Behind The Scenes (Apr. 1972)

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by Bert Whyte

As I AM SURE you have noted, in this issue of AUDIO, the emphasis is on open reel magnetic recording. Thus it is an appropriate time to ask how fares this granddaddy of all magnetic tape formats? In spite of all the doomsayers and carping critics who have been trying to bury open reel for the past few years, this medium is alive and well and is in fact flourishing. Does this run contrary to what you have been told? The key is in recognizing the distinction between the market for open reel tape recorders and that for open reel pre-recorded tapes. Almost without exception, the manufacturers of open reel tape machines have been enjoying excellent sales and growth. This is particularly true with tape decks in the higher priced category--from $300.00 upwards. It would appear that the market for low end open reel decks is virtually dead, with the better quality cassette decks filling this void. Nonetheless, even with the low end decks out of the picture, the dollar volume of open reel machines has been rising.

The sales of open reel tapes has been slowly declining over the past few years, but not for the reasons usually cited, such as handling problems and high cost. I'll go into that a bit later.

There has been a tendency on the part of some people to lump the open reel decks and open reel tapes together as a single market entity, thus giving rise to the stories of the imminent demise of this format.

As even a casual look at the open reel tape deck market will show, there is plenty of activity. Hardly a month goes by without the announcement of a new model tape deck or of related accessories. Nor is this activity confined to the old line established open reel manufacturers. Look who is in this market now ... Sansui, Kenwood, Pioneer, Panasonic-all big receiver manufacturers and all with one or more models of open reel tape decks.

In truth, the entire open reel market is in a state of flux (pun intended). Everywhere you look there is revision, refinement, innovation, evolution.

Revox has new models with built-in Dolby B type noise reduction circuitry.

Teac has their own accessory Dolby B boxes to go with their new SL tape decks. Akai and Tandberg have updated their crossfield head models. Easy accessibility and adjustment of bias for the burgeoning array of low noise tapes is becoming commonplace.

Ferrite and ferrite/glass heads are being used on a number of new decks.

And as for four-channel open reel decks, the variety of models is quite astonishing. Sony has come up with a four-channel record/play model for $299.95. Wollensak has a deck with two-channel record/play and four-channel playback. Crown has the same arrangement in one of their models and uses up to 10 1/2 in. reels. In spite of the disastrous fire at the Crown factory last Thanksgiving Day, they will soon be back in production on their big "built like a battleship," 10 1/2 in. four-channel record/play decks. Kenwood has a four-channel record/play deck with a very handy front/rear headphone switch. If you do any live four-channel stereo recording, you will find that monitoring is a sticky problem and this headphone switch is in real help. Astrocom will soon be producing their Model 711, a 10 1/2 in. four-channel stereo record/playback deck with individual synchronous recording facilities on all channels. By the time the Consumer Electronics Show in Chicago rolls around, sometime in June, there will be very few open reel tape deck manufacturers without a four-channel stereo deck in their line.

Those critics who look with jaundiced eye at the discrete four-channel open reel format are vociferous in their objections to the continuing proliferation of four-channel decks when there are so few prerecorded four-channel tapes to play on these decks.

You know, these characters have always been around since the beginning of the hi-fi era, and they never change.

When stereo arrived about 1954 (via tape of course) they were moaning about the dearth of tapes, that stereo was a "rich man's game," that they were going to "stick to monophonic," etc., ad nauseam. They give me a pain.

