ACOUSTIC INSIGHT
The Master Handbook of Acoustics, Second Edition by F. Alton Everest. TAB Books, 366 pp., softcover, $18.95.
This second edition of Everest's successful Master Handbook of Acoustics provides very worthwhile updating. The useful new information includes sections on diffraction-grating diffusors and TDS measurements.
The first chapter of the handbook takes a brief look at the fundamentals of sound, discussing such things as harmonics, complex waves, octaves, and white and pink noise. The next chapter, on hearing, has broad cover age of subjects ranging from the anatomy of the ear through phons, sones, binaural localization, and the Haas effect to hearing loss from aging and environmental factors. The text is relatively brief but is lucid, aided by well chosen Figures.
The following five chapters are quite short, but each one covers a limited subject area. The result is more than adequate detail on levels and the decibel, sound waves and outdoor propagation, comb filter effects, sound in doors, and echoes in smaller rooms.
Important subjects include refraction, diffraction, and reflections. I thought the coverage on the causes and elimination of comb-filter effects and on room modes was particularly good.
In Chapter 8, Everest discusses the good and bad of reverberation and its relationship to understanding speech and enjoying music. He also covers test sources and equipment for measuring and displaying reverberation decay. The chapter even points out the effect of chart-recorder writing speed on measured decay slope. Optimum decay times, the use of artificial reverberation, and how to calculate decay time for a room are given brief attention. The next chapter, entitled "Common Signals-Noise, Speech, and Music," actually has little on noise, but the material on properties of speech, the vocal mechanism, musical instruments, and dynamic range requirements has satisfactory detail.
"Absorption of Sound" is important for the amateur acoustician. The author gives right-to-the-point rules on the use of various materials. For example, he correctly points out how studio owners cause problems when they use carpet for the main absorbent material. Al most half of the chapter is spent on the design and characteristics of low-frequency Helmholtz resonators. I won't fault Everest for some extra words on his experiments: They help the reader get a feel for the design process, and there is little practical information on designing and building resonators elsewhere.
The need for the diffusion of sound within spaces, how to evaluate diffusion, and the effect of room shapes and positioned absorbent material are covered briefly but quite lucidly in Chapter 11. The next chapter discusses the important work of Manfred R. Schroeder and the development of various diffusor panels. Information, including diffusion patterns, is included on specific models. A brief chapter on heating, ventilation, and air-conditioning systems for studios has worthwhile recommendations on ducting, plenums, and silencers.
The next four chapters cover the acoustics of home listening rooms, small recording studios, multi-track recording studios, and control rooms, respectively. The author delivers good, practical guidelines for all of these rooms. The chapter on listening rooms is particularly welcome: So many books on sound and acoustics have little or nothing to say about the place most of us usually experience music.
The chapter on control-room acoustics emphasizes LEDE (live-end dead-end) approaches, the initial time-delay gap, and use of diffusors. One Figure has a confusing caption, but my second thoughts clarified the point being made. The wide field of acoustical measurements, Chapter 18, is covered only in part, and most of the brief chapter is on TDS tests and the Techron TEF instruments.
The two-page appendix of absorption coefficients is short, but it's a good list. A 10-page glossary is nice to have but contains some errors. For example, C-weighting is not flat, as stated. A good inclusion is the list of 178 references, in the same order as the chapters, with entries as late as 1987. The six-page index covers the book's con tents well. The volume is highly read able both because of the author's style and the large, type size. Figures, in general, are very well done. All of the headings are the same size typeface, regardless of importance, and that's slightly confusing. The book is soft cover, but the pages are bound in stitched signatures. The book is not really a handbook in the strict sense because it does not cover all aspects of acoustics, and more details would be helpful in some chapters; The Master Handbook of Acoustics, however, provides a great deal of helpful insight in its selected areas for a very moderate price. Recommended to anyone who needs basic guidelines for good acoustics for home listening or a variety of professional needs.
-Howard A. Roberson
Electrostatic Loudspeaker Design and Construction by
Ronald Wagner. TAB Books, 248 pp., softcover, $14.95.
It is impossible to compare this to any other book dedicated to the de sign and construction of electrostatic loudspeakers because, as far as I know, there are none! For this reason alone it should be of interest to anyone who desires to know more about electrostatic loudspeakers, especially how to build one. I met Ron Wagner about 12 years ago, and at the time he was building full-range electrostatic speakers as a dedicated hobbyist. I haven't spoken to him about electrostatic loud speakers since then, but apparently his dedication has never waned. In the preface, he states his reason for writing the book: "The most obvious reason for writing a book on electrostatic speakers is that it hasn't been done before." His other intentions are to provide a text which can be used as a reference and as a guide for building an electrostatic loudspeaker.
The book can be divided into five areas. Nineteen pages of historical in formation are presented in Chapter 1; 39 pages of general information on radiation of sound, loudspeaker parameters, and measurements are in Chapters 2 and 3; 105 pages deal directly with electrostatic loudspeaker theory, construction, and testing in Chapters 4 through 13; eight pages on the Quad and Acoustat electrostatic loudspeakers are in Chapter 14, and three excel lent articles by other authors are re printed in the 52 pages of Chapter 15.
There is also a three-page appendix, which lists all of the parts needed to build the full-range electrostatic loud speaker described in Chapters 5 through 13, and a two-page index.
