In a headphone having a headband and two speaker units respectively pivotally mounted on the two distal ends of the headband, each speaker unit includes a speaker eccentrically positioned therein, an ear cushion covered on the front side of the speaker and having an eccentric opening, and a soft front covering the ear cushion and defining with the eccentric opening a sound chamber for enhancing the sound produced by the speaker and having sound holes for output of sound from the sound chamber to the user's ear.