Equipped with 40mm neodymium drivers at 58-ohm impedance, the SMH-1000 headphones are designed to be loud enough when attached to low powered devices such as mobile phones and MP3 players, yet robust enough to handle studio headphone amps without distortion.The over-ear, closed-back design is intended to help block unwanted outside noise, which is useful in professional field recording and studio monitoring scenarios where isolation is critical.