High fidelity or
hi-fi reproduction is a term used by home stereo listeners and
home audio enthusiasts (
audiophiles) to refer to high-quality
reproduction of sound or
images that are very faithful to the original performance. Ideally, high-fidelity equipment has minimal amounts of
noise and
distortion and an accurate
frequency response as set out in 1973 by the German
Deutsches Institut für Normung (DIN) standard
DIN 45500. This standard was well intentioned, but only mildly successful in defining 'high-fidelity'. DIN 45 500 approval provided audio equipment buyers with reassurance that their equipment was capable of good quality reproduction. In theory, only stereo equipment that met the standard could bear the words 'hi-fi', but in practice, the term was widely misapplied to audio products that did not remotely approach the DIN basis specifications.
By the 1990s, the term hi-fi for expensive high-quality home-audio electronics was largely replaced with
high-end audio.
History
The
1920s saw the introduction of
electronic amplification,
microphones, and the application of quantitative engineering principles to the reproduction of sound. Much of the pioneering work was done at
Bell Laboratories and commercialized by
Western Electric.
Acoustically-recorded
disc records with capriciously peaky
frequency response were replaced with electrically recorded records. The
Victor Orthophonic
phonograph, although purely acoustic, was created by engineers who applied
waveguide technology to the design of the interior folded horn to produce a smooth frequency response which complemented and equalled that of the electrically recorded Victor Orthophonic records.
Meanwhile, the rise of
radio meant increased popularity for
loudspeakers and
tube amplifiers, so there was a period of time during which radio
receivers commonly used loudspeakers and electronic amplifiers to produce sound, while phonographs were still commonly purely mechanical and acoustic. Later, electronic phonographs became available, as stand-alone units or designed to play through consumer's radios. The now ubiquitous
RCA connector was first introduced by the
Radio Corporation of America for this purpose.
The development of
Sound film in the 1930s led motion picture companies to develop amplification and loudspeaker systems to fill movie theaters with good quality sound at a reasonable volume. To achieve this result, they employed loudspeakers with separate sections for low and high frequencies ("
woofers" and "
tweeters"), connected via an
audio crossover network, and more carefully engineered
enclosures. This development exposed the public to better fidelity than home equipment was capable of at the time. Some movie stars purchased movie theater sound equipment for use in their homes but the cost and size put them out of reach for anyone of modest means.
After
World War II, several innovations created the conditions for a major improvement of home-audio quality:
- FM radio, with wider audio bandwidth and less susceptibility to signal interference and fading than AM radio, though AM could be heard at longer distances at night.
- Better amplifier designs, with more attention to frequency response and much higher power output capability, allowing audio peaks to be reproduced without distortion.
In the 1950s, the term
high fidelity began to be used by audio manufacturers as a marketing term to describe records and equipment which were intended to provide faithful sound reproduction. While some consumers simply interpreted
high fidelity as fancy and expensive equipment, many found the difference in quality between "hi-fi" and the then standard AM radios and 78 RPM records readily apparent and bought 33 LPs, such as RCA's New Orthophonics and London's ffrrs, and high-fidelity phonographs. Audiophiles paid attention to technical characteristics and bought individual components, such as separate turntables, radio tuners,
preamplifiers, power amplifiers and loudspeakers. Some enthusiasts assembled their own loudspeaker systems. In the 1950s,
hi-fi became a generic term, to some extent displacing
phonograph and
record player.
In the late 1950s and early 1960s, the development of the Westrex single-groove
stereophonic record led to the next wave of home-audio improvement, and in common parlance,
stereo displaced
hi-fi. Records were now played on
a stereo. In the world of the audiophile, however,
high fidelity continued and continues to refer to the goal of highly-accurate sound reproduction and to the technological resources available for approaching that goal. This period is most widely regarded as "The Golden Age of Hi-Fi", when tube equipment manufacturers of the time produced many models considered endearing by modern audiophiles, and just before solid state equipment was introduced to the market, subsequently replacing tube equipment as mainstream.
A very popular type of system for reproducing music from the 1970s onwards was the integrated
music centre which combined phonograph, radio tuner, tape player, preamp and power amplifier in one package, often sold with its own separate, detachable or integrated speakers. These systems advertised their simplicity; the consumer did not have to select and assemble the individual components. Purists generally avoid referring to these systems as high fidelity, though some are capable of very good quality sound reproduction.
Ascertaining high fidelity: double-blind tests
In a
double-blind experiment, neither the individuals nor the researchers know who belongs to the control group and the experimental group. Only after all the data has been recorded (and in some cases, analyzed) do the researchers learn which individuals are which. A commonly-used variant of this test is the
ABX test. This involves comparing two known audio sources (A and B) with either one of these when it has been randomly selected (X). There is no way to prove that a certain lossy methodology is
transparent. To scientifically prove that a lossy method is
not transparent, double-blind tests may be useful.