What the hell did they expect ... that a comprehensive catalog of stereo tapes was just going to "spring into being"? Fortunately, a recent development will still the voices of these fulminating critics or at least bring them down to sotto voce. I told you last month about the impending release of four-channel open reel tapes from Project Three and Vanguard Records, and I am happy to confirm this. I recently spent a pleasant afternoon with Enoch Light, discussing the entire four-channel stereo situation. Mr. Light told me he had done very well with four-channel stereo tapes in 1971 and was thus encouraged to issue nine new open reel tapes. Incidentally, the same material will be released on discrete four-channel stereo cartridges and on Sansui and EV matrix discs. Mr. Light intimated that henceforth four-channel open reel tapes would be issued on a regular basis. Mr. Light's Project Three catalog of four-channel open reel tapes now lists 18 productions. Vanguard will release new open reel four-channel tapes including pop material by Joan Baez and others and for the classical enthusiast such items as Handel's "Messiah" and oratorio, "Judas Maccabeaus." Then there is the Tchaikovsky 4th Symphony with Leopold Stokowski conducting his American Symphony Orchestra, the Cherubini "Requiem Mass," and several other works as yet unknown to me. To top it all, these new Vanguard four-channel stereo tapes will be issued with Dolby "B" type noise reduction in front and rear channels! This presents an opportunity for someone like Advent or Teac to come up with an inexpensive playback only Dolby "B" box for the rear channels.

The anticipated introduction of the Signetics Dolby "B" IC chip should make such a unit a reality before long.

I should also mention a discrete four-channel open reel tape issued by Dick Shory's Ovation Records. Actually it is a two reel release of mostly pop "surround" music. It is very well done, with intelligent use of the four-channel medium and it has been processed with care for an overall excellent sound quality. Presumably Mr. Shory will be issuing new material, in view of the Project Three/Vanguard releases. Now, with close to 40 four-channel open reel tapes available, the purchase of a four-channel open reel tape deck will be more attractive and practical.

As I mentioned earlier, most people seem to think that the reason for declining sales of open reel tapes is the handling/threading problem and the higher costs of the tapes. While admitting the threading is a problem for some people, let me say, with malice aforethought, that if you gave these people the tape for free, you would be surprised how fast they would learn to thread tape! OK, so obviously no one is going to give tapes away, but in the larger cities where tape is discounted with the same fine fervor as discs, the same piece of music on tape or disc has almost reached price parity.

What really has been the trouble with open reel tape sales is sheer availability of the tapes in the record stores and department stores throughout the country. As I pointed out last month, Ampex decided to try and remedy this with a mail order service and the response was so astonishing that the project was immediately elevated from an experiment to a permanent service. The other reason that open reel sales were declining was that no one had done anything about the tape hiss that was the only flaw in otherwise fine recordings. I covered this last month too, and I don't want to beat a dead horse, but if repeating can help make it happen, I'll babble on all day ... process open reel tapes with "B" Dolby and open reel sales will be the success story of the year. 'Nuff said.

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All right, so the open reel tape deck market is in a healthy state. And you want to keep your open reel deck in a healthy state too! In previous issues I have gone over the importance of demagnetization, the inadequacies of most consumer type degaussers, and the special qualities of the R. B. Annis Handimag unit. I duly mentioned the importance of frequent cleaning of the heads and tape path. Well friends, I had an experience recently that calls for another look at the cleaning process.

I was making some tape dubs for a friend, playing back a 15 ips two-track Dolby A type master and feeding the output of the Dolby 361 units into a Dolby B box and thence into the dubbing recorder. After setting the correct Dolby B playback levels on the meters of the B box, I was feeding the Dolby tone into the recorder to set the record levels on the blank tape I was going to use to make the dub. Usually, it takes two or three passes, with various adjustments of the recorder's input gain controls to establish the proper record level. But this time I was having problems. If the meter indicated I had to come down slightly to achieve the desired level, once the control was adjusted, the result was not as anticipated.

