Journal of the Society of Motion Picture Engineers (1930-1949)

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618 Louis MALTER [J. S. M. p. E. all frequencies below 300 cycles and above 4000 cycles exerts a negligible effect upon the understandability of speech. Since, on the whole, the response of the two speakers between these limits is the same, we would expect the understandability to be the same. This is what is actually observed. However, the characteristic frequencies of the speaking voice lie below 300 cycles. They center around 125 cycles for the male voice and around 250 cycles for the female voice. It is these "fundamental" frequencies which give to each speaking voice its individuality and distinctiveness. A lack or deficiency of the frequencies below 300 cycles will rob the voice of these characteristics. This accounts for the superiority in naturalness of speech reproduction on the directional baffle type loudspeaker. The response of the directional baffle type speaker, between 100 and 300 cycles, is considerably greater than that of the horn type speaker between the same limits. This is particularly true below 140 cycles. Around 100 cycles the difference in response is around 12 decibels. The reproduction of music is also adversely affected by the deficiency in the response below 300 cycles. Music reproduced on a horn type speaker lacks the fullness and depth apparent in the reproduction by the directional baffle type speaker. The complete reproduction of the lower register instruments is impossible on the horn type speaker. The result is that music loses its real quality and retains merely its melody. This is particularly true for music of a symphonic nature. In a recent paper2 certain statements are made in a discussion of horn and cone (or baffle) type speakers. The cone (on baffle) type speakers referred to in that paper are of a type wherein cones are set in a flat baffle, a type which is much less widely used than the directional baffle type speakers. Some of the claims made for the horn type loudspeaker are not borne out by our experiments. Thus it is claimed that the horn type loudspeaker and flat baffle type of loudspeaker are equally satisfactory as regards frequency characteristics. This may be true in theory but tests of actual devices as used in commercial practice show that the upper and lower cut-off frequencies of the flat baffle type of loudspeaker, which coincide approximately with those of the directional baffle type using the same cone, are much more widely separated than those of the horn type loudspeakers. 2 BLATTNER AND BOSTWICK: "Loudspeakers for Use in Theaters," /. Soc. Mot. Pict. Eng., XIV (Feb., 1930), No. 2, p. 151.