Pros: Deep sub bass, V sound signature. crisp highs. Carbon driver doesn't distort under pressure.
Cons: Most knock offs, Have to buy from Japan to get real ones.
I really loves these JVC HA-FX3X iem. I have been searching for something that can hit as hard in the sub bass as my desk 4.1 system, which I did find the Sony MDR XB950 over ear and the MDR XB90EX iem, but neither had the highs for the snare and high hat. I found the JVC HA-FX201 that has a great sound signature, but it begins to distort under huge sub bass pressure. (I make bass music)
I needed these because as the world becomes more cramped, it becomes less polite to blast sub bass into the neighborhood. Now I finally have a way of blasting my music that won't bug the neighbors and accurately recreates the sound I so love, without compromise. I ordered the newer HA-FX33X that will be here soon. I hope to review those as well.