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STEREO DIRECTORY & BUYING GUIDE 1975
Herbst 1974 !!! Fast genau wie bei uns - nur auf Englisch

Es ist aber nur fast so wie bei uns. Denn Karl Breh hatte sich sowohl in der Hifi-Stereophonie als auch in den Hifi-Jahrbüchern viel mehr Mühe gemacht und diese Buchstabenwüsten geschickt illustriert. Das fehlt hier ganz.

Eine gute Gelegenheit, sauberes Englisch zu lesen

Ich habe den Text hierunten drunter absichtlich genau so übernommen, wie er in dem Heft von 1974 steht. Ein paar der Begriffe kommen mir zwar "spanisch" vor, aber sehen Sie selbst.

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Starten Sie ruhig mal mit einer richtigen Buchstabenwüste:

und geben Sie nicht gleich auf, wenn es scheinbar nicht mehr enden will, es gibt (am Ende) ein Ende.

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WHAT EVERY HI-FI SHOPPER SHOULD KHOW BEFORE BUYIHG

Erste Seite

A practical guide to selecting stereo and quadraphonic hi-fi components. BY JULIAN D. HIRSCH - Hirsch-Houck Laboratories - (vermutlich "summer 1974")
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Introduction - (Seite 9 von 162)

EVEN for the most knowledgeable audiophile, entering a well-equipped dealer's hi-fi showroom can be an overwhelming experience. Small wonder, then, that a newcomer to the world of high fidelity is often tempted to turn tail and flee when faced with row upon row of tuners, amplifiers, receivers, and tape decks, usually terminating in a complex switching panel that channels any selected output to a wall-to-wall, floor-to-ceiling array of loudspeakers!

Before panic sets in, stop to consider that a hi-fi system, from the simplest to the most elaborate, consists of only a few basic components. With the application of a little common sense and some study of the subject, it is easy to avoid incompatible combinations of equipment. Here are guidelines to making your shopping visits to audio dealer showrooms more rewarding.

  • Anmerkung : Wichtig ist, er hier spricht dauernd von Hifi-systems. Doch weiter hinten in der großen Übersicht der Geräte ist ein Haufen nicht Hifi tauglicher Geräte Müll aufgeführt, leider.


In its most basic form, a stereo music system consists of a program source (tuner, records, or tape), an amplifier, and two speaker systems. Depending on your location and personal preferences, you may choose to dispense with FM radio programming in favor of commercially produced records or tapes, or conversely may opt for "free" music "off-the-air" rather than a substantial investment in recorded music.

In some rural areas, inadequately served by FM, an AM tuner may be necessary. Most tuners and receivers provide both FM and AM reception, although AM quality is usually little better than that offered by a small transistor radio. In any case, it is adequate for news broadcasts, sports events, and "talk" shows.

Overview

Before getting down to the serious business of selecting the components for your music system, you should become familiar, in a general way, with the different categories of equipment and their place in the system. Later, we will go into more detail on each type of component, but first let us take a walk around that hypothetical audio showroom and examine its offerings.

Besides its basic function of amplifying (about which more later), the amplifier serves as a control center for the system and selects any of several program sources for your listening pleasure. Even if you initially purchase only a record player, other source equipment - a tape deck, for example - can be added at any later time without obsoleting your system.

You will notice, especially in the higher price and power brackets, that the amplifier is sometimes built as two separate units, called the preamplifier and the main amplifier or power amplifier. This is done principally to keep size and weight within reasonable bounds. A powerful amplifier may weigh 30 to 40 pounds or more and is correspondingly large.

By separating the control section (the preamplifier) from the heavy power amplifier, the latter can be placed out of sight, making for a more attractive installation. In the low- to- medium power range (say, up to 40 or 50 watts per channel) the power amplifier adds little to the bulk of the unit and the two sections are usually combined to form an integrated amplifier. Many manufacturers offer their amplifiers in both integrated and separated form, with the latter frequently having somewhat more control flexibility to justify their slightly higher cost.

About Dealers

One section of the dealer's display will be devoted to tuners. This is the part of the system that receives broadcast signals and converts them to an electrical form which can be processed by the amplifier and eventually heard from the speakers. Like amplifiers, tuners are available in a wide range of prices, with features and performance to match. You will recognize the tuner at a glance by its tuning dial (generally a large rectangular area on the panel, often "blacked out" when the unit is turned off, but colorfully lit when it is in use). Most tuners have only a couple of control knobs, in addition to the tuning knob.

You will probably find that the bulk of the electronic components on display are receivers, or combinations of tuner and amplifier in a single unit. The receiver is the most popular form of hi-fi electronic component, and for good reason. It occupies little more space than either a tuner or an amplifier, alone, and usually costs somewhat less than separate components of similar ratings.
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cost savings (in USA sehr wichtig : Geld sparen)

The cost savings are achieved, for the most part, by using a common chassis, power supply, and cabinet (if you price the wooden cabinets offered as accessories by many manufacturers, you will appreciate the economic advantage of using one cabinet instead of two!). Best of all, there is usually little or no sacrifice of performance or versatility in a good receiver, as compared to equivalent separate components.

Not long ago, record players were classified either as changers (or automatic turntables), or manual players.

Today, most automatic features are found on single-play turntables as well, so that fully manual record players are the choice of audio purists who prefer to "do it themselves" while the great mass of audiophiles use some form of automatic turntable, whether it be a changer or a single-play unit.

Tape recorders

Tape recorders (more properly called tape decks when they are used as a part of a high-fidelity system) can be classified as open-reel or cassette types. There are also units which will play 8-track cartridges (the kind used in automobile tape players) through a home music system, and a few which can make recordings on blank 8-track cartridges.

A few low-to-medium priced open-reel tape decks are still manufactured, but the bulk of that market is devoted to the more refined and expensive equipment, selling for $500 or more. At lower prices, the cassette is king, although there are several cassette decks selling for close to $500 and a couple of professional-quality units at even higher prices.

High-fidelity performance can be expected from a good cassette deck, especially when you record your own cassettes from radio or records. Lower priced models (under $150-$200) are often capable of surprisingly good quality, but lack the refinements of the more expensive decks.

