Abstract: The present invention comprises an L channel speaker unit which produces an L channel signal; a R channel speaker unit which produces a R channel signal; and a center speaker unit which is placed between the L channel speaker unit and the R channel speaker unit and which produces a −L channel signal and a −R channel signal. For speakers mounted in an automobile described above, the L channel speaker unit and the R channel speaker unit are placed in the front center of the driver seat and passenger seat of an automobile, and the horizontal vibration axis is in a direction pivoting in a direction from the direction of motion of the automobile, and a vertical vibration axis is at a prescribed angle incline in the direction of motion of the automobile.