If I had to come up in level, the control adjustment was off here too, in fact more so than when I wanted to attenuate. Suspecting it might be dirt on the heads I applied Q Tip and alcohol and there was slight brown/black coloring on the cotton, but certainly nothing that would have caused the noted fluctuations. Tried to set levels once more .. Same result. Tried again, and this time the left channel was way down (later measurement showed it to be off by 18 dB). I thought that it must be trouble with the record amplifier. Since the home service base of the manufacturer of the recorder was just a few minutes drive from my home, I took the recorder there. Sure enough their tests showed the 18 dB drop. But imagine my chagrin when the technician said that it was just a dirty head! I protested that not only do I clean the deck's heads about every 3rd or 4th recording, but that I had just cleaned the heads before I came to him. The technician picked up what looked like a miniature tooth brush, except that instead of bristles, there was a square of fairly stiff white felt cemented to it. He moistened it with alcohol and really scrubbed the heads. The design of the "toothbrush" allows you to exert considerable pressure. Needless to say, the once white tip was almost dead black. The deck was then swept from 20 to 20kHz on a Bruel and Kjaer frequency spectrum analyzer with graphic readout. The chart was just as pretty as could be.

I was still shook up that head dirt had really been the cause of the trouble.

Nevertheless, I armed myself with a supply of the fancy "toothbrush" cleaners, and it was a good thing I did for later I ran into the same trouble.

Now, depending on the brand of recording tape, some shed oxide more than others. But in general the top name brands of tape are rarely problematic.

The tape I was using was a top brand of premier low-noise formulation I had used with complete satisfaction many times before. But things do happen ... I found out that this particular batch of tape was exhibiting a phenomenon known as "pearling." Evidently under certain circumstances, some of the volatile agents in the binder, plasticizer, and adhesive are not driven off in the curing process, so the oxide surface remains ever so slightly "tacky," but enough that when the tape passes over a head, guide or roller, the friction created rolls off tiny little balls or "pearls" of oxide and adhesive. Naturally tape passing over this obstruction is lifted from the head with resultant drop in signal. The tenacity of this oxide "gunk" is incredible. Obviously the usual Q-Tip measures are ineffective and the added pressure and compactness of the felt is needed to dislodge the gunk. Usually when you buy a carton of ten or a dozen rolls of tape, they are all of the same "emulsion" number. If you have trouble with one of the tapes, you will almost certainly have it with the other tapes in the carton. Your only recourse is with the manufacturer, and in the meanwhile try another batch of tape. Thus it was with me ... using tape of another manufacture I did not encounter any troubles. In the light of my experience, I'm going to clean my heads more thoroughly in the future and keep an eye peeled for any tapes which seem to shed more oxide than usual. As a final note . .. I'm trying to find out the name of the manufacturer of the fancy "toothbrush" cleaner so they can be bought separately and in bulk. At present they come as part of a cleaning kit.



Professor I. Lirpa, of Bucharest, inventor of the Transpet, has sent us details of his quadraphonic matrix. The article may have suffered somewhat in translation as our Romanian is nothing to boast about-but here it is.

"Four-channel sound is not cheap as more amplifiers are required and then there is the decoder itself which uses expensive ICs. Also, these ICs can cause some phase-distortion. My idea (patents pending, RPO) uses just two loudspeakers mounted back to back (see Fig. 1) in the enclosure with a divider between. This divider, with two sections mounted at right-angles in front of the speaker cones, forms an acoustical matrix. It is made from wickerwork and the twig spacings are most critical.

Two small results in poor location and too large causes reduced separation.

The formula is: S = [A+N / A-10] V

Where S is the spacing in cm.

A is the cone area in cm^2,

N is the capacity of the box in liters.


V is the velocity of sound in meters/ sec.

Density of the material should be between 0.5 and 0.6 and the Cthula (Young's?) modulus not less than 1.3.

The resulting algebraic coefficients at 25 degrees C. are:


Rf = 0.561a-0.131b + 1.81c-0.671d

Lr = 1.31a + 0.1b + 0.54c-d

Rr =-1.3a + 0.97b-0.67c + 0.817d

The material for lab tests came from a Chinese basket used for another research project. The speaker system should be placed as near to the center of the room as possible and it could be used as a coffee table."

Fig. 1--Diagram of Lirpa quadraphonic speaker.

(Audio magazine, Apr. 1972; Bert Whyte)

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