21 Audio Myths
Mythbusting Stereo Review- style. We look back at Peter Mitchell’s 1983 feature tackling topics ranging from weighted specs to belt-drive vs. direct-drive turntables.
and, later, Sound & Vision, have been blessed through the years with the reviews, columns, and features of a great many superstar experts. The list of prolific writers who have graced the magazine’s masthead as either a full-time or freelance editor is a who’s who of audio industry celebrities. Their collective contribution to the hobby simply cannot be overstated. If you’re a loyal reader for some time you’ll recognize these names: Julian Hirsch, David Ranada, Larry Klein, Ivan Berger, Tom Nousaine, and even longtime current contributors Ken Pohlmann and Daniel Kumin. Peter Mitchell, whose work we reproduce here, is another member of this accomplished group. At one time a contributor to several audio publications and the president of the Boston Audio Society, Mitchell brought a fact-based, engineering approach and a refreshingly clear writing style to both his feature stories and, later, his “High End” column that graced the back inside page of SR until his untimely passing. This article, which appeared in the July 1983 issue, was in the vein of so many of the helpful how-to and shopping stories in SR and S&V that attempted to teach while debunking the misinformation rampant among audiophiles. You’ll note that while some of Mitchell’s “myths” address dated technologies and constitute a nostalgic walk down memory lane, others—even his comments about vinyl—remain both relevant and timeless. Especially this: “To choose audio components, listen to them, not to theories and claims about them.” A real pearl, that one. — ROB SABIN
hopping for hi-fi components can be confusing enough even when you have all your facts straight. And if you subscribe to many of the common myths and misunderstandings about how audio equipment works, how specifications relate to what you hear, and what all of the technical jargon means, you’re really in trouble. Some misconceptions have their origin in misleading claims made by salespeople or in advertisements; others arise from the wondrously complex and subtle nature of the human hearing process, which inevitably gets involved in the judgments that people make about how good a stereo system sounds—or how they assume it ought to sound.
Let’s shoot down some of the hot-air balloons that continually arise in hi-fi, taking as our gospel the principle that there are exceptions to almost every rule. To choose audio components, listen to them, not to theories and claims about them. And remember that what you hear in any particular case may be influenced as much by the factor of compatibility—between a stylus and a tone arm, between an amplifier and a speaker, between speakers and room acoustics—as by the quality of individual components. If a system sounds good, it is good, regardless of theory. If it sounds bad, something in it probably is bad—but the fault may not be what you think it is. The twenty-one misconceptions discussed here, in no particular order, are among those we have found to be most common.
Weighted specifications are the audio industry’s way to cheat by making the numbers look better.
False. Weighting is an effort to make test equipment “hear” the way the ear does, so as to produce measurements that accurately predict what we will hear. For instance, A-weighted measurements of background noise correctly reflect the fact that at low volumes the ear is sensitive to even very small amounts of noise occurring at mid-treble frequencies (around 3 khz) while much larger amounts of noise at low bass frequencies are inaudible.
Okay, then, unweighted specifications are meaningless.
Wrong again. Although unweighted specs often don’t correlate directly with what we hear, they can alert you to other problems. For instance, if a turntable’s rumble is concentrated at frequencies below 10 Hz, where the ear can’t hear it, the DIN-Bweighted rumble figure is likely to be down around -60 or -70 db, correctly predicting that you won’t hear the rumble itself in playback. However, if the unweighted rumble figure for the same turntable were -30 db or worse, that could indicate unwanted stylus vibration that would be heard—not as rumble, but as flutter and mistracking. Similarly, if a product’s A-weighted signal-to-noise ratio (S/N) is good but the unweighted S/N is much worse, it may have excessive 60-Hz hum since A-weighting reduces the influence of any power-line hum on an S/N measurement. Records must be stored vertically, never lying flat. Only half true. Actually, once you understand that record vinyl is a congealed liquid that yields under pressure (like very thick molasses), the two primary rules of record storage will be obvious: (1) Records should be subjected only to light pressure; heavy pressure may press loose dust or wrinkles from the plastic liner into the vinyl
surface. (2) Any pressure should be distributed evenly over the disc; uneven pressure may cause warping. Thus, vertical storage is fine (really vertical, not leaning; fill empty spaces with cardboard). But horizontal storage on closely spaced shelves is also okay; you can stack up to a dozen discs on a level surface before the pressure on the bottom disc becomes too great. In either case, be sure that the discs’ jackets are not themselves warped or tight enough to cause warping.
A 60-watt amplifier will play 20 percent louder than a 50-watt amplifier, and a 100-watt amp will play twice as loud.
