Horn loading is frequently used in sound reinforcement to increase efficiency and directivity of high and mid frequency transducers. Low frequency horn loudspeakers are less common due to their large size. Increases in available amplifier power and thermal dissipation in transducers have led to widespread use of high power, low efficiency dual 18” bass reflex loudspeakers. However, some manufacturers and enthusiasts continue to develop and use low frequency horn loudspeakers for their high efficiency and subjective audio quality. In the fields of live event production and noise control, there is sometimes a perception, or “urban myth” that horn low frequency loudspeakers project or “throw” sound a further distance than direct radiating low frequency loudspeakers. This is either considered to be beneficial, or problematic depending on the context. Considering the relevant acoustic theory, it is not immediately apparent why this should be the case, providing the loudspeakers are level matched and of similar physical dimensions. Unfortunately, there is very little investigation of low frequency horns in previous literature to aid in providing a definitive answer. Measurements in this paper demonstrate that horn and direct radiating low frequency loudspeakers and arrays closely follow the theory, and the difference in propagation loss is within measurement uncertainty. The implication for noise control of outdoor events, is that bass loudspeaker size and type are not especially relevant factors, and focus should instead be on system/array design and site layout.
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