Radio Broadcast (May 1928-Apr 1929)

THERE is no part of a broadcasting system, beginning with the studio and ending with the listener, which does not add its quota of distortion to the original performance which takes place in the broadcasting studio. Since the loud speaker is the last link in the chain of technical apparatus used in the system and the device which finally emits the reproduction of the original performance, it is natural, in fact almost traditional, to render judgment against the loud speaker for the accumulated deficiencies of the entire system, including the listener. While it is true that the loud speaker has been a gross offender in the past, and until recently the weakest link in the chain, there are many possible imperfections of the system which are in no way chargeable to this much maligned device. THE NATURE OF MUSIC AND SPEECH A LT HOUGH much has been written concerning the physical nature of speech and music, a brief review may not be out of place here, since it is fundamental to any study of loud speakers Sounds are more or less regular vibrations in material media. The most important of these media is air. The most important properties of sound are pitch, intensity, and timbre. The pitch of the sound is determined by the number of vibrations per second of the sounding body. When we speak of a musical note being high or low, we are speaking of the pitch of that note. The intensity of a sound we ordinarily refer to as the loudness of the sound. The quality of the sound is called the timbre. For example, the violin and the trumpet have different qualities or different timbres. All musical instruments emit certain vibrations which are called fundamentals. We can, for example, play middle C on the piano or violin, and the pitch of these tones will be, let us dAll cAbout jCoud Speakers i ■ ' / ' HIS article comes as a very timely comment J cm the present sweeping interest in loud speakers. The recent Trade Show at Chicago proved that the field of loud speaker development is at present the most active branch of radio. Mr. Morgan covers the whole field in a clear and concise manner, summing up the theoretical requirements of the ideal loud speaker, the various kinds of units that have been devised to meet these requirements and the results that may he expected from the present day types of loud speakers. Although the specific makes of units on the market to-day are not mentioned by name, the data in the text and the accompanying response curves should enable the reader to decide upon the type of loud speaker that will give him the kind of service he desires. In addition, Mr. Morgan gives some valuable hints cm the proper way to make a non-technical comparison of loud speakers. — The Editor. ^By Joseph Morgan therefore essential to reproduce all of the fundamentals and overtones in their original proportions. None may be omitted, none may be added, without causing distortion. Gross failure to observe these facts results in music which is unnatural and in which the various instruments are indistinguishable, and in speech which is unnatural and unintelligible. say, 256 vibrations per second. We are, however, enabled to distinguish the middle C's of the piano and the violin by what are called "overtones." These overtones are, in general, exact multiples of the fundamental pitch. For example, a certain instrument may have a fundamental (middle C in this instance) of 256 vibrations per second, with overtones of 512, 1024, 2048, and 4096; while in another instrument the overtones of 1024 and 4096 may be practically or entirely missing. Therefore, the middle C would sound quite different when played on the two instruments. In other words the overtones v/hich are present in a tone, and their relative intensities with respect to the fundamental, determine the timbre of that tone. The piano, for example, has 88 notes or fundamentals. Each fundamental is associated with its own group of overtones, and this particular grouping of tones gives the piano its characteristic quality. In the reproduction of speech and music it is function of the ideal loud speaker \ A /HAT constitutes the ideal loud speaker " from the point of view solely of tone quality? Assuming the broadcasting, the transmission of the radio waves through space, and the remainder of the receiving apparatus to be ideal, should the loud speaker reproduction be an exact replica of the original performance in the studio? The answer to this question is not so simple as one might, at first glance, suppose. In this apparently simple question there are involved physical, psychological, and physiological factors. It is not possible in this article to analyze the many factors involved, even aside from the fact that the relative importance of some of these factors is not yet known. A few illustrative points, however, may not be out of place. Amongst the important physical factors to be considered is the relationship which exists between the broadcast performance studio and the broadcast listener's room. The voice of a speaker delivering an address to an audience in a large auditorium will sound anything but natural if accurately reproduced in a very small living room. An orchestra, playing in a hall which has good acoustics, will sound most unnatural if accurately reproduced in a small resonant room; one, for example, with bare floors and walls, and containing very little furniture. It is very probable that a loud speaker could be constructed with certain intentional distortions which would give a better illusion of reality, in such a case, than a loud speaker causing no distortion. As to the psychological factors, there are people who actually prefer certain types of faulty reproduction to the original, and there can be no question that a poor loud speaker may under certain conditions flatter a poor performer.