Nope. A 20 per cent increase in available wattage amounts to less than 1 db of increased loudness capability. Doubling the power input will give a 3-db increase in volume, which can be noticeable but is definitely not dramatic. It’s a matter of biology: our eyes and ears have an approximately logarithmic response to light and sound so that they can cope with the million-to-one range in iñtensities that they are exposed to. In any stereo system only 1 to 10 watts of power are actually used, on average, to generate “loud” sound levels with typical music. An amplifier’s ability to put out more power does, however, influence its sonic clarity, “openness,” and low-bass impact, especially during transient peaks and climaxes.
Any two 50-watt amplifiers should sound alike.
Well, sort of. Actually, a well-made 20-watt amp and a 200-watt amp will sound alike much of the time. But if you are concerned about those transients and climaxes that stress an amplifier’s capacity to the maximum, then the rated power is only a very rough guide because it is measured using an 8-ohm resistor instead of a loudspeaker. “Power” is the electrical product of both voltage and current. Two amplifiers with the same power rating usually have the same maximum voltage output, but they may have very different output current capacities, which can make an important difference in driving a loudspeaker that has a low or complex (“reactive”) impedance.
Moving-magnet (MM) phono cartridges are not as good as moving-coil (MC) cartridges.
As cartridges of both types continue to improve, the accumulating evidence indicates that it really doesn’t matter whether the magnet or the coil does the moving. In various comparisons among highperformance MC and MM cartridges— notably a set of carefully controlled listening tests supervised by Canadian researcher Floyd E. Toole—the audible differences in timbre and detail have consistently been related to the cartridges’ known differences in frequency response. When these differences were equalized, the MM and MC pickups sounded alike.
A component rated at 0.01 per cent total harmonic distortion (THD) will sound better than one rated at 0.1 per cent THD.
Biology again. Distortion generates false tones at frequencies other than those in the original signal. If these distortion components are sufficiently weak compared to the original signal, they won’t be heard. If you can’t hear them, reducing them still further below the threshold of audibility won’t make them any more inaudible. The actual threshold of audibility depends on the frequencies involved in both the original signal and the distortion. With musical signals of typical complexity, tests have repeatedly shown that distortion levels below 3 percent aren’t heard even by experienced audiophiles.
Sensitivity is the most important specification of an FM tuner.
Perhaps— if you are located more than fifty miles from your favorite station and cannot use a roof antenna. In the urban and suburban locations where most people in the U.S. live, however, signal strengths of several hundred microvolts are typical, and the usual problem is interference (due to multipath reflections or strong adjacent stations). Therefore, for the majority of FM listeners the really important
FM- tuner specifications are capture ratio, AM rejection, and alternatechannel selectivity.
Bass depends on woofer size.
A large woofer can always reproduce deep bass better than a small woofer. The problem here is to distinguish between quality and quantity. The quantity (the volume level) of deep-bass output is strictly dependent on the amount of air that is moved, which equals the area of the woofer cone multiplied by its “excursion” (backand-forth movement). Thus, a large woofer can reproduce bass at higher maximum volume levels; conversely, at a given high volume level, a large speaker can usually reproduce lower frequencies with less distortion than a small one can. But at moderate volume levels the deep-bass “reach” of a speaker is a matter of design choice; some 8-inch woofers have useful response down to 25 Hz while some 12-inch woofers roll off steeply below 50 Hz. Deep-bass response is not free: to extend the bass you must either reduce efficiency (thus requiring more amplifier power for those climaxes) or use a bigger, costlier cabinet.
A three-way speaker system is better than a two-way system.
The main advantage of a three-way system is higher power-handling: it can play louder without burning out its voice coils, a significant consideration if you are trying to re-create rock-concert sound levels in a very large room. The purely sonic advantages of a three-way design, however, are small in theory and sometimes nonexistent in practice. Particularly in the mid-price range of speakers, a system employing two high-quality drivers and a carefully tailored crossover often outperforms one
with three cheaper drivers and a complicated crossover. The proof, of course, is in the listening.
Separate components (tuner, 11 preamplifier, power amplifier) are better than an all-in-one receiver.
Sometimes yes, but often not. Separates offer greater flexibility, of course, and some include more elaborate circuits or features (selectable wide/narrow tuner i.f. filters, for instance) that can prove useful in special circumstances. Also, very few receivers offer more than 100 watts per channel, so users who need or want more power may have to go the separates route. But a few manufacturers have found it more cost-efficient to make integrated amplifiers and receivers using the same circuitry as in their separates; such a receiver actually consists of tuner and amplifier separates in a single housing.
