Gramophone Record - Limitations - Sound Fidelity

Sound Fidelity

Overall sound fidelity of records produced acoustically using horns instead of microphones had a distant, hollow tone quality. Some voices and instruments recorded better than others; Enrico Caruso, a famous tenor, was one popular recording artist of the acoustic era that was well matched to the recording horn. It has been asked, "Did Caruso make the phonograph or did the phonograph make Caruso?"

Delicate sounds and fine overtones were mostly lost, because it took a lot of sound energy to vibrate the recording horn diaphragm and cutting mechanism. There were acoustic limitations due to mechanical resonances in both the recording and playback system. Some pictures of acoustic recording sessions show horns wrapped with tape to help mute these resonances. Even an acoustic recording played back electrically on modern equipment sounds like it was recorded through a horn, notwithstanding a reduction in distortion because of the modern playback. Toward the end of the acoustic era, there were many fine examples of recordings made with horns.

Electric recording which developed during the time that early radio was becoming popular (1925) benefited from the microphones and amplifiers used in radio studios. The early electric recordings were reminiscent tonally of acoustic recordings, except there was more recorded bass and treble as well as delicate sounds and overtones cut on the records. This was in spite of some carbon microphones used which had resonances that colored the recorded tone. The double button carbon microphone with stretched diaphragm was a marked improvement. Alternatively, the Wente style condenser microphone used with the Western Electric licensed recording method had a brilliant midrange and was prone to overloading from sibilants in speech, but it was generally better at picking up sounds more accurately than carbon microphones were.

It was not unusual, however, for electric recordings to be played back on acoustic phonographs. The Victor Orthophonic phonograph was a prime example where such playback was expected. In the Orthophonic, which benefited from telephone research, the mechanical pickup head was redesigned with lower resonance than the traditional mica type. Also, a folded horn with an exponential taper was constructed inside the cabinet to provide better impedance matching to the air. As a result, playback of an Orthophonic record sounded like it was coming from a radio.

Eventually, when it was more common for electric recordings to be played back electrically in the 1930s and 1940s, the overall tone was much like listening to a radio of the era. Magnetic pickups became more common and were better designed as time went on, making it possible to improve the damping of spurious resonances. Crystal pickups were also introduced as lower cost alternatives. The dynamic or moving coil microphone was introduced around 1930 and the velocity or ribbon microphone in 1932. Both of these high quality microphones became widespread in motion picture, radio, recording, and public address applications.

Over time, fidelity, dynamic and noise levels improved to the point that it was harder to tell the difference between a live performance in the studio and the recorded version. This was especially true after the invention of the variable reluctance magnetic pickup cartridge by General Electric in the 1940s when high quality cuts were played on well-designed audio systems. The Capehart radio/phonographs of the era with large diameter electrodynamic loudspeakers, though not ideal, demonstrated this quite well with "home recordings" readily available in the music stores for the public to buy.

There were important quality advances in recordings specifically made for radio broadcast. In the early 1930s Bell Telephone Laboratories and Western Electric announced the total reinvention of disc recording: the Western Electric Wide Range System, "The New Voice of Action." The intent of the new Western Electric system was to improve the overall quality of disc recording and playback. The recording speed was 33⅓ rpm, originally used in the Western Electric/ERPI movie audio disc system implemented in the early Warner Brothers' Vitaphone "talkies" of 1927.

The newly invented Western Electric moving coil or dynamic microphone was part of the Wide Range System. It had a flatter audio response than the old style Wente condenser type and didn't require electronics installed in the microphone housing. Signals fed to the cutting head were pre-emphasized in the treble region to help override noise in playback. Groove cuts in the vertical plane were employed rather than the usual lateral cuts. The chief advantage claimed was more grooves per inch which could be crowded together resulting in longer playback time. Additionally, the problem of inner groove distortion which plagued lateral cuts could be avoided with the vertical cut system. Wax masters were made by flowing heated wax over a hot metal disc thus avoiding the microscopic irregularities of cast blocks of wax and the necessity of planing and polishing.

Vinyl pressings were made with stampers from master cuts that were electroplated in vacuo by means of gold sputtering. Audio response was claimed out to 8,000 Hz, later 13,000 Hz, using light weight pickups employing jeweled styli. Amplifiers and cutters both using negative feedback were employed thereby improving the range of frequencies cut and lowering distortion levels. Radio transcription producers such as World Broadcasting System and Associated Music Publishers (AMP) were the dominant licensees of the Western Electric wide range system and towards the end of the 1930s were responsible for two-thirds of the total radio transcription business. These recordings use a bass turnover of 300 Hz and a 10,000 Hz rolloff of −8.5 dB.

Developmentally, much of the technology of the long playing record, successfully released by Columbia in 1948, came from wide range radio transcription practices. The use of vinyl pressings, increased length of programming, and general improvement in audio quality over 78 rpm records were the major selling points.

The complete technical disclosure of the Columbia LP by Peter C. Goldmark, Rene' Snepvangers and William S. Bachman in 1949 made it possible for a great variety of record companies to get into the business of making long playing records. The business grew quickly and interest spread in high fidelity sound and the do-it-yourself market for pickups, turntables, amplifier kits, loudspeaker enclosure plans, and AM/FM radio tuners. The LP record for longer works, 45 rpm for pop music, and FM radio became high fidelity program sources in demand. Radio listeners heard recordings broadcast and this in turn generated more record sales. The industry flourished.