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THE LOUDSPEAKER
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high amplifier distortion. In addition to this distortion, the relatively great voice coil current of the loudspeaker produces a magnetic voice coil flux that is large in relation to the flux provided by the field. The over-all result is truly excessive distortion when compared with the first commercial 16-mm sound projectors.
Fortunately, loudspeaker design has improved considerably due to the availability of Alnico V since World War II. This material makes possible the same flux density as Alnico III magnets of more than 4 times the
Fig. 114. Western Electric 755 A loudspeaker mechanism. One of the finest single-unit loudspeakers manufactured. A significant improvement in performance will usually be obtained with all better grade 16-mm sound projectors if this loudspeaker is substituted for the one presently used. Power handling capacity: 8 watts. Frequency range: 70-13,000 cps. Coverage angle: 70 degrees. Voice coil impedance: 4 ohms. Efficiency: At 30 ft. on axis, a level of 81.5 db above 10-16 watt per sq. cm. at 8 watts input. This level rating is based on a warble tone covering 500 to 2500 cps. Over-all diameter: 8|". Depth over-all: 3$". Weight: 4 lb. 12 oz. Baffle hole diameter: 7". Mounting holes: 4 equally spaced on 7f" circle. Speaker enclosure recommended: 2 cubic feet.
weight. The new RMA standard 4.64-oz. magnet, for example, provides the same flux density as the former 20-oz. magnet of Alnico III. A good design of direct-radiator loudspeaker is the Western Electric 755A (Fig. 114), that is rated as 8-w. continuous rating; this loudspeaker weighs