Open-reel recorders are a "must" if you expect to edit your tapes (virtually impossible with cassettes) or if you will settle for nothing less than the finest, state-of-the-art sound quality.

Loudspeakers

And now we come to the loudspeaker, the most important part of a hi-fi system and unquestionably one of the most difficult to categorize from the standpoint of suitability for a particular installation or individual taste. You will find a greater range of price (and size) among loudspeakers than anywhere else in the high-fidelity scene. Excluding the many speakers whose sound falls short of high-fidelity standards, it is possible to spend less than $50 or more than $1000 for one speaker - and you will need two for stereo, or four for quadraphonic!

Unlike the other audio-system components, loudspeaker performance - the actual sound quality you hear in your home - varies drastically from model to model. It is almost literally true that no two types of speaker systems sound alike.

Unfortunately, no measurements thus far devised can do more than give a rough idea of a speaker's sound. Listening is the only way, which is why that solid wall of speakers faces you as you step into the dealer's demonstration room.

There are still a few pitfalls to watch out for. Since speakers tend to sound quite different when heard in different rooms, and some speakers sound their best only with certain kinds of music, it is all too possible to become completely "sold" on a particular model in the showroom, only to find it a disappointment in your own home. We will have more to say about speaker selection later.

There are many accessories that can add to the enjoyment and utility of your music system. Prominent among these are stereo headphones, whose popularity has grown with public awareness of "noise pollution." Headphones, like speakers, vary widely in sound, style, and price, with the additional consideration that they must be comfortable to wear.

Quadraphonic (vom Herbst 1974)

Four-channel (quadraphonic) sound is now an accepted part of the audio scene. We will deal with the special characteristics and problems of 4-channel in a later section, but for now it will suffice to know that a basic four-channel system must have four speakers, together with a four-channel amplifier (or two stereo amplifiers with an adapter unit). Stereo systems can usually be converted to 4-channel by adding another amplifier and adapter, plus the two rear speakers. Alternatively, you can start with a four-channel amplifier or receiver, using it as a stereo unit until you are ready to add the rear speakers.

Now that you have been introduced to the basic high-fidelity components, let us consider each of them in more detail.

STEREO Amplifiers

A LOUDSPEAKER, in order to produce sound, requires an input of electrical power, measured in watts. Program sources, including phonograph pickups, tuners, and tape decks, supply miniscule power levels (microwatts to milliwatts). The amplifier's task is to increase these weak signals to a level suitable for driving a loudspeaker.

How much power do you need? This is difficult to answer except in very general terms. It depends on the type of loudspeaker (the efficiency with which a speaker converts electrical energy to acoustic energy varies from a small fraction of one percent up to 10% or more), the size and furnishings of your listening room (a large room with upholstered furniture and carpets requires much more power than a small, sparsely furnished room), the type of music you favor (chamber music can be reproduced with less power than rock music, for example), and the listening volume you prefer (obviously, more volume requires more power).

As a rule, loudspeaker manufacturers will recommend a minimum amplifier rating (e.g, 20 watts per channel) which should give satisfactory results with their speakers in a "typical" listening room. If these recommendations are followed, you are unlikely to find yourself underpowered. However, it is better to err on the side of too much power rather than too little power. A "20-watt" speaker will probably sound better, even at moderate listening levels, when driven by a 60-watt amplifier than by a 20-watt amplifier, and there is usually no danger to the speaker from such operation.

An exception might be the pairing of a "super-power" amplifier (150 watts per channel or more) with small speakers intended for amplifiers of one tenth that rating.

Because of the interdependence of speakers and amplifiers, you should consider them together when planning a system. Don't worry about a discrepancy of 100%, or even more, between their power "ratings" - as we have said, they are very general in nature. Simply avoid a huge mismatch (10 to 1 or more, for example). Bear in mind that while a powerful amplifier can only enhance the sound of almost any speaker, an inefficient speaker can prove to be a severe disappointment if the amplifier is underpowered.

Amplifier Specifications "IHF" and "RMS"

Current advertising standards imposed by the Federal Trade Commission, effective November 1974, require amplifiers to be rated with all channels driven simultaneously, under standarized test conditions. Older specification sheets may be in circulation for some time with other types of power rating systems, such as IHF Dynamic Power, Music Power or Peak Power. Be careful when comparing amplifier ratings to use only the continuous power (sometimes erroneously called "RMS" power) figures. All stereo review amplifier tests conform to the new FTC requirements.

What about the power bandwidth and distortion specifications, also required by the FTC ruling? The power available from an amplifier typically is less at the upper and lower extremes of the audio band (generally considered as 20 Hz and 20,000 Hz) than in the middle, around 1000 Hz. An amplifier must be able to deliver its rated power, at the advertised distortion level or less, over its specified bandwidth limits.

It is probably not necessary to develop rated power at 20 Hz and 20,000 Hz, but we would consider a power bandwidth of 40 to 15,000 Hz to be a minimum for a true high-fidelity product. Incidentally, power bandwidth as defined by the FTC is not the same as the old IHF power bandwidth standard, and there is no simple relationship between them.

The audible effects of various distortions are debatable but, by current standards, a distortion of 1% at rated power would be reasonable for a lower priced amplifier, with the medium priced units typically rated at 0.5% or less. The finest amplifiers carry distortion ratings as low as 0.1%.
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Amplifier Controls

Every amplifier (and preamplifier) has a number of controls which allow you to modify the sound to suit your taste. Tone controls typically increase or reduce the level at low frequencies and high frequencies, with little or no effect on the mid-range. Most good tone controls use negative-feedback circuits (sometimes called Baxandall circuits, after the British engineer who introduced them some years ago). These have the capability of controlling response only at the frequency extremes, where correction is most often needed, with less mid-range interaction than non-feedback controls. There is a trend, in the middle and high price brackets, to provide additional tone-control flexibility. This may take the form of a third "mid-range" control, or of a choice of several switch-selected turnover frequencies beyond which the control action begins. One manufacturer provides two additional controls, whose effects are confined to the extremely low and high frequencies.

