A Low Frequency Horn of Small Dimension
A new loudspeaker horn is described. It is a low-frequency horn so folded as to utilize wall and floor reflections to improve the impedance match at the mouth. When operated in a room corner, the loudspeaker is capable of reproducing sounds of wavelengths over eight times the actual apparastus dimensions with an efficiency and smoothness of response comparable to theater "woofers" of several times the size of the device described. Since its size is approximately that of a console radio, it is applicable to living-room use. Because of its high efficiency, its use for small theaters and recreation centers is indicated. With suitable modifications for one or more larger size driving units, it would be capable of delivering the large amounts of power required for large theaters. Units may be stacked or clustered for outdoor use. With a frequency range of 40 to 400 Hz it is capable of fine quality when used with a suitable high-frequency unit, and since the high-frequency unit needs to deliver power only down to 400 Hz, it may be made quite small. The loading due to the horn offers a high real component of impedance for the diaphragm to work against, resulting in low diaphragm excursion and consequently the generation of negligible harmonic components compared with what would be generated by the same driving unit delivering the same sound output from a flat baffle. Motional impedance measurements show that the efficiency is good down to 40 Hz. The use of the corner, which is ordinarily waste space, and the arrangement of side baffles so that they, together with the room walls, form the terminal section of the horn, results in a simple compact structure and a considerable saving in material. In spite of the small size there is no sacrifice in quality.
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