International projectionist (Jan-Dec 1947)

VOLUME XXII FEBRUARY 1947 NUMBER 2 'Quality' vs. 'Pleasing' Sound Reproduction By J. MOIR IT IS common experience that the majority of the public prefer tone controls in the position that minimizes the "top" response. Discussion of this practice has probably occupied more time at engineers' "sound quality" lectures than any other single problem. The generally accepted explanation is that the public does not like the amplitude distortion introduced by the average sound reproducer, preferring the lesser evil of "top cut." There can be no doubt that the effects of amplitude distortion, surface noise, sideband splash, etc., are minimized by "top cut," but a feeling that other reasons, possibly more fundamental, may be behind such a universal practice led the writer to consider other possibilities. To put the problem into its proper perspective we must have a clear understanding of our target! Is it the engineers' job to produce "pleasing reproduction" or a perfect reproduction of the studio performance? Public Prefers 'Top Cut9 Purists will probably consider as rank heresy the implied suggestion that "pleasing reproduction" and a "perfect reproduction" are not the same thing; but the writer cannot see any reason for agreeing with this view. To do so would imply that the present range of musical instruments had reached perfection. Irrespective of the engineers' decision on this point, the public, knowing little of the fundamentals involved, will choose to have the "most pleasing" reproduction whenever the engineer places the choice in their hands. The public, having given the answer to these problems in no uncertain voice, and as it is certainly not the answer an engineer would expect, we must make an honest endeavor to decide whether the particular choice has been made because of defects in the engineering or because of some more fundamental factor. It cannot be disputed that amplitude distortion leads to a tendency to restrict the frequency range, if that facility be available. This is perfectly reasonable, for a reproducer with a range extending to 10,000 cycles per second will reproduce up to the 20th harmonic of a 500-cycle note; while a reproducer having a range up to 3,000 cycles per second can only deal with the 6th harmonic of the same note. The chance of dissonance between two notes increases with increase in their harmonic content, owing to beats between harmonics. Use of the "top cut" control will therefore decrease the unpleasant effects of amplitude distortion, and it is to be expected that its use would be more effective when a combination of instruments is being reproduced because of small differences in the tuning of individual instruments producing beats between the higher harmonics. Let us consider the results of a recent series of tests in which a reproducer of the highest caliber was used to determine the frequency range which would produce the most pleasing reproduction. These tests were very extensive in that separate comparisons were made When asked what he thought of Law and Order, the sheriff of a Western frontier town of years ago replied that he guessed it was all right but he had never seen any. This is most apropos the unceasing discussions among engineers and laymen alike relative to the "proper" frequency range of sound reproducing means, whether it be a musical instrument, a radio, or a sound film reproducing system. Glib pronouncements anent "high fidelity" reproduction ranging from 30 to 10,000 and more cycles is just that: even if a reproducer were that good, it still wouldn't impress the general public, whose taste has been often correctly tabbed as strongly on the "low-frequency" side. Ten years ago a radio manufacturers' survey revealed that radio set owners invariably suppressed the high frequencies in favor of the "bassy" lows. Various aspects of this question are discussed in the accompanying article by a foremost British sound engineer who has done much original research on the topic. INTERNATIONAL PROJECTIONIST February 1947