The ultimate in versatility is offered by graphic equalizers, which have individual adjustments (usually sliders, whose positions suggest the overall response shape, hence the term "graphic") for each of five to ten continuous frequency bands covering the entire audio range.

The utility of tone controls and equalizers increases in proportion to their complexity (and cost). Many people - perhaps most - will be perfectly satisfied with a basic two control system, but for those who know what they want to hear, the more complex controls are well worth their extra cost. Most tone controls, incidentally, affect the left and right channels of a stereo system simultaneously, which is quite satisfactory when both speakers are identical (as they should be). Some amplifiers have separate controls for left and right channels, which is a nicety, but not of much practical significance.

Other "frequency-contouring" amplifier controls include loudness compensation and filters. The former boosts the low frequencies (and sometimes the highs as well) relative to the mid-range when the volume control setting is lowered. Ostensibly this is to preserve a correct audible balance among all frequencies at low volume levels, where the ear loses sensitivity to the frequency extremes.

The majority of such compensation systems fall far short of their objective, usually imparting a heavy and unnatural quality to the sound. They can be switched out, however, so that you can follow your own inclination with respect to this feature. Occasionally an amplifier or receiver appears with non-defeatable loudness compensation. Such a product is unsuitable for high-fidelity use.

Filters, which are found in most amplifiers, attenuate the low-frequency and high-frequency response to reduce turntable rumble, record scratch, and similar unwanted noises. Most of them are of little value, due to their gradual cut-off slopes (6dB level change per octave of frequency) which cause them to remove as much of the program as they do the noise.

Tone controls usually are at least as effective for this purpose. There are some exceptions, generally in the higher priced equipment. Look for a specification of 12dB per-octave filter slopes if you expect to make effective use of audio filters.

The input selector switch, mentioned previously, will have a minimum of three positions, for Phono, Tuner, and Aux sources. The latter (from Auxiliary) can be used for an extra tape deck, tuner, TV sound, or other high-level program source. The Phono input connects the pickup output to a special amplifier that raises its level to approximately the one volt of a typical high-level input, and also equalizes it to obtain flat frequency response when playing records.

Amplifier specifications usually include a phono sensitivity rating (such as 2.5 mV) which is the signal level required from the pickup (at 1000 Hz) to drive the amplifier to its rated power. The range of pickup outputs and amplifier sensitivities is relatively small, so that almost any currently available pickup and amplifier should be compatible in this respect. One item not always found in amplifier specifications is the phono overload input. A high-output cartridge, playing a record with very loud passages, can overload some amplifiers, even with the volume turned low, and cause distortion. An overload rating of 50 mV or higher is desirable, especially if your cartridge has a rated output greater than 5 mV.

Other amplifier features may or may not be of importance to you. These include switching for two or three sets of speakers, tape dubbing connections for copying from one tape deck to another, and additional input capabilities. Some deluxe amplifiers can handle two phono
pickups and two or three tape decks, plus two to four other high-level sources. All high-fidelity component amplifiers should have a Tape Monitor switch, which allows you to connect any selected program to a tape deck, while simultaneously listening to the playback of the same program from the recorder. The Tape Monitor circuit is important even if you do not expect to use a tape deck, since it can be used to connect external accessories such as quadraphonic adapters, equalizers, noise reduction devices, etc.

Almost every amplifier has a headphone jack on its front panel, suitable for driving any stereo headphone except electrostatic types. The microphone inputs offered on some models are of little value unless you plan to use the amplifier for public address announcements as well as hi-fi listening.

Check the back of the amplifier to see if it has enough a.c. outlets for the other parts of your system. At least two outlets, one of them switched, are highly desirable if you expect to use a tuner and a record player in your system.

AM-FM Stereo Tuners

The tuner is the "radio" portion of your music system. Although most tuners cover the AM and FM broadcast bands (and proposed government legislation now makes this mandatory), the following comments apply specifically to FM tuners.

The tuner's function is to separate one desired signal from the many intercepted by the antenna, amplify it millions of times, convert its frequency modulation to an exact facsimile of the original program, and (if it is a stereo program) subject the detected signal to a complex process which separates it into left and right stereo channels.

Like amplifiers, most tuners tend to sound pretty much alike on ordinary program material. Many people place great store on such specifications as sensitivity and selectivity. Actually, neither of these is easy to reduce to a single convenient number that defines that aspect of the tuner's performance. They are used in that manner, of course, but as a result are frequently misunderstood or misinterpreted.

Sensitivity refers to the ability of a tuner to receive a weak signal with acceptably low noise and distortion. The IHF Usable Sensitivity rating is most often quoted, although it does not correspond to a really listenable signal. Most good tuners have an IHF sensitivity of less than 3uV, and some are as low as 1.5uV. Although in practice it would not be possible to detect any real difference between two tuners whose sensitivities differed by a factor of two (all else being equal), there is a tendency to make much of differences of a few tenths of a microvolt, which are quite insignificant.

More meaningful is the 50dB Quieting Sensitivity rating included in a new IHF tuner standard, but not yet in wide use. Our test reports in stereo review do include it, however. This is usually in the range of 3 to 7uV and represents the weakest mono signal that can be received without excessive background hiss. For stereo reception, all these sensitivity figures should be multiplied by a factor of ten, which may explain why stereo sensitivity ratings are not widely publicized!

Of course, these sensitivity numbers have no absolute meaning to the consumer who cannot know the actual received signal strengths in his area. In rural locations, one can indeed find signals of a few microvolts, and sometimes the highest possible tuner sensitivity is needed in such locations. At most urban and suburban locations, the tuner receives hundreds or even thousands of microvolts from the antenna from dozens of stations.

Clearly, high sensitivity is not likely to be an important tuner rating for the city dweller. What about selectivity? FM channels in any given area are assigned at 400-kHz intervals (alternate-channel spacing). If you are located close to a powerful FM station and wish to receive a far-off station only 400 kHz removed, you will need high alternate-channel selectivity. Most FM tuners have selectivity ratings between 45 and 60 dB, which is generally adequate for interference-free reception. If you have a "problem," there are some tuners whose alternate-channel selectivity is 90 dB or more. They are expensive, but well worth it if you need their special qualities.

