Pros: Wide but balanced presentation, details without loudness,
Cons: finicky to amp
When I first got the K701, I had been using the Ety 4s so the bass was actually better on the 701s. They did sound tinny and shallow. I read that they needed about 400 hours of play to settle into the final character they will provide so I left them on along with a new tube amp for three weeks non stop. If they were going to fail, I wanted them to do it early in the warranty.
They did indeed respond both to moderate volume material and a more powerful amp. As I became more knowledgeable of the nuances of the sound, I started tweaking the cables, tubes and power cords.
I can say that while other headphones in the $250 range may have looks or a "wow"sound initially, I have always come back to the 701 for most of my listening. At this price range, I don't think you can find a better potential headphone to build a system around.
The audio quality of the headphone is based on balance. No one area of the sound is dominant. Some prefer a strong bass presentation and others prefer more highs be dominant. This headphone will earsmack you if the material presents it and your amp can deliver it. Otherwise the sound is distilled and smoothed. For acoustic and vocals, they do an admirable job. I enjoy early era progressive rock and acoustic rock with them. Anything more energetic and I have to change to the RS-1.
I am not a bass head but the 701s are bass lite. While the note is presented down to 35-40~, there is little weight unless the material highlights it. So listening to a bass groove will not stand out with the other music unless they are solo. But when listening solo, you can hear the pluck of the string by the finger, the leading edge of the note is solid and decay believable. The highs are a bit prominent. If your ears are young and treble sensitive, these could get fatiguing.
In deciding the value of these, keep in mind that you will need quality source material and amp to hear them at their best. Poor gear/material will be exposed. A solid state or hybrid amp is best suited for these because of their balanced presentation. I like tubes better but will cost more to get the same performance. AKG recommends 200 mv max. I'd recommend an amp with at least 500mw.