PURPOSE:To raise the sound pressure level of a low frequency band without damaging the dynamic range of a driving amplifier and to set a reproduction band to be wide and flat by providing the radiation hole of a port provided for a chamber whose capacitance larger in a place approximated to a floor or a wall surface and providing the radiation hole whose capacitance is smaller in a detached place. CONSTITUTION:The radiation hole of the port 7 provided for the chamber 5 whose capacitance is larger in two chambers 5 and 6 is provided in the place approximated to the floor and/or the wall surface. Reflection from the floor and the wall surface is used for a sound wave radiated from the port 7. The radiation hole of the port 8 provided for the chamber 6 whose capacitance is smaller is provided in the place detached from the floor and/or the wall surface. The sound wave from the port 8 is not influenced by radiation from the floor and the wall surface. Thus, the sound pressure level of the low frequency band can be improved and the reproduction band can be made wide and flat.
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