Summary The HE-400s work extremely well on portable devices but they can also be used most effectively with a high-quality hi-fi system. The HE-400 combines the advantages of a traditional dynamic design (such as 92.5dB sensitivity) and high output whilst offering a similar sonic signature (detailed yet 'warm') to the company's top-of-the-line reference models. Features HiFiMAN HE-400 - A New Level of Performance Trusted Reviews: Excellent! Easily Powered by Standard Amplifiers Planar-Magnetic Drivers Create Superior Sound Comfortable Lightweight Design with Special Earpads Striking Cobalt Blue Colour Design Driver: 50mm diameter dynamic drivers. Impedance: 35 ohm. Sensitivity: 92.5dB @ 1KHZ 1mW. Rated power: 30 mW. Frequency: 20 HZ to 35 kHz. Weight: 440g approximately. Details HifiMan HE-400 Headphones A breakthrough in both planar magnetic pricepoint and also in warm acoustic performance HifiMan's most recent headphone design provides the most affordable entry point for listeners seeking uniquely precise planar-magnetic sound quality. Easy to drive even direct from portable players or an iPhone a nice portable amp will add clean punch and improved definition for audiophile listeners. Sweet dark indigo colour stands subtly apart from the pack. HiFiMAN HE-400 Open Back Portable Orthodynamic Audiophile Headphones is another remarkable achievement from HiFiMAN. Compared to HiFiMAN's top-end power hungry planar magnetic headphones the HE-400 can be driven with lower-output headphone amplifiers. With low impedance and high efficiency they provide superb sound coupled with great comfort for the best possible portable audio experience. The high sensitivity of the HE-400 is remarkable for planar magnetic headphones meaning that they require less power and are easily driven with most headphone amplifiers. The HE400 utilises printed circuits result in an extremely light and responsive driver offering greater precision and reduced resonance compared to conventional dynamic .