HiFiMAN RE400 review: specs and price

The device comes with its own special case or pouch, which is useful for safe transportation.

The in-ear device is ultracompact and lightweight, with little or no interference with earrings, spectacles, hats, or hairstyles. It is inserted in the ear canal itself and blocks out a lot of environmental noise. It has stronger bass tones and is unlikely to fall out of the ear.

An L-shaped plug is better if the jack is on the left or right side of the device, so that the cable isn't bent, and is less likely to break when the device is in your pocket.

The lowest frequency at which the device produces audio. The lower the low-frequency response, the stronger and juicier the bass.

The highest frequency at which device produces audio. The higher the high-frequency response, the clearer and crispier the treble.

The device sits tightly in place, creating an acoustic seal which reduces background noise and prevents your music from leaking out.

Devices with a higher sound pressure level are generally louder when supplied with any given audio source.

Impedance is the device’s electrical resistance to the current being pushed through it. The lower the impedance, the easier it is to get higher volume and requires less power.

Devices with neodymium magnets are lighter and more powerful than those which use ferrite magnets. They also have more bass and clear high notes.

A standard 3.5mm male connector is suitable for use with all MP3 players and computer sound cards.