by LEONARD FELDMAN
Some of us have owned Compact Disc players for nearly two years now. Others have only recently taken the plunge, while many more readers of Audio are, no doubt, still holding out for a variety of reasons. My own reactions (almost entirely positive) to laser-optical digital audio discs were formed early on in the brief period that players and discs have been on the market. Those opinions haven't changed much since I purchased the first CD player I could get my hands on (the one I still own, incidentally). But it has occurred to me that my opinions might be colored by my access to some of the best CDs around, as well as by my opportunity to obtain some discs for nothing or next-to-nothing, as a reviewer and tester of equipment and as a member of the audio press. I wondered what the serious audio enthusiast was thinking about CDs and CD players-now that both have been available to us for some while.
Lacking the financial resources to conduct an official, meaningful poll, I saw no easy way to get a sample of opinion from audiophiles across the country. Then, a fortunate thing happened. I was asked to deliver a talk in some 22 cities around the U.S. as part of a seminar about digital audio and other advances in audio and audio-related video technology. After working out an itinerary that called for visits to three or four cities per trip over a period of three months, I agreed. And as a result I was able to communicate on a one-to-one basis with hundreds upon hundreds of interested audio enthusiasts, many of them with questions about CDs they had been unable to get answered satisfactorily. Many, too, had been fed misinformation by a variety of sources, ranging from uninformed sales personnel intent on selling the new CD technology even if they had to stretch the truth a bit, to quotes from advertisements created by over enthusiastic ad agencies who obviously hadn't checked back with their clients' technical people.
Because I came away from this period with a clear impression of what people want to know about CDs, I thought it might be a good idea to share some of the questions raised during this ex tended tour around the U.S. Some of the answers I gave are simply factual, while others, clearly, are my own opinion, formed after two years of familiarity with a variety of CD players and a good sampling of CDs. My purpose here is to help others make up their minds about the Compact Disc sys tem-whether to purchase a player now, later, or even perhaps never. I'll present the material as a question-and-answer session--much as I did during the actual seminars.
Q. When will the price of Compact Discs come down-and by how much?
A. Don't expect CDs to ever cost as little as mass-produced LPs. At present, manufacturing costs run about five times those of an LP. Remember, though, that CDs can contain more than an hour of music, as opposed to 30 to 45 minutes on an LP. Further more, high-quality audiophile LPs sell for prices comparable with CDs and always have-and, of course, CDs sound a lot better and last a lot longer than even the finest audiophile LPs.
Q. I've heard that CDs are indestructible. Is it true that you can scratch them or allow dust to land on them and that the laser will still read through these defects?
A. The ability of the laser pickup in a CD player to read around minor defects in a disc is truly remarkable, a result of the laser beam's focusing beneath the transparent surface of the disc. Sophisticated error-correction circuitry-an inherent part of the CD standard-also help. Because of this circuitry, the laser beam, in effect, has more than one chance to read the digital information if a dropout is encountered owing to an opaque scratch or dirt spot on the disc.
It should be emphasized, however, that these factors only work up to a point. If scratches are severe, or if dirt and dust are allowed to accumulate on the disc surface, any CD player will mistrack. The result will either be a momentary muting of the music or skipping pars of the music, or even repeating the same phrase of music over and over again. The same care should therefore be taken in handling CDs as you would take in handling your best LPs.
Q. When will the price of CD players come down to $200 or even $100?
A. Prices for CD players have already fallen dramatically, as manufacturers introduce more economically fabricated second- and third-generation machines and as LSI chips are designed to take the place of more and more discrete circuitry. But you must be careful when you shop. Ultra-low prices for CD players may also result from skimping in such important qualities as error-correction capabilities and laser-tracking stability, not to mention omission of convenience features found in the more expensive players.
Q. So, what are the major differences between CD players? Does one model sound different from another?
A. There seem to be some subtle sonic differences between different players, but these are relatively minor. Major differences involve programmability, the time it takes to access a given track, tracking stability, and ability to overlook minor defects in the disc through elaborate use of an individual unit's error-correction circuitry and techniques built into the CD standard.
Resistance to mistracking caused by external shock or vibration is another favor that varies from one player to another.
Q. Some CDs have come out that were made using analog master tapes.
Isn't that something of a rip-off? Shouldn't CDs be digital all the way from master tape to finished product?
A. Many fine-sounding CDs are being made from analog masters, and, frankly, there's nothing wrong with this practice if the original performance was worth preserving and the master tape technically well recorded. A good analog master tape can have more dynamic range than can be contained in an LP, so CDs made from such tapes do sound better and have more dynamic range than the LPs made from the same masters.
Q. Will we ever be able to record onto CDs, as well as using them just for playback?
A. I'm always puzzled by this question. Why should we expect to be able to record CDs at home when no one ever asks about being able to record LPs at home? At present, PCM processors enable anyone to make digital audio recordings using a videocassette recorder. Many large firms, including 3M, Sony, Philips, Sansui and Sanyo, are investigating this, however.