In strong-signal areas, some tuners are subject to spurious responses -signals appearing on the dial in unexpected places, and sometimes interfering with a desired signal. The relevant ratings - image rejection, spurious rejection, i.f. rejection - are also expressed in decibels, with the higher numbers being better.

A major cause of distorted FM sound is multipath reception, caused by a signal reflecting from various structures and reaching the antenna from different directions and at slightly different times. The tuner specifications related to low multipath distortion are capture ratio (the lower the better, with most good tuners under 3dB and the best reaching 1dB or less), and AM rejection (ratings in excess of 50dB are good, and a few are as high as 70dB). You should be aware that no tuner can be completely immune to multipath distortion and that the best cure for this and most other FM reception problems is a good directional antenna which can be rotated to obtain best results.

The tuner distortion rating should be well under 1%, and most good tuners are rated between 0.2% and 0.5% in mono, and about twice as much in stereo. Stereo channel separation varies with modulating frequency, but is often specified at 400 Hz or 1000 Hz, where it is greatest.

Comprehensive ratings include a definition of separation over a range of frequencies, such as 100 to 10,000 Hz. If the separation exceeds 20dB over most of the audio range, you can be assured of a satisfactory stereo effect. Many tuners in all price ranges have 30 to 40dB of separation over most of the audio band.

Many important tuner differences relate to their ease of operation, rather than to their electrical performance. The tuning dial should be legible and well calibrated (some tuners, even high-priced units, are difficult to set accurately to a known frequency because of inadequate dial calibration). The tuning "feel" should be smooth and
positive. Tuning indicators, whether meters or lights, should give an accurate indication of correct tuning. Interstation noise muting circuits should be free from bursts of noise as one tunes through a station (although many are not). All of these characteristics are easy to judge for yourself and require no technical knowledge.

There are several tuners with digital frequency readouts instead of the usual mechanical dial system. This eliminates any problems of dial calibration but adds appreciably to the cost of the tuner. Compensating for their higher prices is the fact that most digital tuners also have above average performance in most other respects.

STEREO Receivers

EVERYTHING in the preceding sections applies with equal force to the receiver, which is a combination tuner and amplifier. Some receivers even have separate preamplifier outputs and power amplifier inputs, making them the equivalent of a three-piece combination of separate components.

In general, receivers sacrifice little or none of the flexibility of separate components. Some deluxe models, for example, have provision for two or three tape decks and can dub from one to another through their internal circuits.

Are there any valid objections to the use of receivers? Perhaps their only operational limitation is imposed by size and weight considerations, which make it impractical to provide the huge power outputs found in some power amplifiers. The limited space available for power-supply components sometimes restricts the maximum power output at the lowest audio frequencies. Nevertheless, some of the newer receivers can hold their own against any separate amplifier in this respect.

While most receivers are moderate powered (say, up to 40 watts per channel), the upper limit has been steadily increasing and 60 watts per channel or more is available from a number of receivers. A couple of the top units can approach 100 watts per channel.

Since the total power available from a receiver is ultimately limited by the power supply, it is usual for four-channel receivers to have about half the power per channel that can be gotten from two-channel receivers of comparable size.

By a novel circuit connection known as "bridging" or "strapping," some manufacturers of four-channel receivers combine the outputs of the front and rear amplifiers to more than double the power per channel in the two-channel stereo mode. Using this technique, a couple of the heaviest four-channel receivers actually deliver 130 to 150 watts per channel in their stereo connection.

What about the possibility of obsolescence of an expensive receiver, which cannot be up-dated piece-meal? This is actually a "paper tiger," since the performance and flexiblity of any receiver rival those of comparably rated separate components. It is difficult to imagine any technological change which would obsolete a modern receiver, unless it were so drastic that all high-fidelity components were made obsolete.

Even four-channel FM broadcasting, should one of the several proposed systems be accepted by the FCC, would probably be compatible with the special detector outputs built into many tuners and receivers.

One of the few real drawbacks to the use of a receiver, especially a high-powered unit, is its bulk. Shelf mounting is out of the question for most receivers and some of the larger units require a large, sturdy supporting surface.

On the other hand, most of the maze of system wiring is eliminated, together with the possibility of intermittent or noisy connections. Only the speaker leads, the record player or tape deck cables, and the antenna need be connected to the receiver to have a complete, fully functional high-fidelity system.

RECORD Players (Turntables)

A RECORD player consists of a turntable, a tonearm, and a cartridge. The turntable rotates the record at a constant speed, usually 33 1/3 or 45rpm, while the arm holds the cartridge as its jewel stylus follows the spiral groove on the disc. The cartridge, in turn, translates the microscopic "wiggles" of the groove walls into minute electrical signals which correspond to the recorded program and which are suitable for amplification.

Beyond these basic similarities, record players are highly diverse in their design and operating details. Most people use automatic record changers, which can hold a stack of six to ten discs (usually required to be of the same size and speed) and play them in sequence.

Record changers whose quality meets high-fidelity standards (usually referred to as automatic turntables) generally have interchangeable center spindles for multiple and single-play operation. Many people prefer to change records manually, while retaining the convenience of automatic arm indexing and end-of-play shut-off.

At the opposite extreme is the classic manual record player. After switching on the turntable, the user positions the arm by hand and places the stylus in the desired groove. At the end of play, the pickup must be returned to its rest and the motor shut off manually.

Few single-play turntables today are completely without automation. Many are designed to turn on the motor when the arm is lifted from its rest. Others shut off after play, sometimes raising the pickup from the record.

Finally, there is a strong trend to what might be called an automatic single-play turntable, which operates exactly like a record changer except that it does not change records.

A good turntable should have a constant (and accurate) speed, free from momentary wavers and fluctuations. It should be unaffected by reasonable line voltage changes or how many records are on it. Depending on their rate of occurrence, these short term speed changes are described as "wow" or "flutter," and produce the audible effects suggested by their names. Vibrations, from the motor or other sources, must be kept to a minimum and in any case must not be allowed to move the arm or cartridge, relative to the turntable platter. The result of such movement is called rumble, a low-pitched sound that sometimes can be heard during quiet passages in the music. If lifting the pickup from the record does not stop the sound, it is power-line hum rather than rumble.

