Abstract: The present invention relates to a speaker device or the like capable of stably providing desired directivity provided by a combination of omnidirectionality and bidirectionality down to ultra low frequencies. A speaker (22) is attached to one end face of a speaker box (21) and a sound wave radiation port (23) in a circular shape covered with acoustic resistance material (24) is installed at other end face thereof. The sound wave radiation port (23) is for radiating air vibration produced by a rear face of a speaker diaphragm to outside as sound wave and an axis penetrating the center extends in a direction of a principal axis (reference axis) of the speaker (22). A low pass filter is constituted by acoustic resistance and acoustic mass of the sound wave radiation port (23) and acoustic mass provided by air in the speaker box and a directivity is provided by utilizing group delay time in a pass band of sound wave radiated from the sound wave radiation port (23) via the low pass filter.

Abstract: A loudspeaker unit comprises a loudspeaker box, a first loudspeaker attached to a front panel of the loudspeaker box, and a second loudspeaker having the same diameter as that of the first loudspeaker and attached to an upper panel of the loudspeaker box. The first loudspeaker is driven in a positive polarity and the second loudspeaker is driven in a negative polarity. Driving voltages E1 and -E2 respectively for driving the first and the second loudspeaker are optional voltages meeting E2/E1<1. The sound pressure of sounds radiated by the second loudspeaker is lower than that of sounds radiated by the first loudspeaker. The directivity factor of the synthesis sound pressure of the first and the second loudspeaker at a sound receiving position with respect to the 90.degree.-direction is equal to the product of the directivity factor D(90.degree.) of the loudspeaker and a value (1-.alpha.) smaller than one. Accordingly, the output sound pressure of the loudspeaker can be reduced regardless of frequency.