They have a wide body and a short nozzle, so they don't allow a deep insertion (which reduces bass). Then they have a very odd tuning, unlike any other KZ. It's been described as W shaped tuning. But the sound comes across as tiny, thin, and hollow - like a cheap handheld AM transistor radio from the 70s. For literally the same price you can get the KZ EDR1 or EDR2 which has an excellent all-around consumer tuning (in other words, sounds good with most genres except maybe classical and orchestral). It's easy to drive with any source, sounds great with low-fi MP3 files and sources like cell phones, has nice tight responsive bass, juicy midrange, nice sparkly treble, good isolation, is built like a tank, and fits great (worn cable down). It's light years better than the ED4.