Wow, flutter, and rumble are minimized by careful assembly and precise mechanical tolerances in the turntable and its drive system. Such methods are expensive, with the result that with turntables we find a definite correlation between price and quality.

Heavy "platters," which may weigh as much as nine pounds, also contribute to low flutter and rumble. However, one cannot assume that a turntable with a light platter is inferior to one with a heavier platter, since many other factors are involved. Low-speed motors are used in many of the better single-play turntables, since their vibration rates place the rumble components below the audible frequency range.

Perhaps the ultimate turntable design is the direct-drive motor offered by a number of manufacturers in their top-of-the-line record players. The electronically controlled motor rotates at the record speed, eliminating the need for belts and idler wheels and reducing rumble and flutter to nearly unmeasurable levels. Direct-drive turntables are expensive - $300 to $400 - but appear to offer the closest approach to ideal performance.

Rumble is expressed in decibels, relative to a standard recorded level, and is sometimes weighted to allow for the relative audibility of different vibration frequencies.

Low-priced record changers may have unweighted rumble levels of -20dB to -30dB, while the better automatic turntables typically measure in the -32dB to -38dB range. The rumble of the finest single-play turntables may be as low as -45 to -50dB. With audibility weighting, this becomes -50to -55dB, while the best direct-drive units may measure as low as -60 to -65dB. Since there is more than one standard of measurement, be sure that you don't compare "apples with oranges." Popularly used standards include NAB and DIN.

Flutter and wow are measured by the percentage of frequency modulation they impart to a constant-frequency recorded tone. A low-priced turntable may have as much as 0.25% flutter, which can be objectionable with many types of sustained music, but most reasonably good units measure 0.15% or less. The finest turntables have as little as 0.05% flutter and wow.

The tonearm and cartridge characteristics are closely related, although most arms are designed to accept any cartridge having the standard 1/2" mounting centers. A good arm should be balanced by a counterweight and have low friction pivots. The precision of the arm design and assembly becomes increasingly important as we go to lower cartridge-tracking forces.

Expensive, highly compliant cartridges, which can operate as low as 1 gram, can only be used in arms of the highest quality, such as those
in the most expensive automatic turntables or their equivalent in separate tonearms.

Many record changers selling for less than $100 are compatible with cartridges designed to track in the 2 to 3 gram range.

Almost all good arms now have anti-skating compensation, which corrects for the lateral forces developed by friction between the stylus and the record material. Cueing lifts are also in general use. The better ones are damped for a slow and smooth movement as the arm is raised or lowered. If you prefer to position the arm manually, check to see that the finger lift is easy to use (some are rather clumsy) and that the cueing lift does not allow the arm to drift outward as it descends under the influence of the anti-skating force.

With a conventional tonearm, pivoted at one end, the cartridge can be tangent to the record groove at only two points on the record surface. Tangency is a requirement for low distortion, but fortunately any well-designed arm will have an insignificant tracking error. Tracking error, in theory at least, can be completely eliminated by special arms which change the cartridge angle as it moves across the record, or by radial arms whose motion matches that of the recording cutter.

These techniques work as claimed, although their benefits are not likely to be audible to most listeners. The radial arm, which is not available on automatic players, has the more important advantage of freedom from skating force and therefore requires no anti-skating compensation.

The phono cartridge converts the movements of a diamond stylus tracing the record groove modulation to electrical outputs. In the interests of retarding wear of the soft vinyl record and the diamond stylus, a low vertical force is desirable. This goes hand-in-hand with a light and relatively delicate stylus system so that the best cartridges tend to be somewhat fragile and should be handled with reasonable care (their use in children's phonographs is definitely not recommended).

Almost all hi-fi cartridges are magnetic types, although there are a number of design differences among them. The audible differences between most competitive cartridges in a given price range are usually subtle, but many people nevertheless have definite preferences.

The improved clarity and freedom from distortion of the top-quality cartridges, which are priced between $50 and $100, are easily audible by comparison with the budget-priced units in the $15 to $20 range. But, as we have shown, their use is restricted to the better quality tone-arms.

It is impractical to select a cartridge on the basis of its electrical specifications, such as frequency response or channel separation, since almost all cartridges sold for high-fidelity use have essentially identical specifications! The best clue to cartridge quality (other than listening to it, which is really the best way to make a judgment) is the recommended range of tracking forces. In most cases, a cartridge rated for operation between 3/4 gram and 1/2 grams will be of higher quality than one with a 2 to 3 gram rating. Do not place too much emphasis on the lower figure of a range of forces, since no cartridge will deliver its best performance at its minimum force.

Very few cartridges are capable of proper operation at less than 1 gram, and then only in the finest arms. On the other hand, avoid using cartridges with rated forces exceeding 3 grams, since this is an indication of a relatively massive and stiff stylus assembly which usually has limited tracking ability.

The stylus tip may have either a spherical or elliptical shape. A spherical stylus with a radius of 0.7 mil (0.0007") is optimum for playing most stereo LP records. The elliptical stylus may have a smaller edge radius of 0.2 to 0.4 mil, which allows it to trace the higher recorded frequencies more accurately, together with a radius across the groove width of 0.7 and 0.9 mil so that it maintains proper contact with the groove walls.

Many people feel that the elliptical stylus provides slightly better sound on stereo records and it is generally agreed that it is superior to the 0.7-mil spherical stylus for playing older mono LP discs. On the other hand, it is more expensive and may not be worth the added cost when a choice is offered. The best cartridges usually come equipped with elliptical styli, however.

THE tape recorder

THE tape recorder is an active, creative part of a music system, which probably explains its unique appeal to the general public as well as to audio hobbyists. The ability to make your own high-quality recordings, either "live" or by dubbing, has a powerful attraction for many people.

