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The investigators had kept record noise to a negligible level by using original master recordings and playing each one only
one time. To double check the results with records, a live network broadcast of a 29-piece orchestra with a 14-voice female
chorus was monitored in the listening room for some of the tests. Again, the frequency range for the medium and narrow
bands was altered by an electronic (single-section band-pass) filter inserted in the system. And the listeners liked the filter.
Highs Are for the Birds
If the study threw a wet blanket over hi-fi, it wasn't the first one. In 1944,O.J. Hanson,
chief engineer for one of the major broadcasting networks, questioned the desirability of high fidelity. He suggested that frequencies
above 10,000 Hz were good only for sound effects: non-musical noises such as key jingling, hand-clapping, and
resin squeaks. Anyway, he said, the jokes of a favoriate comedian were just as funny when heard on a radio with with a
200-to-3000Hz range as on a wide-range system.
Those who argued against a wide response on the grounds that it was impractical had many reasons to cite. They said that
a listener would have to sit directly in front of his speaker because if he were 45 degrees off the axis, the response would be
inadequate at frequencies as low as 3000Hz. Critics also noted that background noise increased along with bandwidth and that
the extension of high-frequency response beyond 5000Hz on AM radios would only result in "monkey chatter" due to the
10-KHz spacing of radio stations.
Such were the views of the "establishment" . It was hardly surprising, then, that many of the first post-WWII radio receivers
were built on the same chassis layouts as the last prewar models. The economic climate of wartime price fixing and high demand
was also partly to blame. But a scientific study which showed a one-sided preference for low-fi music discouraged all but the
most adventurous manufacturers.
Low-Fi Reigns Supreme.
And so the console AM radio was still king of the mountain, or at least of the American
living room. Eighteen million had been manufactured; the latest of them being superhets with a pair of push-pull pentodes
in the output stage. The power output may have been listed in the tube manual at 8 to 10 watts; but it was usually
considerably less than that, depending on how much distortion one would tolerate. A small output transformer coupled
the output tubes to a 10 or 12 inch electromagnetic stiff-coned speaker, mounted in the lower section of the open-backed
cabinet. That arrangement produced a booming resonance in the 200Hz region that almost masked the absense of
fundamental bass response under about 100Hz. The almost total lack of either electrical or mechanical damping on the
speaker permitted the cone to vibrate after a signal had ended and added the word "hangover" to our audio vocabulary.
Sometimes the radio amplifier was fed by a 78-r/min record player whose massive tone arm carried a crystal pick-up. At the
end of the cartridge was a "chuck" or set screw that held the stylus, which was called a needle but looked like a brad nail.
People who were fussy about record wear could substitute a cactus needle, which killed what little high-frequency response
might have escaped the other equipment.
Those were the "components" of a home music system; commercial sound systems were not much better. An investigation by
Eagleson and Eagleson in 1946 showed that, when listeners tried to musical instruments heard over a p.a. system, the results
were wild guesses. In a test involving 35 listeners, 22 of them musicians, the one who got the best score identified the
instrument correctly less than 40% of the time. And he wasn't one of the musicians. In fact, he'd had no musical training at all.
The Chinn-Eisenburg study clearly backed up the engineers who had argued for a "sensible" frequency range, and against
hi-fi. But when the paper was read carefully, some odd comparisons emerged. For example, when the professional musicians
listened to male speech, they showed a preference for widerange reproduction. Another curiosity: Why did listeners prefer
a higher sound intensity for speech than for music? This was a suspicious reversal of the normal difference in sound
intensity for live speech and live music.
Fortunately for the future of hi-fi, some readers were skeptical of the results. One of these was Harry F. Olson. Born in
Mt. Pleasant, Iowa, Olson had received his Ph. D at the University of Iowa in 1928 and had gone to work for RCA that year.
Six years later he was placed in charge of acoustical research for RCA.
As Olson analyzed the conclusions of the controversial paper, he decided that there could be three possible explanations
for the results. The first two were: People were so conditioned to a narrow frequency range from listening to the radio that
they accepted it as nautral. Musical instruments are improperly designed. They should be redesigned to eliminate the
undesirable overtones.
Olsen was offering these suggestions to cover all the possibilities. He knew that the professional musicians should have had
no difficulty choosing what was the most natural sound. And as for recognizing musical instruments, stripping the
overtones would rob each instrument of its individuality. A violin, for example, would lose its gutty string tone and sound
somewhat like a flute. One might as well write music for a battery of sine-wave generators!
The third possibility? Olson said, "the distortions and deviations from true reproduction of the original sound are less
objectionable with a restricted frequency range."
But how could he prove his suspicion? If distortion were the demon, his problem was to design an experiment that
would eliminate distortion. His solution was simple.
If distortion in amplifiers and speakers could not be eliminated, he would bypass 1945 electronics and use live music.
This time "live music" would mean exactly that - no microphone, no amplifier, and no speaker system.
A Real Acoustical Filter.
Olson's background in acoustics served him and the cause of high fidelity well. He
and John Preston, a member of the technical staff at RCA Laboratories, designed an acoustical filter to place between
a live orchestra and an audience. The filter was made by properly spacing 3 sheets of perforated metal. The holes in the
metal sheets provided a reactance (or inertance) to the vibrating air particles that increased with the frequency of
vibration. The trapped air volumes in the two sections of the filters, on the other hand, provided a reactance that
decreased with frequency, tending to absorb the vibration of the particles. By careful choice of hole size in the metal
sheets and air volumes (by spacing the sheets), Olson was able to obtain a cutoff at the desired frequency. He selected
the cutoff point to correspond to the high-frequency response of "very good" radios and phonographs of that time.
The cutoff point was 4000 Hz; however, as defined by radio and phonograph terminology, the filter was called a 5000-Hz
low pass filter.
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