Q. With all that extra dynamic range in CDs, how much extra power will I need in my amplifier to take full advantage of CDs?
A. There's no one answer for this question. It depends upon how much amplifier power you now have, how efficient your speakers are, and at what loudness levels you like to listen to music. In general, though, some what higher amplifier power or a trade-up to more efficient loudspeakers, or both, is usually in order.
Speaking of dynamic range, it's worth noting that when CDs are played in cars, their dynamic range will be too great for on-the-road enjoyment. Ambient noise in automobiles is so high (often as high as 70 dB SPL, even with the windows closed) that, in order to hear the softest passages of music, the volume will have to be turned up so high that the loudest passages will either overload the typical car stereo system or be deafeningly loud. Many manufacturers of car CD players are expected to offer-either built into the CD unit or as an optional add-on electronic compressors to reduce these dynamics to a manageable range. Philips has already showed such a player in Europe. Of course, the CDs will continue to deliver their full dynamic range when played at home or with the players' compressor circuits turned off.
Q. I've heard rumors that we're going to see combination disc players that will play both laser videodiscs and CDs. When will such players be available?
A. The rumors have finally borne fruit-the first quarter of 1985 should see such players brought to market by Pioneer (and by Sony and Technics, selling units actually made by Pioneer).
Pioneer's dual-purpose machine, how ever, is not only more expensive than a CD player alone, it's a good deal more expensive than a CD player and a LaserDisc player together, though the combination unit takes up less space than the two single units it replaces.
Q. Isn't it possible to produce CDs with music on both sides? If so, why aren't record companies making two sided CDs?
A. Yes, it is possible and provisions for such discs were made when the standards were set. Still, you're not likely to see two-hour, two-sided discs in the foreseeable future, for two reasons. First, although the yield of discs now exceeds 80% (eight out of 10 CDs that come off the molding machines pass quality-control tests), sandwiching two discs together, back to back, would automatically double the quality-control problems, dropping the yield rate to around 60%. Second, a double-sided disc would have no space for a label, and it might not be compatible with existing players and pressing equipment. Then, too, in the case of popular-music recordings, the extra royalties for the additional selection needed to fill two sides of a CD would raise the cost of such discs prohibitively, thus reducing sales.
Q. Why isn't there at least the hour of playing time that can be put on a single-sided CD? Most CDs seem to have no more music on them than regular albums.
A. Consumers have a valid complaint here. Unfortunately, most record makers simply transfer the programs used for making LPs (whether from digital or analog master tapes) onto CDs. A few (especially in the classical field) have seen fit to append a short selection after the main musical program, such as an overture to a disc containing a symphony or two by the same com poser. In the popular-music field, record companies would run into the same problem of additional royalties for added songs that they would if they made double-sided discs. But if you want more music on your CDs, you should make your voice heard at the record companies, by requesting that those companies fill out their CDs to full length more often.
Q. There is a vast amount of unused storage space in CDs. What can this extra data storage space be used for, and when are we likely to see CDs that include such additional data?
A. There are several areas of unused storage space in CDs as they're currently made. So called "subcodes" bearing the identifying code letters R through W are available for a variety of data storage. Among the kinds of data being considered are digitally generated graphics, not unlike those available on home computers and teletext. A CD has enough data storage space left, after including stereo audio and track/ time display information, to generate approximately 250 still-pictures during the course of an hour's worth of re corded music. Such pictures, displayed on a TV screen with an add-on "black box" connected to the CD player, might show the lyrics of a song, the libretto of an opera, or scenes appropriate to the music-in fact, almost anything you can imagine.
Q. Some CD players apparently use a higher digital sampling rate-does this result in better sound? What's the story on this?
A. Another source of confusion. There's only one sampling rate for the CD system: 44.1 kHz. For that matter, there's only one "bit" count for CDs too: It's a 16-bit standard. Talk of 88- or 176-kHz sampling rates has to do with the way in which various CD players decode or read the information contained in the disc. Some, for example, read the same sample two or four times, in a technique called oversampling. Others use a 14-bit D/A (digital-to-analog) converter but end up achieving the full dynamic range and other characteristics inherent in the 16-bit system. Each approach claims sonic superiority, and you are invited to judge that for yourself. But the basic world standard set for CDs employs one, uniform sampling rate and a 16-bit sampling system.
While these dozen questions may not answer everything you want to know about Compact Discs and CD players, the important thing to remember is that CD technology is scarcely two years old. By contrast, we've been dealing with analog audio recording in one form or another for more than 108 years. It will take a little more time till we have all the answers for a technology this new. I, for one, am willing to wait while I enjoy the better sounds I'm getting-even with my first-generation CD player.
(Audio magazine, Apr. 1986)
Also see:
A Compact Introduction to the Compact Disc (Apr. 1986. CD)
Sony D-5 and Technics SL-XP7 Portable Compact Disc Players / Battle Of The Portables (Apr. 1986. CD)
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