As compared to phonograph records, cartridge and cassette tapes have a clear advantage in size and convenience of use. Open reel tape has a slight size advantage over records, but is clumsier to handle. Prerecorded tapes of any kind are considerably more expensive than records and their quality is usually below today's disc standards.

For the audiophile who makes his own tape recordings, the choice lies between cassette and open-reel formats. There are a few 8-track cartridge recorders which are suitable for making your own tapes to be used in automobile players, but most of them cannot match the quality of the other tape formats and are much less convenient to use.

For years, the open-reel format was the only one used in home tape recorders. Most home machines record and play back on four parallel tracks across the 1/4" tape width. Stereo machines use two tracks at a time and when the reels are interchanged after one pass and run in the other direction, the other tracks are used. Four-channel recorders use all four tracks on a single pass of the tape.

Standard tape speeds of l-7/8, 3-3/4, and 7-1/2 inches per second (ips) are used in most home machines. Sometimes the slowest speed is omitted and on a few high-quality recorders is replaced by 15 ips. In general, quality improves with increasing tape speed, but in practice the full potential of most home machines can be realized at 7-1/2 ips, and sometimes even at 3-3/4 ips. The higher speeds are easier to edit and have a higher dynamic range, making them preferable for live recording.

Some "semi-pro" recorders, which usually have the 15ips speed, can also accommodate the 10-1/2" professional size reel, but the 7" reel is generally used in non-professional recording.

Most open-reel recorders have three heads (erase, record, and playback) with separate recording and playback electronics. This lets you monitor a recording through the playback head an instant after it was recorded, using the tape monitoring facilities found in almost all amplifiers and receivers.

Lower priced open-reel transports (under about $400) usually use a single motor to drive the capstan and the reel hubs. At higher prices, it is usual to find three-motor transports, frequently controlled by electro-mechanical solenoids. Three-motor transports generally have lower flutter, gentler tape handling, and higher fast-forward and rewind speeds. Many solenoid-operated transports can be operated through remote-control accessories.

As with record players, a good tape transport should have less than 0.15% unweighted flutter. Typical single-motor transports have between 0.1% and 0.15%, while a good three-motor machine may have as little as 0.07% or even 0.05%. The noise level (referred to a signal level which produces a playback distortion of 3%) is likely to be from -45dB to -55dB, depending on the specific machine and the tape speed. The finest home recorders reduce noise to the -65dB or -70dB range. A few high-priced recorders have built-in Dolby noise reduction circuits, but their effect is less obvious (and less needed) than in cassette recorders with their inherently higher noise levels.

A cassette recorder is a miniature of an open-reel machine, with the tape and both "reels" encased in a small plastic cassette. The tape is about half the width of open-reel tape and runs at 1-7/8ips - a combination of circumstances which would seem to forever consign cassette recording to the "lo-fi" category. Happily, this is not the case.

Special cassette tapes have been developed which can store more energy in their magnetic coatings (especially at high frequencies) than contemporary open-reel tapes. In addition, improved tape coatings and manufacturing techniques have greatly reduced the "dropouts" and amplitude irregularities that plagued early cassette tapes. Finally, the mechanical design of the cassette itself has been improved so that jamming and tape breakage are relatively rare (at least, among high-quality cassettes, which are the only kind an audiophile should be using).

Simultaneously with the tape developments, recorder manufacturers have created new heads, featuring extended frequency response and longer life. One of the supposedly inherent limitations of the cassette medium was the provision for only a single combined record/playback head, contacting the tape through a small opening in the cassette. Since the design parameters for recording and playback heads are different, a compromise is necessary when the functions are combined. Now, ingenious recorder designers have found ways to insert a separate playback head into the tiny access opening, and three-head cassette recorders with full off-the-tape monitoring capability and professional quality are available (at a rather high price, however).

Cassette recorders have been criticized for their relatively high flutter level. Actually, this reputation was earned by some of the early cassette transports, but seems to have lingered on long after the problems have been corrected. In recent years, good-quality cassette transports have usually had flutter percentages between 0.15% and 0.2%, and much of the time these did not offend the ears of the listeners. However, there are a number of people who can detect, and are disturbed by, flutter levels of 0.1% or less. For these sensitive listeners it would seem that cassettes were out of the question.

A number of cassette decks we have tested recently, however, have shown less than 0.1 % flutter, with a couple reaching 0.07% and rivalling good open-reel machines. True, this caliber of performance is found only in relatively expensive machines, but there are many in the $200 to $250 range which should satisfy most users.

With a cassette recorder, the Dolby system is a necessity. Boosting the high frequencies at low signal levels during recording, and reducing them by the same amount during playback, the Dolby system improves the S/N ratio by 8 to 9dB. This can make the difference between good hi-fi quality and a "hissy," sub-standard recording.

If a cassette deck lacks the Dolby system (as most under $150 do), it can be added externally. However, it is probably more eonomical, and certainly more convenient, to buy a recorder with the circuits built in.

You can expect a cassette recorder without Dolby to have a noise level of -40 to -50dB, while the better Dolby decks can achieve a-60 to -65dB or even lower noise level, again rivalling a good open-reel recorder.

Almost all good cassette recorders have a reasonably flat response from 50 Hz to 12,000 Hz with good low-noise tape. They often reach 15,000 Hz or higher with chromium-dioxide tape or the new dual-layer tapes which do not require special biasing. In practice, these frequency limits match the program bandwidth of phonograph records and FM broadcasts, which helps to explain why a cassette recorder can usually make "perfect" copies from these sources.

8-track cartridges

Although 8-track cartridges have the potential for true hi-fi performance, their major use is in automobiles where wide frequency range and low noise are not necessary. As a result, little effort has been made to improve either cartridges or players, except in areas affecting reliability.

An 8-track cartridge contains a single pack of tape, which is pulled out from the center and rewound on the outside of the pack. This requires careful assembly of the cartridge, and specially lubricated tape, to insure reliable and jam-free operation. Some cartridge transports have a "fast-forward" mode, which advances the tape at 3 to 5 times its normal 3 3/4 ips speed. However, rewinding is impossible, making location of a specific portion of the tape a cumbersome and lengthy process. Editing is impossible.

