SIGNALS & NOISE (Letters to Editor) (Jul. 1989)

Gotcha!

Dear Editor:

I was a little surprised to read Irene Lirpa's advertisement--er, letter--in the April issue. How convenient that you should print her "information" in the "Signals & Noise" column. Had you used a little better judgment in letting readers know what's available out there, you could have cited Lirpa World Tours' service as something you discovered and included it in "What's New." Better yet, you could have let Ms. Lirpa take out a quarter-page ad in your magazine.

No, I am not involved in any business like Irene Lirpa's, but I am a reader of Audio who objects to its recent lack of judgment.

-Gerry Bokas, Jr.; Royal Oak, Mich.

Editor's Note: Ms. I. Lirpa's name, backwards, is ....-E.P.

The Unnamed Voice Takes the Mike

Dear Editor:

I was the unnamed public radio engineer quoted by Edward Tatnall Canby in his August 1988 column, and I would like to respond to Stanley Lipshitz's interesting January 1989 letter commenting on the column.

I had not heard of the curious phenomenon elucidated by Mr. Lipshitz in which level differences between left and right loudspeakers translate into timing differences between the ears.

Fascinatingly counter-intuitive! It is not without trepidation that I venture to contradict the redoubtable Mr. Lipshitz. Nevertheless, I cannot agree with his conclusion that a Blumlein recording (one made with a pair of coincident figure-eight mikes crossed at 90°) will give results in every way superior to an arrangement of spaced microphones. Blumlein certainly does provide superb lateral imaging, but not depth--at least to my ears. At NPR workshops at SUNY, Fredonia and the University of Iowa, I participated in experiments in which the same performance was recorded on multi-track tape using several pairs of mikes, so that different microphone techniques could be compared directly. I was present while many of the recordings were made, and so was able to hear what the performance actually sounded like in the hall. In no case did I find that any coincident technique gave the most lifelike reproduction. In all fairness, not everyone agreed with me, but neither was I completely alone in my perception. I do not agree that this is entirely a matter of the reverberant characteristics of the recording. In most cases I found a closely spaced array, such as ORTF (cardioids spaced at 17 cm and angled at 110°) to give the most realistic and pleasing results, combining a fair degree of lateral imaging accuracy with a sense of openness and depth simply not there with the Blumlein (or other coincident) pickup.

What I know about mike techniques I have learned on my own. I came to the field of classical music recording essentially without prejudices (being too ignorant to have any), and enthusiastically tried the first "stereo-mike" I came across, the highly respected AKG C24. But I was disappointed with the result then, and have been ever since.

As Mr. Lipshitz points out, stereo is a flawed medium not entirely capable of bringing the listener into the concert hall. Since complete accuracy is impossible, I suggest that there is room for valid disagreement about which compromises work best.

-Steve Graham, University of Michigan, Public Radio Stations, Ann Arbor, Mich.

Mr. Lipshitz Replies:

Mr. Graham is not alone in being unaware of the level/ time interchange between loudspeakers and listener's ears in stereo reproduction. This is why I wrote a detailed paper which examines the whole stereo question and substantiates my claims ("Stereo Microphone Techniques--Are the Purists Wrong?" Journal of the Audio Engineering Society, Vol. 34, No. 9, September 1986). Some of your readers may be interested in examining this paper or even in ordering the demonstration cassette produced to illustrate my points. (It is available for $10 in Dolby B or C NR from the Audio Engineering Society, 60 East 42nd St., New York, N.Y. 10165.) Good Blumlein stereo requires microphones with excellent figure-eight I patterns. Large double-diaphragm mikes like the AKG C-24 may not be good enough in this respect; I would suggest a reduced angling between 80° and 85°. The Schoeps MK-8 figure eight capsules are excellent and should be used at 90°. I find "phasiness" on the direct sound objectionable, and there is no way of avoiding it with spaced microphones. I cannot agree that good Blumlein stereo is lacking in "depth," but no stereo technique can provide "lifelike" reproduction, in my view.

