Abstract: A headphone set has at least one speaker section. The speaker section includes a baffle having at least one sound emitting hole, a surrounding wall formed on the baffle so that the surrounding wall protrudes from the baffle and surrounds the sound emitting hole, a speaker unit installed within the surrounding wall and having a first surface to face the sound emitting hole and an opposite second surface, a unit case provided as touching the surrounding wall and covering the second surface of the speaker unit, a first cavity existing as enclosed by the unit case and the second surface of the speaker unit, and a housing provided as touching the baffle and covering the unit case, a second cavity existing as enclosed by the housing, the unit case, and the baffle.