In spite of these inconveniences and limitations, many people prefer to record their own cartridges, giving them a wider choice of programs for their cars as well as at home. Although the limited frequency response and high noise level of most cartridges cannot be heard in a moving car, they are only too audible through a good home music system. Recently, one company announced a new deluxe 8-track cartridge deck, using a special "Scotch" cartridge tape and having built-in Dolby circuits, which appears to have specifications rivalling those of a good cassette recorder. As the new tape becomes generally available, we can expect improved recorders from other manufacturers as well.

Loudspeakers

THE loudspeaker is the most important component of a hi-fi system and often the most expensive. But its performance is very difficult - perhaps impossible - to define in objective yet meaningful terms. The frequency response, distortion, and noise levels of most other system components can be measured accurately and, in any case, are so nearly ideal that the differences between competitive units are relatively subtle.

On the other hand, anyone who has compared the sound of different loudspeakers knows that few of them sound alike and that the variations in listening quality are often very large even within the same price class.

Clearly, speakers have not yet attained the degree of refinement found in other components. In fact, there is no consensus as to exactly what characteristics an ideal speaker should have! This situation does not necessarily place the shopper at a disadvantage since it gives him a chance to express his individual taste in sound when selecting a speaker system.

Most speakers radiate their acoustic output in a forward direction, facing the listeners. There is a tendency for the higher audio frequencies to "beam" so that they are heard at full strength only in a limited region in front of the speaker system. Some of the methods employed to disperse all frequencies equally through the listening area include using multiple speakers oriented in different directions, hemispherical convex dome radiators, and acoustic lenses (and combinations of these techniques).

Omnidirectional (or quasi-omnidirectional) speakers have enjoyed considerable popularity in recent years. They often have a spacious, open quality which is considered by many people to give a more convincing illusion of a live musical performance. Others claim that the stereo image is blurred by omnidirectional speakers. Obviously, this is a controversial subject - listen for yourself, and be assured that, whatever your decision, you will have plenty of company!

It is agreed by all that a single conventional cone speaker cannot cover the full audio range adequately. If it is large enough to radiate the low bass frequencies, it will have a sharply beamed and attenuated treble response. In addition, the output in the important middle frequency range will be irregular, adding a coloration to the sound. For these reasons, it is customary to divide the audio band into two or more segments, each radiated by a separate driver unit (sometimes with more than one effective in a certain frequency band). A crossover network channels the various frequency ranges to the appropriate drivers.

Most speaker systems are either two-way or three-way systems, although a few split the audio band into four segments. There is some disagreement among speaker designers over the optimum number of frequency bands in a multi-way system, but excellent speakers are available in each of the above categories.

Even those manufacturers who use crossover networks consider them a necessary evil. One very popular speaker system avoids crossover problems completely with a number of small cone drivers handling the full frequency range and reflecting most of their output from the wall behind the speaker. The dispersion of this array is not far from omnidirectional and its frequency response characteristics are corrected by an active equalizer that boosts both low and high frequencies in the amplifier section.

Reproducing each portion of the audio spectrum presents its own unique problems. For the low bass, there must be a compromise, or "trade off," among size, efficiency, and the lower frequency limit. Small bookshelf speakers are available with outstanding bass performance (down to 30 Hz in some cases), but a price is paid in efficiency, so that more amplifier power is needed for a given sound level. Other speakers of the same size have a higher efficiency, but sacrifice their response below about 50 Hz to achieve this. For many people, this is a worthwhile trade-off, since most music has little content below 50 Hz, but it is one of the factors which must be considered when planning a hi-fi system. Of course, it is possible to have high efficiency and deep bass response, but this calls for a large speaker enclosure.

At the high frequencies, the basic question is how to start and stop the motion of the cone or radiating surface in a very short time. Low moving mass is important, hence the widespread use of tiny "tweeters" less than one inch in diameter, even with the largest enclosures. For many years, electrostatic speakers have been used for tweeters, since they have many of the properties of an ideal reproducer. However, they are directional, and are fairly expensive. A recent speaker design uses a very light array of ribbon conductors in a powerful magnetic field to produce a very uniform and well dispersed output up to super-audible frequencies.

"exotic" speaker systems

A few speaker manufacturers produce what might be termed "exotic" speaker systems, unconventional in appearance and performance, and sometimes quite expensive.

As we pointed out earlier, the speaker efficiency and amplifier power ratings must be coordinated. Once you have established an approximate efficiency category, listen to a number of speakers to get a "feel" for their distinctive sound qualities. Try to use your own records, rather than a dealer's demonstration material (which can mask certain speaker defects or enhance their positive qualities). When you find a sound that pleases you, even if the speaker is beyond your budget, listen to less expensive speakers from the same manufacturer. Usually, a manufacturer's concept of good sound will be carried through his entire product line. At times you can get most of the qualities that attracted you to a $400 speaker in a $ 100 unit from the same company.

When comparing speakers, be sure that their sound levels are matched. Even a slightly louder sound can give the impression that a speaker sounds "better." See that the amplifier tone controls are "flat" and that the loudness compensation is switched off. Listen at levels you find comfortable and to the kind of music you prefer.

Try not to be unduly impressed by "flashy" sound, such as sparkling highs or thudding bass. A really good speaker, in any price range, is usually rather unassuming (sonically speaking), so that it becomes easy to forget that you are listening though a loudspeaker. If this happens to you, the chances are that you have found the "best" speaker for you!

HEADPHONES

HEADPHONES share many of the properties of speakers, in that they all have different sound characteristics which are difficult to define by measurements because the actual acoustic output of a phone is a function of the dimensions of the wearer's ear cavity. Fortunately, the subjective intimacy afforded by headphone listening is powerful enough to override whatever weaknesses they may have.

The conventional stereo headphone has a small dynamic loudspeaker in each earcup, with the necessary acoustic treatment to provide a smooth frequency response when coupled to the listener's ear cavity. Padded or liquid-filled ear cushions provide a tight seal on the wearer's head, which is necessary for good bass response. They also exclude ambient room noises, giving the headphone listener near-total isolation from his acoustic environment.