A belt-drive turntable is better 12 than a direct-drive turntable, or vice versa.
Neither. The best examples of either type are superb. Among lower-priced units, each type has its strong and weak points. For instance, even a low-priced direct-drive system can easily be made to provide variable pitch and exact speed regulation. Belt-drive design, on the other hand, makes it easy to float the platter and tone arm on springs for isolation from internal and external vibrations. Take your pick.
13 Digital tuners are better than “analog” tuners.
The basic advantage of digital-synthesis tuning is its convenience: quick, precise, pushbutton selection of favorite stations. In terms of sensitivity and sound quality, though, the tuning method is irrelevant— except in those few digital tuners with inadequate internal shielding that allows noise and whistles from the digital circuitry to leak into the audio.
Chrome and metal tapes cause 14 more rapid head wear than ferric tapes tend to do.
This old canard has been consistently proved false in tests. Poorly made “bargain” tapes are the only ones likely to cause rapid head wear, and these, of course, are mostly low-grade ferrics. With good tapes from reputable manufacturers there is no clear correlation between tape type and head wear. (With all tape types wear does tend to increase with high humidity, though.)
Chrome and metal tapes have 15 more distortion than ferric tapes do.
This is true at high recording levels (0 VU and above), but the differences in distortion are slight. More to the point, at lower recording levels the distortion decreases rapidly to inaudibility with all tape types.
So, to make recordings on high-bias tapes that are as distortion-free as those on premium ferric tape, simply decrease your recording levels by about 2 db.
Playing a “normal” (ferric) tape 16 in the chrome (high-bias) position will damage the recording.
No way. During playback, mis-set controls may cause poor sound, but the signal on the tape won’t be altered— unless you accidentally set the deck for record and erase the tape!
Overloading a tape recorder 17 (by pushing its level indicators strongly into the red) may damage the machine.
Not even a little bit. Oh, it’s conceivable that you might bend a meter’s needles if you “pin” them hard enough, but even that is very unlikely. As for the recorder’s electronics, they can be damaged by connecting the 120-volt a.c. power line to an input jack but not by any authentic audio signal.
Tone controls should always be 18 set “flat” for the most accurate sound.
This might be a reasonable notion if every other element in the recording and playback chain (from microphone to speakers to room acoustics) were known to be “flat,” but of course that’s not so, at least not yet. Regardless of how good your playback system is, recordings vary a great deal in tone quality (sometimes because of equalization added to compensate for imperfections in the studio’s monitor speakers). In the absence of any objective standard of accuracy, it simply makes sense to use tone controls to obtain the sound that seems natural and lifelike to you.
Circumaural headphones (the 19 kind with a rubber ring that fits all around the ear, making an airtight seal) are better than the open-air types that simply rest on the outer ear.
Circumaural phones have two advantages: extended deep-bass response is easier to obtain, and the airtight seal efficiently excludes external sound (an important consideration in live on-location recording). Open-air phones tend to be more comfortable to wear and can sound equally good. In Stereo Review’s July 1982 listening tests of fifteen headphones, the three highest-ranked models were an open-air, a circumaural, and a quasi-circumaural design with a “leaky” foam ring instead of an airtight rubber surround. Evidently no one design approach is unequivocally the best.
20 Unlike discs, tapes don’t wear out with repeated playing.
They do, but in a less obvious way. With worn discs, noise and distortion are added to the sound. When tapes are played a great many times there are signal losses, dropouts and high-frequency rolloffs, caused by the rubbing and flexing of the tape as it is pressed against the deck’s heads, capstan, and guide posts. The highs may also be partially erased by residual magnetism in these metal parts, hence the need for periodic demagnetizing.
21 Digital Compact Discs (CDS) are virtually indestructible.
Not so. It is true that ordinary surface dust, fingerprints, and light linear scratches have little or no effect on them and that wiping a dirty CD clean usually restores pristine playback quality. But a curved scratch that follows the CD’S spiral signal path can make it unplayable. Therefore, when cleaning a CD, do not use the circular brushing motion that is customary with analog LPS; wipe the disc from center to edge. And remember that the CD’S signal surface is embedded directly beneath the label, protected only by a thin coating of lacquer. A scratch that penetrates through the label is likely to wreak more havoc than a scratch on the transparent-plastic-coated “playing” side of the disc.
Peter W. Mitchell, one of hi-fi journalism’s most prolific writers, is also president of the Boston Audio Society and of his own electronics consulting firm.