An Open Letter to Analog Cassette Hardware Manufacturers
The recording and consumer electronics industries have the opportunity to substantially improve the sound quality of prerecorded analog cassettes for the benefit of our mutual customer, the music consumer. As I will explain, the means for doing so is adjustable playback azimuth control.
The U.S. software market is divided roughly into three prerecorded media.
Analog cassettes control roughly 70% of the market, CDs 25%, and vinyl LPs 5%. The analog cassette is clearly the dominant medium in the U.S. It is important to note that the prerecorded cassette has outsold the blank in the U.S. for the last few years (in 1989 by more than 100 million units). Therefore, the fact is that prerecorded cassettes are likely to be used more often in cassette machines than cassettes recorded at home.
There has been serious effort by American music manufacturers to study and improve every part of the cassette duplicating process. As a result, during the last five years the recording industry has made great strides in improving the quality of prerecorded cassettes. Production improvements include the use of a digital source for running masters by virtually all manufacturers, improved mastering procedures, tapes, and recorders, and the constant testing of new duplicating formulations which are better able to meet the demands of digital masters.
Additionally, quality control systems have been tightened and retightened, and all incoming cassette components are given close inspection.
In short, there has been a systematic program by the recording industry to study every part of the cassette duplicating process and improve it. Moreover, Dolby S-type signal processing is on the horizon, and we are on the verge of moving away from analog and toward digital reproducers.
It is my opinion that there is now very little left that can be done unilaterally to improve cassette quality.
The fact is that all of the improvements made to date still represent only half the equation; optimum sound quality can only be achieved by having the cassette and the player perfectly matched in terms of playback azimuth and frequency response.
While today's music manufacturers can and do control the quality of their software, cooperation with the hardware manufacturers to "match up" both software and hardware is essential for that last "quantum leap" in sound quality. I believe that, with proper hardware and software compatibility, the sound quality of the analog cassette would be very close to that of the Compact Disc.
While a tighter fixed azimuth standard might in the short term provide improved sound quality, extended time and use invariably will cause changes in alignment. As a result, I believe that adjustable azimuth is the only way to assure continued proper alignment for both prerecorded and home-recorded cassettes.
The CD and the CD player work as a music system, with the machine adjusting to the software. Why not the analog cassette? Why not make the music as good as it can be? Why not work together in improving the format favored by our customers, the analog cassette?
-Edwin Outwater Vice President, Quality Assurance Warner Bros. Records Burbank, Cal.
An Open Reply to "An Open Letter ..." From a Hardware Manufacturer I wish to acknowledge the five areas of improvement listed in the "Open Letter" and add two that went unmentioned: The use of the Dolby HX-Professional Headroom Extension System and Dolby B noise reduction. Unfortunately, both of these improvements are not available in every prerecorded tape, but the trend definitely seems to be in this direction. Further, by the time this is in print, the first cassette decks with Dolby S noise reduction will be in production. It will be interesting to see how the software manufacturers and retailers react to this new 'system. Will both Dolby B and Dolby S encoded software be offered? Will Dolby B software be phased out? I also wish to voice my agreement that the best attainable sound quality can only be achieved when the software and hardware are matched in terms of azimuth and playback frequency response. However, my agreement ends where Mr. Outwater focuses on adjustable azimuth and goes no further on the subject of playback frequency response. I place the opposite priority on these two items.
To my knowledge, there is no technological excuse for poor azimuth alignment, only one of cost. It is our experience that quality components (specifically, the transport mechanism and the head assembly), a finely threaded azimuth setscrew, and a well-placed drop of adhesive will hold an accurate azimuth alignment for the life of the tape head. I know of no professionally obtained evidence to the contrary. I can confidently state that most of the worn heads replaced by our repair technicians are found to have accurate azimuth alignment. For this reason, I believe that a tight fixed azimuth standard will significantly improve sound quality and that consumer-adjustable azimuth is unnecessary.
In addition to being unnecessary, consumer-adjustable azimuth has serious drawbacks. Consider the following. The tape heads in all cassette decks unfortunately twist or jitter somewhat while in use. The effect of this twisting or jittering is that the azimuth is constantly shifting back and forth, developing a positive and negative error.
Even though the nominal, or average, azimuth can be adjusted precisely, the instantaneous error cannot. As can be expected, the best-sounding decks have fewer instantaneous errors. One way to minimize these errors is to positively secure the tape head. Any added mechanism or linkage to facilitate easy azimuth adjustment would inherently make the tape head less secure and increase these errors.
Also, hardware can most likely be designed so that, in the playback mode, the user can adjust the azimuth either by ear or with the aid of a test tape and some form of instrumentation.
But how does one adjust it when recording on a blank tape? Should the customer be expected to adjust his deck to an alignment tape prior to recording? How many customers will appreciate the added complication, and how many customers will adjust their decks correctly? And what if they adjust it incorrectly? The resulting tape will not sound good when played on other decks.
For these reasons, I believe that consumer-adjustable azimuth is counterproductive to the effort to obtain better sound quality.
The playback frequency response of many cassette decks in not as uniform as one might think. This is because the hardware industry highlights record/playback frequency response rather than playback frequency response.
In short, playback frequency response is that which is obtained when playing back a standardized test tape Record/playback frequency response, on the other hand, is obtained by recording test signals on a blank tape and playing the tape back on the same deck on which it was recorded. A deck with wide, flat record/playback frequency response can have compensating errors in its record and playback sections and poor playback frequency response. Such a deck will produce poor sound quality when playing back prerecorded tapes and would record tapes that would have poor sound quality when played on other decks.
What caused the situation we are in today? I believe that both the hardware and software industries are to blame.
Since there is always a large market for cheaper hardware and since the hardware industry doesn't highlight playback frequency response, poor-performing decks will command a share of the market. And while it is good to know that cassette software has improved dramatically in the last five years, what about the formative 10 years before then, when hardware manufacturers and consumers developed their sense of how good prerecorded cassettes tend to be? Accepting that software is less of a problem today, what will spur hardware manufacturers to tighten their standards? There are no government or industry regulations that force compliance to standards for azimuth and playback frequency response. Today, both government and industry are so fixated on digital recorders that analog issues are very likely to remain a low priority.
A possible solution may be indirectly offered by Dolby Labs. They are well aware of how azimuth and playback frequency response affect sound quality, and have specified tight tolerances in the Dolby S licensing agreement.
While this will apply only to higher priced decks at first, Dolby S will eventually become more affordable and, hopefully, will become a common feature. If that happens, the problems of azimuth and playback frequency response may both be solved, and the analog cassette will provide its full potential sound quality.
Marty Zanfino Vice President Engineering and Technical Service Harman Kardon Woodbury, N.Y.
(adapted from Audio magazine, Nov. 1990)
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