The present invention relates to a multiple channel earphone of small volume. In the earphone structure, a chamber tube with an adjusting hole or a set of adjusting holes is provided. The sound pressure of the chamber tube is naturally released without affected the performance of the main chamber sound field. When the external speaker connected to the chamber tube generates a large sound pressure, the sound pressure released naturally by the adjusting hole or a set of adjusting holes is increased accordingly, so that the sound pressure produced by the external speaker connected to the chamber tube is controlled by the main chamber.