The audible differences between coincident and spaced microphone techniques are largely not a matter of how these techniques handle the reverberant sound (Blumlein can be very similar to spaced omnis in this respect) but rather of how they handle the direct sound. Many people mistake phasiness on the direct sound for ambience.

Yes, indeed, there is room for valid disagreement, since there is no accounting for personal preferences. Try my tape and see what you think.

-Stanley P. Lipshitz; Audio Research Group, University of Waterloo Waterloo, Ont., Canada

Watching the "Roadsigns"

Dear Editor:

As an engineer and constant reader of the "Roadsigns" column, I took particular interest in "Take a Balanced View," which appeared in March. In that item, Ivan Berger describes the real benefits of fully balanced (or differential) output/input signal connections for automotive audio systems. He then references an article by John R. Bishop ("An Informal History of Car Amps," May 1988) that states that while some companies do use differential inputs, "they all hook those inputs to unbalanced lines." I'm writing this note to tell you that at least one company does not commit this transgression: Ford Motor Company. Since the 1988 model year, all Ford audio systems with the Electronic Premium Cassette (EPC) radio are fully balanced systems, consisting of balanced drivers in the radio and balanced input circuitry in the amplifier.

This includes both Premium Sound and Audiophile sound systems. The action was undertaken for the exact reason mentioned in your article: Improved common-mode rejection.

Keep up the good work. I'm looking forward to my next issue.

-Henry Blind; Product Design Engineer, Audio Systems & Applications Ford Motor Co., Dearborn, Mich.

Old but Not Outmoded

Dear Editor:

It is only in the past couple of years that I have been able to devote some resources to my favorite hobby-those resources being money and that hobby being, of course, sound systems.

As a newcomer, I have found, much to my pleasure, that there is a lot to learn.

Along with my limited experience comes the welcome advantage of an objective view. But the more people I meet in the audio world, the harder it seems to be to get an objective opinion. This, of course, forces me to form my own. It is one of these opinions I would like to share with you, the topic being the turntable.

When I junked the system I listened to in college and began rebuilding, one of the major decisions was whether to incorporate a CD player, turntable, or both. Obviously, if you choose only one, it's easier to build the system.

Although I was no world-record album collector, I had amassed a number of LPs. But the question still remained. I upgraded my system, purchasing everything except a new turntable, and began buying CDs. Reading the local swap paper one day, I noticed a Linn LP12 for sale. Yes, the infamous Linn.

One of the reasons I had not purchased a turntable up to that point was the fact that the price of a good reference table was quite high. Well, I couldn't refuse the Linn's price, so I went out and purchased it. After a little scouring, I even came up with a Syrinx PU2 arm that, by chance, was the one for which the arm board on the Linn was originally drilled.

To make a long story short, my Linn is quite a rival to my CD player. I'm back to buying LPs. And with a reference table like the Linn, its infinite adjustments allow me to tailor the sound to my ear; I'm not forced to listen to what I'm told music should sound like.

Thank God for the CD. It has put affordable reference turntables on the used market. In the future, please don't forget new diehard turntable people.

-Joe Vastola; Buffalo, N.Y.

Calling All Call Letters

Dear Editor:

In the April 1989 "Audio ETC" column, Edward Tantall Canby incorrectly identified the key station of NBC as WABC. It was actually WEAF, which became WNBC at the time NBC was forced to divest itself of its Blue Network. The network then became known as the Blue Network of the American Broadcasting Company and, later, ABC. Its key station was WJZ, which became WABC nearly a decade after ABC's inception. WNBC became WRCA from 1954 to 1960, at which time the call letters reverted back to WNBC, which they remained until a few months ago, when the station ceased operation. The WABC designation to which Mr. Canby refers belonged to the station that became--and remains today--WCBS. Scrabble, anyone?

- Eli Segal; Richton Park, Ill.

(adapted from Audio magazine, Jul. 1989)

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