The audio recording: a minimal history (part two)

Electric period (1925 – 1945)

After the end of World War I, record companies began to face their first opponent: radio. By the early 1920s this medium had become very popular, and the quality of sound obtained through microphone and loudspeaker was far superior to that of mechanical gramophone recording. This difference did not escape the attention of companies that had begun experimenting with recording systems based on microphones-a newly invented device-in place of the horn (HMV had an experimental system up and running in 1924). The second period of the story we are telling opens in this context with the introduction of the integrated system of the Western Electric consisting of electric microphones, electronic signal amplifiers, and electromechanical recorders; this system was quickly adopted by the major U.S. record labels beginning in 1925, while several variants were made in Europe essentially aimed at avoiding payment of the onerous Royalties that the American manufacturer required.

Maxfield and Harrison were two engineers from Bell Telephone Laboratories who had been commissioned to develop high-quality public event amplification systems in the 1920s. Achieving this goal implied large output powers over a wide frequency range and at the same time low distortion. The know-how acquired in the course of the work enabled them to approach the topic of registration with knowledge never previously applied to that topic. For the first time, all elements of recording, from the source to the machine on which the record was to be played, were the subject of scientific research. The result was the Western Electric (sometimes Westrex (Fig. 6)) recording system.

The realization of the W.E. system was made possible by the introduction, in the preceding years, of certain technologies among which we should certainly mention the first vacuum tube (or thermionic valve), i.e. the triode by A. Fleming; this is an electronic amplification device still produced and in use today. Another important invention, which contributed to the improvement of sound reproduction, was the construction in 1911 of the first moving-coil loudspeaker, the Magnavox Loudspeaker,

at the hands of Edwin Pridham and Peter Jensen, whose first public demonstration took place on December 10, 1915 at Golden Gate Park in San Francisco. Related to this invention, it is interesting to note that its operating principle-essentially a reverse microphone-has remained conceptually unchanged to the present day, although incorporating improvements in construction materials. What in the original loudspeaker was a cone made of pleated paper in order to improve its rigidity is now a cone made of carbon fiber or ceramic; the “motor” of the loudspeaker, i.e., the magnetic assembly, has also evolved using sophisticated materials such as neodymium; however, the general principle remains the same.

Despite the name, in the electric period, sound recording was a technologically hybrid process: sound was captured, amplified, filtered and balanced electronically, and the record cutting head was also electrically powered. There remained, however, a conspicuous mechanics-based portion in the process: the signal was still physically transcribed into a wax “master” disk. In addition, discs for end users were mass-produced by a mechanical process using a metal mold, obtained by electro-forming from the wax master, employing a suitable substance for the purpose, first a shellac-based compound, then polyvinyl plastic.

The results obtained with the Westrex system made acoustic recording obsolete. For the first time it was possible to accurately record an entire orchestra. Now the gramophone could rival the radio. Within weeks, Victor and Columbia in the United States and HMV and British Columbia converted to the new process. Early electric recordings were mainly of popular music, but soon followed classical when once he understood the specific needs of that genre.

Among the merits to be attributed to the Western Electric system is certainly the significant improvement in the fidelity of sound recording, having increased the range of reproducible frequencies (between 60 Hz and 6,000 Hz) and, most importantly, allowing the sound engineers – professional figure that emerged at this time–to capture a wider spatial image and harmonically richer, more detailed and balanced sound, partly through the simultaneous use of multiple microphones connected to multi-channel electronic amplifiers (Multichannel), compressors, filters and mixers. In addition, the development of electronic amplifiers for musical instruments allowed instruments with less powerful output, such as the guitar and double bass, to be able to be recorded alongside brass and other instruments naturally more gifted in this regard.