LOW FREQUENCY FOLDED EXPONENTIAL HORN LOUDSPEAKER APPARATUS WITH BIFURCATED SOUND PATH

摘要

A low frequency loudspeaker apparatus includes a folded exponential horn which is divided to provide a bifurcated curved sound path from at least one electroacoustic transducer that is positioned at the throat of the horn to a volume into which sound waves are radiated that is located at the bifurcated mouth of the horn. The mean length of the folded exponential horn is such that, at an exponential rate of expansion between the throat and the bifurcated mouth, the area of the mouth is adequate for reproduction of low frequencies in the audible range. An illustrative embodiment of the low frequency loudspeaker apparatus has an effective low end cut-off frequency of 38 Hz. and affords 99 dB SPL output at three meters with one watt input which correponds to about 20% efficiency measured in free space. Presence of a single boundary surface, such as a stage floor adjacent the mouth of the folded exponential horn, improves amplitude response by 3 to 6 dB.