The Experiment That Saved Hi-Fi

By the time World War II ended in 1945, the wartime shortage of home radio and phonograph products had become acute. Even radio experimenters were hampered by the shortage of parts, but that didn't stop some of them from tinkering with a concept they called "high fidelity". What would have stopped them cold didn't happen until a month after the war ended.
That was a report by Chinn and Eisenberg in the Proceedings of the IEE, describing the results of a study to investagate the tonal spectrum preference of radio listeners. An audience had been given a choice of three frequency ranges to choice from; narrow (150 - 3500 HZ), medium (100 - 5000 HZ), and wide (50 -10,000 HZ). Surprisingly, most of the listeners chose the narrow-range sound even after they were told it was "low fidelity".
Professional musicians listening to classical music picked the low-fi sound by an even greater margin then the average listener. Among the musicians , 73% chose narrow range while only 5% liked the wide range and 22% were undecided.
For Hi-Fi fans, that report was a double whammy. The study purported to fix the "ideal" frequency range for the recording and broadcasting industries. What good was it to build wide-range hi-fi amplifiers and speaker systems if the frequency response of records and radio broadcasts were to be restricted?
However, there wasn't much to be criticized in the experiment. The qualifications of the investigators were impeccable. One, a consultant to the office of Scientific Research and Development, with extensive experience in broadcasting, had been associated with M.I.T. and Harvard. His colleague was a professor of psychology. Their audio equipment was the best available - flat from 40 to 10,000 Hz with "supposedly" low measurable distortion. The speaker system used was coaxial with a multi-cellular horn for highs; folded horn for lows.

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.

Behind the filter, a small orchestra - piano, trumpet, violin, clarinet, contrabass, drums, and traps - was assembled. A sound-transparent curtain prevented the audience from seeing the position of the filter.Then Olson assembled his listners; chemists, and gardeners, doctors and farmers, secretaries and electricians - anyone who was available as worker or visitor at RCA laboratories. The orchestra played and A - B tests were made, the filter changed every 15 seconds during each number. For different tests, the letters A and B were reversed to prevent the results from being skewed by letter preference. The listeners made their choice, and added comments if they desired.
The results of the experiment produced a reversal of all previous studies. It was a striking victory for the concept of high fidelity. A strong majority, 69% of the listeners, preferred full-frequency-range hi-fi, compared to 31% who voted for the low-fi music.
But there was a suspicion that even some of the minority who didn't like the full-frequency range may have been reacting to something other than sound quality. Because of the small room, Olson could not supply classical music devotees with a full symphony orchestra. Some of them added negative remarks about popular music to their votes for narrow-range sound.
Olsen also disproved another belief held by the broadcasting industry; that the product of the upper and lower limits of the reproduced frequency range should always equal about 500,000 in order to insure proper balance between highs and lows. He found that his listeners did not approve when he cut off the bass at 100 Hz to balance the high-frequency cut-off at 5000 Hz.
Tests on speech produced comments that the restricted frequency range produced "muffled" speech that was not as intelligible as the full-range speech.
Olson's experiment showed that previous workers who had attempted to find the "ideal" frequency range for music reproduction had been working in the dark. Evidently his third suggestion, that distortion was less objectionable with a narrow-frequency range, was correct.

Get the Distortion Out.
"Distortion was inherent in the phonographs and radio receivers of that day." Dr. Olson said recently. "The engineers cut back the frequency range until the performance was satisfactory."
But the fact that the listeners preferred full-range sound, if undistorted, had now been proved. It gave a solid foundation for hi-fi development work that had once been conducted on faith only. The hi-fi or stereo fan of today owes much to Dr. Olson and to the men who kept building better amplifiers and speaker systems when no one else seemed to care enough to listen.
If you ever find that your ears and your test equipment disagree, trust your ears until they are proven to be wrong. The listeners who chose the narrow range for reproduced music were reacting to the high-order distortion in the wide-range equipment of the 1940's. In that respect their low-fi choice was the correct one and explains why the professional musicians objected more than the average listener to the distortion. And it was the ears of Dr. Olson's listeners that proved the desirability of a full-frequency range.
Perhaps there should be a minority report from the people who chose the narrow band with live music. One such reaction came from a lady in Texas when the local radio-TV shop returned a repaired console radio to her. "Oh good," she said. "I'll be glad to listen to a radio with good tone again. And the records you get today just don't sound like the old ones."
Maybe she read that 1945 report. Too bad she didn't catch Dr. Olson's experiment.