Another type of headphone is the non-isolating, or open-air, phone. Its earpieces are separated from the wearer's head by porous foam pads, which do not isolate the wearer from room noises or the other occupants of the room from the headphone sounds. Open-air phones not only have a distinctive, natural quality, but are very light and relatively comfortable to wear for long periods.

A variation on the standard dynamic phone is a "two-way" phone, with separate drivers in each earpiece for low and high frequencies. Some phones have individual volume controls on the earpieces, which can serve as a volume or balance adjustment. Electrostatic headphones are acknowledged to be the most accurate reproducers, surpassing even the finest loudspeakers in their smoothness and frequency range. However, electrostatic phones tend to be heavy, expensive, and limited as to the maximum sound level they can deliver.

One should not expect the same listening experience with headphones as with loudspeakers. Headphones, even the non-isolating types, remove the listener from his surroundings and compel him to be attentive to the music. No headphone sounds like a speaker, but must be enjoyed for its own special qualities. Since some people find headphones tiring to wear for extended periods, it is important to try them on for fit as well as sound before making a purchase.

Most headphones have a nominal 8-ohm impedance and will operate satisfactorily when plugged into the headphone jacks on any hi-fi component. However, there are some headphones with a higher impedance, between 150 and 2000 ohms, which are usable with receivers and amplifiers, but may not have enough volume when used with a tape deck having a headphone output.

FOUR-CHANNEL quadraphonic

FOUR-CHANNEL, or quadraphonic, sound is an extension of stereophony, in much the same manner as stereo evolved from mono. By recording and reproducing through four program channels, an added sense of depth and spaciousness can be imparted to the music. Also, it becomes possible to write or arrange music to be heard from different directions with the listener in the center of the stage. Although not what most of us are used to hearing, this is a legitimate musical experience which is made possible only by four-channel recording and reproduction.

Four-channel tape recordings have been with us for many years, although an insignificant number of commercially recorded four-channel tapes is available (in open-reel form, at least). However, a growing number of four-channel tape decks is appearing on the market and we can probably expect new tape releases to follow this trend.

Most four-channel tapes are in the form of Q-8 cartridges, playable on home or car cartridge decks which are designed for their use (these can also play the more common stereo cartridges). The Q-8 cartridges have all the advantages and disadvantages of the cartridge format, but the sonic impact of four-channel reproduction often overshadows any deficiencies in the tape system.

Theoretically, four-channel cassettes should be possible, but a combination of technical and patent licensing problems has so far blocked the entry of cassettes into the four-channel tape market.

Phonograph records dominate the quadraphonic scene and will probably continue to do so. Matrix records, such as Columbia's SQ and the Sansui QS system employed by a number of smaller record companies, can provide a moderate-to-good "quad" effect, although the four recorded channels are intermingled to a considerable degree. Special decoder "logic" circuits can greatly enhance the separation of matrixed four-channel recordings, and anyone with a serious interest in quadraphony should invest in a good logic decoder. These are available as addon accessories and are built into a few four-channel receivers and amplifiers. You should be aware that most four-channel receivers claiming SQ capability do not have logic enhancement and cannot be expected to give a definite sense of channel separation.

The other major quadraphonic disc system is the CD-4 "compatible discrete" system developed by Victor Company of Japan. The majority of CD-4 records in this country are issued by RCA Victor, but other labels are joining them as the system becomes more widespread.

Unlike matrix records, which can be played by any stereo phono cartridge and can be transmitted over FM radio, the CD-4 system requires a special cartridge, with a frequency response extending to 45 kHz, and a separate decoder. It cannot be broadcast in 4-channel form. On the other hand, the CD-4 system has superior four-channel separation, producing a distinctly different overall effect than matrixed records, even when they are played through a full logic decoder.

Fortunately, all quadraphonic records, whether SQ, QS, or CD-4, can be played as stereo discs, without loss of content and with full fidelity. In this sense, they are compatible - but with stereo reproduction rather than with each other.

If you are planning a complete four-channel system, or intend to make a major changeover from an older stereo system, a receiver is the most logical choice for the central component. The better four-channel receivers have adequate power (25 to 50 watts per channel) for most purposes, and many of them have decoding facilities for all types of four-channel records.

However, no single receiver or decoding accessory gives optimum performance with all three record types. Each favors one of the systems, to the detriment of the others. In every case, however, an external SQ or CD-4 accessory can provide full flexibility and performance for the least favored system. Another point to watch for is the very low audio power ratings of some lower priced four-channel receivers. Often able to deliver between 7 and 10 watts per channel, these may not be suitable for driving many popular low-efficiency speakers except in a very small room.

It is easy to convert a stereo system to four channels, without any obsolescence. Connect a good full-logic SQ decoder, or a CD-4 demodulator, to the amplifier's tape recording outputs. The decoder front channels return to the tape monitoring inputs and the rear channels go to a second stereo amplifier which drives the rear speakers. The decoder acts as a system control unit and master volume control and its tape outputs, in turn, can be used for a different type of four-channel decoder, or for a tape deck.

If your system is to include the CD-4 system, check to see that your record player tonearm has low capacitance wiring, a necessity for most of the new CD-4 cartridges if their high-frequency response is to be maintained. Check with the manufacturers of the cartridge and the record player if you have doubts. If you simply install a CD-4 cartridge in your old record player, you may be disappointed in the results.

There are no hard and fast rules on speaker choice or placement for quadraphonic listening. As with stereo, the better the speaker, the better the sound. It is not necessary to have identical speakers for all channels, but they should have roughly similar sound qualities. Often it is possible to use smaller speakers in the rear channels (from the same manufacturer as your front speakers), with completely satisfactory results.

As for speaker placement, in most cases existing architecture or furnishings will prevent setting the rear speakers in the corners of the basic quadraphonic rectangle. This rarely impairs their effectiveness, but some experimentation is usually necessary for best results.

There are several four-channel headphones on the market. Although they do not sound like stereo phones (on four-channel material), they do not in the least simulate the effect of four-channel speaker listening. But, neither do stereo phones sound like stereo speakers!

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