For comparison, I have here the Audio Technica ATH-M50 (Over Ear, therefore in a completely different league) and the supplied Sony MH750 my Xperia Z3 Compact (about 8 euros). I compare the RE-400 see the sound quality with the two rivals look bad against both.
Both in the bass, as well as in the Klangbuehne (even against the MH750) are considerable weaknesses noted. The sound of the RE-400 sounds flat and straight. You experience any depth and can differentiate difficulties between individual instruments. Only in the heights, the RE-400 shine a little and strikes the MH750 significantly. Especially with Klavierstuecken can convince the RE-400. However, once another instrument is added is playing extremely unpleasant to the ear. The deeper you go (RnB, techno, house, ...), the more boring the sound image. The basses have no pressure and are sometimes not perceived.
Due to the many reviews on the internet I would have expected more significantly. I can not guarantee buy recommendation for the RE-400, and must even at this price advise against the purchase. Here one is far better served with other Kopfhoerern.