Semblance of realism
When high fidelity was limited to
monophonic sound reproduction, a realistic approximation to what the listener would experience in a
concert hall was limited. The general clarity of the sound, however, was not any less than with stereophonic sound reproduction. Researchers quickly realized that the ideal way to experience music played back on audio equipment was through multiple transmission channels, but the
technology was not available at that time. It was, for example, discovered that a realistic representation of the separation between performers in an
orchestra from an ideal listening position in the concert hall would require at least three loudspeakers for the front channels. For the reproduction of the
reverberation, at least two loudspeakers placed behind or to the sides of the listener were required.
Stereophonic sound provided a partial solution to the problem of creating some semblance of the
illusion of performers performing in an orchestra by creating a phantom middle channel when the listener sits exactly in the middle of the two front loudspeakers. When the listener moves slightly to the side, however, this phantom channel disappears or is greatly reduced. An attempt to provide for the reproduction of the reverberation was tried in the 1970s through
quadraphonic sound but, again, the technology at that time was insufficient for the task.
Consumers did not want to pay the additional costs required in
money and space for the marginal improvements in realism. With the rise in popularity of
home theatre, however, multi-channel playback systems became affordable, and many consumers were willing to tolerate the six to eight channels required in a home theater. The advances made in
signal processors to synthesize an approximation of a good concert hall can now provide a somewhat more realistic illusion of listening in a concert hall.
In addition to spatial realism, the playback of
music must be subjectively free from noise to achieve realism. The
compact disc (CD) provides about 90
decibels of
dynamic range,
which is about as much as most people can tolerate in an average
living room.
Audio equipment must be able to reproduce frequencies high enough and low enough to be realistic. The human hearing range, for healthy young persons, is 20 Hz to 20,000 Hz.
Most adults can't hear higher than 15 kHz.
CDs are capable of reproducing frequencies as low as 10 Hz and as high as 22.05 kHz, making them adequate, in range, to reproduce the frequencies that most people can hear.
The equipment must also provide no noticeable distortion of the
signal or emphasis or de-emphasis of any frequency in this frequency range. Except for spatial realism, good modern equipment can easily satisfy all of these requirements at a relatively moderate cost.
Modularity
Integrated,
midi, or
lifestyle systems, also known as
music centres, contain one or more sources such as a
CD player, a
tuner, or a
cassette deck together with a
preamplifier and a
power amplifier in one box. (
Midi has no connection with
MIDI technology in electronic instruments.) Such products are generally disparaged by
audiophiles, although some
high-end manufacturers do produce integrated systems. The traditional hi-fi enthusiast, however, will build a system from
separates, often with each item from a different manufacturer specialising in a particular component. This provides the most flexibility for piece-by-piece upgrades.
For slightly less flexibility in
upgrades, a
preamplifier and a power
amplifier in one box is called an
integrated amplifier; with a tuner, it is a
receiver. A monophonic power amplifier, which is called a
monoblock, is often used for powering a
subwoofer. Other modules in the system may include components like
cartridges,
tonearms,
turntables,
Digital Media Players,
digital audio players,
DVD players that play a wide variety of discs including
CDs,
CD recorders,
MiniDisc recorders, hi-fi
videocassette recorders (VCRs) and
reel-to-reel tape recorders. Signal modification equipment can include
equalizers and
signal processors.
This modularity allows the enthusiast to spend as little or as much as he wants on a component that suits his specific needs. In a system built from separates, sometimes a failure on one component still allows partial use of the rest of the system. A repair of an integrated system, though, means complete lack of use of the system.
Another advantage of modularity is the ability to spend one's money on only a few core components at first and then later add additional components to one's system. Because of all these advantages to the modular way of building a high-fidelity system instead of buying an integrated system, audiophiles almost always assemble their system from separates. Some of the disadvantages of this approach are increased cost, complexity, and space required for the components.
Modern equipment
Modern hi-fi equipment can include signal sources such as
digital audio tape (DAT),
digital audio broadcasting (DAB) or
HD Radio tuners. Some modern hi-fi equipment can be digitally connected using
fibre optic TOSLINK cables,
universal serial bus (USB) ports (including one to play digital audio files), or
WiFi support.
Another modern component is the
music server consisting of one or more
computer hard drives that hold music in the form of
computer files. When the music is stored in an
audio file format that is
lossless such as
FLAC,
Monkey's Audio or
WMA Lossless, the computer playback of recorded audio can serve as an audiophile-quality source for a hi-fi system.
See also
