I am really happy with the sound quality of the RE Zero. The bass is much improved over the RE 0, but still maintains the clarity and distortion- free quality that the RE 0 has. Everything else about the sound quality is the same if not better. The build quality is very solid, and the gunmetal finish is very good looking. These headphones are great for a variety of genres, and I listen to everything from Alternative to Classical music. Meany headphones have trouble portraying the complexity of large scale orchestral pieces, but the RE- Zeros handle everything just fine. The 16 ohm impedance allows for easy use with portable players like i-pods, and I see no need for a portable amp when you are on the go. The adapter that everyone complains about is actually smaller than I thought, and is not a problem for me at all. Lastly, you cant beat the value, for an IEM that is consistently being compared to $300 IEMs, the fact that they can be purchased for less than $100 is unbelievable.
Pros - Extremly good soundstage(You'll hear every tiny detail), airy and clear, balanced bass.
Cons - COULD have little more bass, but up to your own taste.
For the price of 75 USD I think they're really worth every buck. The soundstage is huge(I dare say, as good as, or better than my Sennheiser HD 595's soundstage). The sound is crispy and airy just the way I like it. It have some bass, but less bass than for example Sennheiser hd 595. It could have more bass for bass-heavy genres, but then again it would not be that balanced. A earphone can not have both supreme soundstage and in additon extremly punchy deep bass. Re-zero have very good soundstage, crispy and airy soundsignature and decent bass. If you would like a pair of earphones with more bass, be ready to sacrifice some of the soundstage and/or experience another soundsignature.
Keeping this short as better people then i have written great reviews on this but im basically iterating what they find.
Excellent use for a mobile Rig. Sound isolation is much better than i thought. good on the train and still easy to take out quickly. can cause some hiss with my desktop rig but that is expected with the lower impedance. excellent for classical western and Indian music!