I found the historical background in Chapter 1 to be very interesting, since it gives not only the inventors and dates for specific inventions in sound recording and reproduction but also the patent numbers, so that those interested in pursuing the investigation further may do so. As in all first editions, there are errors which can be blamed on the "poor old typesetter." On page 13, while discussing Fig. 1.13, which shows the lens of the Beveridge speaker, the text describes the channels of the lens as being designed in such a way "that their effective sound paths were equal"; the word should be "unequal," and this is verified by the Figure itself, which shows that the out side lens channels are longer.
Since the author states, in the introduction, that "the book is intended for the audio amateur, musician, crafts man. . . ," I should advise anyone who might think this work lacks mathematics and physics that this is not the case. Chapters 2, 3, and 4 discuss the basic physics of electromagnetics and electrostatics and do require some familiarity with both, as well as a working knowledge of algebra. This should not scare off anyone who is really interested in knowing how electrostatic loud speakers work; a little brushing up using a very basic physics review-type book is all that may be necessary, and if you are interested in building an electrostatic loudspeaker only, you probably don't even need that.
Chapter 2 is, in a sense, misnamed. Although "Electromagnetic Speakers" does go into quite a bit of detail describing how they work, it deals mostly with information more appropriate to electrostatic loudspeakers, such as factors influencing sound radiation in general. An interesting aspect is the author's use of Bessel functions to re late the reactance and resistance versus the frequency of a loudspeaker's impedance and, later, the acoustic radiation versus angle and frequency.
There are more typos in this chapter, especially on page 35, in the section on "The ka factor," where "k" is given twice, with slightly different numbers.
There is also an assumption on this page that the cone radius of an 8-inch loudspeaker is 4 inches, which is not true. This is not only something that could be corrected in a future edition; it could be eliminated entirely, since this is a book dealing with electrostatic speakers and not electrodynamic cone types. Chapter 3 shows how to mea sure some speaker parameters and uses a Radio Shack 40-1021 8-inch electrodynamic loudspeaker as an example. This is interesting and informative, but I would have preferred that the author use an electrostatic loudspeaker to obtain the parameters since this might not be obvious to at least some of his intended readers.
Chapter 4, "Electrostatic Loudspeakers," discusses the fundamental parameters of electrostatic fields and both single-ended and push-pull electrostatic speakers. In the exposition on the force created by an electric field, there are some typos in the equations, such as when the force is changed from newtons to pounds; 2.28 and 0.58 pounds in the text become 2.25 and 0.562 pounds in the equations.
Without building the electrostatic loudspeaker, it is hard for me to completely evaluate the material presented in Chapters 5 through 11. However, they seem to contain a very detailed and orderly presentation of how to build the system. There are even checklists with block-shaped "bullets" to be checked off as you complete each task. (You might want to make copies of these, if you do decide to build the system, so that your book can be used again to build another.) Mechanical drawings, perspective drawings, and photographs aid in making the parts and building the complete system. Chapter 12 deals with the high-voltage power-supply electronics necessary for use with the electrostatic loudspeaker. A little more detail would be useful here, especially for amateurs who might not be familiar with electronics construction and, in particular, with high-voltage power supplies; even a photo or some line drawings would be a welcome addition. Chapter 13, "Speaker Evaluation," is only two pages, and perhaps could be expanded a little more in future editions.
Chapter 14, "Commercial Electrostatic Speakers," presents photos and schematics for the Quad Model 63 electrostatic loudspeaker, but only a living-room photo (and no details) for the Acoustat electrostatic loudspeaker.
Chapter 15 consists of three "Noteworthy Articles" by R.J. Matthys, P. J. Walker, and Charles I. Malme. These are very informative articles, and considering the cost of reprints of articles and papers, they're probably worth the cost of the book by themselves.
I do recommend this book to anyone interested in electrostatic loudspeaker theory, design, or construction. I also recommend that you obtain a book referred to by the author in his text; it is Electroacoustics, by Frederick V. Hunt, available from the Acoustical Society of America for $15.00 ( 500 Sunnyside Blvd., Woodbury, N.Y. 11797). Other sources of interest are Chapter 3 of the Loudspeaker and Headphone Hand book, edited by John Borwick and published by Butterworth and Co. ( Boston, Mass). Entitled "Electrostatic Loudspeakers," the chapter was writ ten by Peter Baxandall. I also recommend the various articles on electro static loudspeaker systems available in back issues of The Speaker Builder magazine ( P.O. Box 494, Peterborough, N.H. 03458).
-Edward M. Long
The Motown Album, Foreword by Berry Gordy, History
by Ben Fong-Torres, Essay by Elvis Mitchell, and Discography by Dave
Marsh. St. Martin's Press, 252 pp., hardcover, $50.
The release of The Motown Album was timed to help celebrate. Motown's 30th anniversary. Wrapped in a gold cover, the handsome book is primarily a photo album, and the best stuff dates from the salad days of the '60s when the Motown legend was being crafted hit by hit. The history that accompanies the photos is the work of Ben Fong-Torres. He has done a pretty basic job (there certainly is a potentially much larger book that can be done on the history alone), but for the purposes of this volume, it suffices. Dave Marsh's "Critical Discography," placed as a postscript, is more essential reading than the history. Here the songs are the topic rather than the personalities that dominate the bulk of the book.
And in the end, it is the songs that Motown is really about. Berry Gordy adds a foreword which is nice, if understandably a bit self-serving.
Let's face it. To shell out $50 for this photo album, you'd have to be quite the fanatic. I think the bucks are better spent on some sounds.
-Michael Tearson
(adapted from Audio magazine, Jan. 1991)
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