Long time lurker here.
I've owned the K7XX for a while now and I'd like to share my brief impression with them. I am hoping someone can address my concerns.
I've been using them on daily basis since I first got them back in July. After running them through plenty hours of pink noises and playing music for almost 150 hours in foobar, I've decided the sound has mostly settled down (since 50 hours in) and should it changes, it'd only be minor technical improvement not the signature itself.
I'd like to compare it to my Audio Technica AD700 because that's what I have enjoyed immensely before I decided for an upgrade. Needless to say, what peaked my interest in AKG was their praised soundstage and high range frequency. You've probably guessed by now that I'm disappointed with them. I'm running my headphones straight from the Aune X1s (another disappointment of mine).
Tonality wise I'd like to describe the K7XX to be slightly warm with good extension towards the low frequency, however I can only describe the high to be present but without the sweetness of the AD700. Overall the K7XX sounds full to me but doesn't have that deep extension into the highs like the AD700 does, making it quite boring.
Soundstage is again a disappointment compare to the AD700. I can distinguish each instruments or elements better with the K7XX but somehow they just sounded more congested to me, unlike the airy presentation of the AD700. I've read other owners described the soundstage of AD700 to be artificial but I like what comes out from them. Whereas the K7XX just doesn't have the width, depth or height I have anticipated for.
I should note that the K7XX is definitely the more technical, faster sounding headphones, showing more details than AD700. But that did not help me enjoy my music that much either. I suppose this is what analytical sounding means. I was expecting the K7XX to be an overall upgrade coming from the AD700 but sadly that is not the case for me. Should I have a second chance, I'll most probably pick up the AD1000X instead.
Now if anyone can compare their K7XX with the AD series from Audio Technica, I will be very pleased to be proven wrong. Furthermore, please tell me if I could benefit from a dedicated amp as I suspect that is an area I can improve on.