From The Lab by George W. Tillett (Jan. 1974)

by George W. Tillett

Who invented quadraphonic sound? Dr. Murry of Chicago tells me that he had "what is now called quadraphonic sound" in his listening room in 1965 and the special corner speakers were the subject of a 1966 patent. [A subsequent patent shows 4 phono cartridges mounted on an arm-a most impracticable concept! ] But the concept is really much older; in fact, it goes back to 1931 at least. I am referring here to the well-known Blumlein patent (394350, 1931) which says " ... vertical displacement of the source will in this arrangement give phase differences to the outputs while lateral displacements give amplitude differences and these can be separated, the phase differences converted to intensity differences by modifying networks, as described and the resulting impulses employed to operate four or more loudspeakers .. . the transmission in such a system occupies only two channels up to a point in the system where each of these channels is divided into two parallel channels, thus providing four channels." The patent was described in a letter to the "Wireless World" (August, 1973) by a B.J. Shelley to whom I am indebted for the reminder.

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Most of our present day phono cartridges give best results with an amplifier input capacity of about 200 pf which is normally supplied by the screened leads. But what happens with CD-4 cartridges which must perform up to 50 kHz? The shunt capacity is obviously too high and so the leads have to be changed for low-capacity cables having a capacity of no more than 10 to 12 pf per foot at most. Now the problem is this: How to supply the extra capacitance when using a standard cartridge? Well, of course, CD-4 protagonists will say-keep the CD-4 cartridge for both stereo and 4-channel Quadradiscs--but try telling this to someone who has just invested $70 or so in a Shure M-15 Mk III or a Pickering 1200! At the moment, I am playing all my records-SQ, Quadradisc and stereo--with an Audio-technica 20SL cartridge which has a Shibata stylus and I find it to be very satisfactory although I have not had the chance to A-B it against my trusty ADC XLM or London Professional.

And now for two books, both of which I can highly recommend. The first is Modern Sound Reproduction by Harry F. Olson who needs no introduction (sorry for the cliché!). There are 328 pages plus index and no less than 250 illustrations covering binaural, stereo and quadraphonic reproducing systems, room design and acoustics. There are 17 chapters with sections on earphones, tape recorders, microphones, acoustical measurements, and loudspeakers. The last chapter is probably the most interesting as it deals with little-known data concerning the human hearing mechanism, subjective response to non-linear distortion and similar subjects. With such a wide range, it is inevitable that some subjects can be discussed only superficially but the author does recommend books for further study and it is remarkable just how much information is crammed into those 300 or so pages. The "blurb" on the ornate red and black cover describes Harry Olson as the retired staff Vice President of RCA Laboratories with 45 years service and the Library of Congress publication data reads: "Olson, Harry Ferdinand 1901. May we wait a good many years before the next date...." The publishers are Van Nostrand Reinhold and the price is $17.50. The second book is entitled The Liberation of Sound and the author is Herbert Rosscol. It is nothing to do with Germaine Greer or Bella Abzug, but it deals with electronic music and the various composers (if that is the right word). Varese is discussed at some length and there is a comprehensive chronology and bibliography as well as a list of recordings. The author's point of view can best be summed up by his remarks in the preface: "The argument of noise is always irrelevant.

The true question is, does this noise, when familiar, fall into intelligible forms and convey notable contents? To supply the answer takes time. One hearing, two, three hearings are not enough. Something must change in one's sensibility as a whole, in just the way that permits a foreign language suddenly to break into meaning and melody after months or years of its being mere noise. As a veteran of the premier of Stravinsky's Sacre du Printemps in Paris, I can testify to the reality of the transformation. At the end of the work, in 1913, the conductor, Pierre Monteux, turned around amid furious howls of the audience and said that since they liked the piece so much he would play it again. The response was no better, and the police had to be called in to quell the tumult. But now, sixty years after, the young accept those hammering rhythms and dissonant chords as if they were lullabies." The book is very readable-even if you don't like Varese, Stockhausen, Cage, Babbitt et al.... Publishers are Prentice Hall and the price is $10. (315 pp.).

Cassette Tests

A couple of notes to put with the cassette tape tests which appeared in the October issue.

Advent tells us that they no longer use the Advocate brand name and have changed to screw construction. Ampex cassettes are of welded construction, while Maxell UD and LN cassettes are screw assembled. TDK LN cassettes will be available only until dealer sup lies run out.

The statements on frequency response and headroom should not be compared between the chromium dioxide and ferric oxide portions of the tests, as some readers are reportedly doing.

They were meant for comparison only within their respective sections. As we have stated a number of times in the past, CrO2 tape is superior to FeO2 tape in frequency response and S/N. This margin appears to be decreasing with the recent developments in ferric oxide.

Several readers were concerned because response of some cassettes was not as high as specified by the makers.

For example, Maxell claims a 3 dB point of 15.7 kHz for the LN tape and 17 kHz for the UD. These tests place a great premium on the recorder, as we have often said, and a small change in set-up, bias (if adjustable), or test method can make a large difference in results. However, while absolute response of the tapes might vary, relative ranking would remain the same.

In the future, we will include tests of new brands and formulations as part of our tape recorder tests.

Audio Fallacy

Tape is a better medium than records. Wrong--at least in terms of absolute fidelity. Records made by the direct disc method (e.g. the Sheffield series) are superior to those made with a tape intermediary. The difference is mainly in transient response but it can definitely be heard in an A-B test.

(Audio magazine, Jan. 1974)

Also see:

From The Lab by George W. Tillett (Oct. 1973)

Automatic or Manual turntables--which one to buy? (Jun. 1973)

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