,
K142HD sound is good for me (if it used with headphone amp) to listening my almost favor rock/metal and symphonic musics. Little lacking high frequency is comfort to make its volume to higher in safety level for my ear.
AKG K550 has super clear high frequency and really great-perfect fitting. Large ear cup makes no stress in long time listening music. I can't believe how closed headphone became a reference model, but it's true. Construction is durable. No air holes in outside of headphone shape. Simplified design and light weight becomes to great comfortable fitting.
First time of experience in listening music was so impacted to me. What a shiny sound ! I can feel like sound becomes to visually shines like a scene of movie. It was a perfection of sound that ever I never experienced before in headphones.
Behind of this perfection, there's also has dark side. referenced audio frequency hears actually boosted in higher frequency. So it makes me quickly tired than other headphones like boosted in lower frequency level. Like T-PEOS H-100 prototype, high frequency audio feels like to sibilancy distortion. It may cause of some people can't use this perfect headphone - Like there's no balance, not a good stuff - even it designed to reference.
One more negative, This is not for designed to going out. Not for on-the-go. But ironically AKG made it for mobile: K551 - just adjust cable length with iPhone compatible control unit. Actually K550 cable length is 3 meters and it could be possible carrying on-the-go with cable rolling up stuff. In case of using mobile headphone amp, my choice will be not so free: It will all in my bags and my shoulder also busy.
SO. I'm not recommend to use it for outdoor. Just listen your music in your quiet room with restful state.
Finally if I could make it score, I will give it 5/5 starts. Yes 100% perfect in price and performance, everything. And I recommend this stuff to "MUST HAVE ITEM" in your music life if you love to listening in detail.