SMALL DIMENSION LOW FREQUENCY FOLDED EXPONENTIAL HORN LOUDSPEAKER WITH UNITARY SOUND PATH AND LOUDSPEAKER SYSTEM INCLUDING SAME

摘要

Abstract of the DisclosureA small dimension low frequency loudspeaker has afolded exponential horn which provides a unitary curved soundpath from an electroacoustic transducer at the throat of thehorn to a volume into which sound is radiated at the mouth ofthe horn. The length of the horn is such that, at an exponentialrate of expansion between the throat and the mouth, the mouth,when it is bounded by at least one planar surface, such as afloor, a ceiling, and/or walls of a room, has adequate area toenable reproduction of low audible frequencies. An illustrativeembodiment of the low frequency loudspeaker has an effective lowend cut-off frequency of 55 Hz. A loudspeaker system, includinga low frequency loudspeaker as well as midrange and high frequencyloudspeakers and an LC crossover network, is also disclosed. TheLC crossover network includes an autotransformer which not onlyserves as a component to determine a crossover frequency butwhich also boosts the electrical signal that is input to theelectroacoustic transducer of a less efficient loudspeaker. Theautotransformer increases the output of the less efficient loud-speaker and accommodates its use with more efficient loudspeakersso that the overall loudspeaker system operates at optimum effi-ciency. An illustrative embodiment of the loudspeaker systemaffords 108 dB SPL output at one meter with one watt input whichcorresponds to about 20% overall efficiency. The smoothness ofamplitude response over the range of audible frequencies that isnecessary for high fidelity sound reproduction is improved byinclusion of peaking circuits in the LC crossover network ofthe loudspeaker system to enhance amplitude response in theregions of crossover frequencies. Side wings are additionallyprovided to eliminate cavities at the sides of the loudspeakersystem which would otherwise cause deterioration of smoothnessof amplitude response.