March 1955 Popular Electronics
of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged.
are lots of audiophiles in the RF Cafe audience who might appreciate
this article on the characteristics of human hearing and ways in which
stereo hi-fi equipment attempts to reproduce realistic sound, as if
from a live performance. A handy-dandy chart is provided that shows
the characteristics of various audible frequency ranges, and the kinds
of speakers best suited for reproducing the sound. It was published
in 1955, but still should be applicable today.
See all articles
The audio frequency spectrum and its importance in hi-fi.
good approach to high fidelity is to determine what it is that hi-fi
enables us to hear. This analysis serves not only to explain the nature
of sound, but may well act as a yardstick for evaluating a hi-fi system.
All areas within the audio spectrum are important for satisfactory
reproduction of sound, particularly music. Even those very high regions
above 10,000 cycles contribute to listening pleasure, as this discussion
and the chart opposite show.
Most of us begin responding to
frequencies as low as 16 cps. This is more of a "feeling" point than
an actual hearing level. Music does not go down that far. The lowest
note on the piano keyboard is 27.5 cycles. The lowest fundamental tones
of large organs may go down to 20 cycles, and the little known octa-contra
bass clarinet is reputed to hit that low. You can get an idea of the
kind of deep, overwhelming power suggested by these "sub-basement" lows
if you recall the lowest rumble of thunder you've ever heard.
music, however, occurs above 32 cycles. The second and third octaves
(32 to 128 cycles) are the regions of most bass notes, the all-important
The fourth and fifth octaves (128 to 512 cycles)
include the relatively higher bass tones such as those produced by tympani
and the higher strings of the bass viol. The fundamental tones of most
horns, as well as of the male voice, appear in this area.
sixth and seventh octave region, while above "middle C" on the piano,
and musically in the treble range, is often termed "mid-range" from
the point of view of its coverage by reproducing equipment. This is
the frequency area easiest to reproduce. It includes the minimum range
needed for voice communication, but without the bass notes below and
the overtones above it, a "pinched" quality - like that of a voice on
telephone - results. The trumpet's tones extend into this range, as
well as those of the female voice. At the upper reaches of this range
are the notes of the flute. The fundamental tones of most musical instruments
are to be found between the fourth and seventh octaves.
brilliance of clashing cymbals and the piping of the piccolo bring us
into the region above 2000 cycles. Violin notes can be heard in this
area to well over 3000 cps. The highest piano note, or top of the 8th
octave, reaches 4186 cps. Certain speech and musical sounds, of a labial
and fricative nature, reach into the 9th octave. Many important overtones,
or harmonics generated by fundamental tones originating in lower octaves,
are sounded in the 9th. Our ability to hear these overtones helps us,
to a large degree, to distinguish between different instruments. It
also creates the illusion of "presence" or reality in music reproduction.
These harmonics, or overtones, continue up to 16,000 cycles
and beyond. To hear them is to perceive the final touch in tonal brilliance
and the subtle shadings of instrumental timbre that characterize live
performances of music and the best hi-fi reproducing systems. To some
extent, this region of frequencies is an audio "no man's land" because
of the controversy regarding its importance in reproducing systems.
Some observers claim that we can fully enjoy music without the need
to catch anything above 12,000 cycles. Others point to the limitations
of present-day program sources, such as records and pickups which do
not go up to 16,000 cycles.
By far, the biggest single problem
in assembling a hi-fi system, as regards reproducing the full audio
spectrum, is the choice of a suitable loudspeaker and enclosure. Unfortunately,
no single speaker has yet been designed that covers the complete audio
spectrum. As shown on our chart, the "fi" can become truly "hi" only
witha speaker system which uses separate speaker units and correct frequency
dividing facilities. When you consider the number and variety of sizes
and shapes of instruments that produced the original sounds, you can
begin to appreciate why a greater variety of speakers will reproduce
them better than a single speaker. And, in any case, no decent bass
reproduction is possible without a suitable enclosure for the low frequency
February 3, 2014