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Feb., 1930] LOUD SPEAKERS 169
less favorable for the use of the baffle speaker than it is in small theaters. This is due to the fact that as the required acoustic power increases, the difference in the number of speakers necessary to carry the power becomes greater and the additional power capacity of the amplifier becomes more expensive. Consider for example a theater having a seating capacity of 2250 and a volume of 460,000 cubic feet. From the curve in Fig. 2 such a theater would require an acoustic output from the loud speakers of about 2.3 watts. Horn type loud speakers used in this theater would require an amplifier capable of delivering 9.25 watts, and the number of horn type speakers required to carry the power need not in general be greater than in the case of the small size theater discussed above.8 On the other hand baffle type speakers would require an amplifier capable of delivering 92.5 watts and at least 15 speakers to carry the power. The power capacities of the amplifiers are still in the ratio of 10:1, so that for the above assumptions it would appear that fifteen baffle type speakers must be procurable at a cost less than that of two horn type loud speakers by twice the cost of the horn speaker amplifier. The cost of the baffle speaker for large theaters must therefore be considerably less than that justified for the small theater installation.
CONCLUSION
In this paper the performance characteristics of baffle and horn type loud speakers have been discussed in a very general way and the bearing of certain inherent differences between the two types upon the economy of theater installations has been illustrated. It is, of course, impossible to draw any precise conclusions from such reasoning since baffle and horn type speakers may each vary considerably in their performance characteristics. The comparative values assumed in this paper, however, are fairly well substantiated not only by the better existing designs but also by theoretical consideration of possible future improvements. For example, it may be quite possible to improve the efficiency of existing baffle speakers, but on the other hand a considerable improvement in horn type speakers also seems practicable. The same may be said of the power capacity of each type. Other factors such as the use of several loud speaking receivers on the same horn, the effect at low frequencies of using a plurality of
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8 In some cases where distribution difficulties are encountered as many as ;three or four horns have been used in theaters of this size.