The Cochineal: An Online Student Journal and Repository of Conservation, Preservation, and Cultural Studies

Author: Andrew D. Crews
Date: December 1, 2003
Class: 392L – Introduction to Audio Preservation and Reformatting
Instructor: Karl Miller

From Poulsen to Plastic: A Survey of Recordable Magnetic Media

*** Editor's Note: This paper uses footnotes which are only available in the pdf version***

In the early days of recorded sound, phonographic recordings reigned supreme. From Thomas Edison’s recorded cylinders to Berliner’s discs, the phonograph was the dominant medium of sound reproduction from its invention in 1877 until the mid-20th century. Unfortunately, recording phonographic discs and cylinders required a professional sound studio and hundreds, if not thousands, of dollars in recording and production equipment. Another drawback to these recordings was their fragility. Early shellac recordings were easily scratched and would shatter if dropped. While visiting Edison’s laboratory in early 1878, Oberlin Smith, owner and founder of the Ferracute Machine Company, observed yet another problem with mechanical recordings. While engraving the master, the friction of the needle adds noise to the recording. Smith sought to improve the recording process by eliminating this friction and recording magnetically upon a brass wire impregnated with steel dust. Oberlin experimented with his ideas for a while, but soon abandoned them due to business concerns. He published an article detailing his theories in hopes that a future entrepreneur would continue his work.

Valdemar Poulsen, a telephone technician in Copenhagen, Denmark invented the first functioning model in 1898. His Telegraphone, a magnetic recording apparatus to record telephone messages, recorded on thin wire that recorded a maximum of thirty seconds at a rate of seven feet per second. Despite winning the Grand Prix at the Paris Exposition in 1900, the Telegraphone was not a success. The original recording wire would twist, later requiring a change to steel tape as a recording medium. Even this was not sufficient for recording, as the dynamic range was a mere 20 decibels resulting in a high background noise level – inferior to engraved recordings. Marketing firms created to sell the Telegraphone in Denmark and the United States collapsed and faded into obscurity by 1916. Various firms conducted experiments in magnetic recording for the next thirty years, resulting in the Soundmirror, created in 1937 by the Brush Development Company, and the Mirrophone, developed by Bell Laboratories and displayed at the 1939 World’s Fair. Neither of these were commercially successful. The technology would not catch on for another ten years. During World War II, the Germans began experimenting with a magnetic tape created with a paper base coated with iron oxide. “The early German tapes used a type of oxide known as raven red, a term borrowed from the barn paint of the same name.” The Allied forces confiscated some of the German recording machines, called Magnetophones, and soon began licensing the rights to American firms to create similar versions. After the war, both Webster-Chicago and Sears & Roebuck began marketing wire recorders for home usage, while companies such as Ampex, Magnecord and Rangertone worked on improving the German technology. The Magnetophones recorded at a speed of 76 centimeters, or 30 inches, per second due to the limited frequency response of the 6.5 mm wide tape – which by this time was made of cellulose acetate. With improvements made to the magnetic oxide by the 3M Corporation, output increased by 12 dB over the original German tape. In addition, recording speed decreased from 30 inches per second (ips) to 15 ips, and later progressively halved to 7.5 ips, 3.75 ips, 1 7/8 ips and 15/16 ips. Another improvement permitting longer recording time was the introduction of progressively thinner tape. As tape gained higher fidelity sound reproduction along with greater capacity, reel tape recorders gradually replaced wire recorders for consumer use.

Still, tapes had numerous drawbacks. Recording equipment was still quite expensive and not affordable for the average consumer. Tapes were also more expensive, $12.50 for prerecorded music compared to $4 for an LP record. They required hand threading onto reels and could easily be unwound or misaligned during recording or playback, leading to damage. Manufacturers sought to find an enclosed reel format that was also user-friendly for playback and recording.

The Brush Development Company and the Armour Research Foundation had developed cassette-based wire recorders for use by the military during World War II. These were not commercially successful after the war, due to the rapid progress made by magnetic tape. RCA was the first to market what they called a “cartridge”, actually an early cassette format, during the late 1950’s.


The RCA cartridge was large, 7 _ inches by 5 inches by _-inch thick using _-inch tape at a selectable rate of 3.75 ips or 1 7/8 ips for total recording times of 30 or 60 minutes respectively. The tape had five openings along the bottom edge, two for capstans and three for heads. The heads could be oriented differently by recorder type. On some machines, recorded tracks could be selected with a switch labeled “A” or “B”, with the “A” side being stereo (or dual mono) tracks one and three, and “B” occupying tracks two and four. In essence, this was a four-track machine with all the tracks playing in the same direction. The tape was configured in such a way that it was also possible to record on each side of the tape with two tracks in each direction. Oddly, the player had no way to fast-forward the tape. It required flipping the tape over and rewinding it. The cartridge had a notch in the back of the case that held a spring-loaded brake. When the cartridge was not in the player, the brake kept the tape from unwinding from the reel. This feature was unique to the RCA format. Another interesting feature incorporated into the design was the use of flangeless reels for spooling the tape. The sides of the case served to keep the tape aligned. Despite being configured for home playback and recording, the RCA cartridge machines were not widely popular. The machines were too expensive for average consumers and contained built-in amplifiers and speakers that serious audiophiles did not want .

During this same time, CBS was experimenting with its own cartridge format, a self-threading reel that used a narrower 0.15-inch tape and ran at a slower 1 7/8 ips speed. It recorded in three-track stereo. Once inserted, the tape inside the cartridge would thread automatically onto a second reel permanently fixed inside the player. It, too, failed to catch on for the similar reasons: too expensive and unimpressive performance.


The self-threading reel cartridge

Early in the 1950’s Bernard Cousino developed an endless-loop cartridge for advertising purposes. The endless-loop was a length of tape, spliced together at the ends that pulled tape from the inner part of the reel, across the playback head and wound it back onto the outer part of the reel. His original Audiovendor cartridge required looping the tape around the heads of a traditional open-reel player. The first application in 1952 was to advertise a dairy company by playing messages inside a cow’s head. Later, Cousino created the Echomatic, a fully enclosed tape system. He licensed these cartridges to Orrtronics Corporation, who promoted them under the name “Tapette”, but they were primarily spoken word tapes, and not marketed for high-fidelity sound reproduction. Interestingly, Cousino would develop an 8-track cartridge format for high-fidelity use in the mid-1960’s. Although he had financial backing from the Champion Spark Plug Company and an arguably superior concept, his 8-track format was not accepted and never made it to the marketplace.


An example of a Tapette cartridge

Despite the limited scope of Cousino’s Tapette, he was able to inspire future entrepreneurs, such as George Eash, Earl Muntz and William Lear. Eash, who rented space in the same building as Cousino in the 1950’s, developed the Fidelipack cartridge format. The radio broadcasting industry quickly adopted Fidelipack “carts” for recording and playback of commercials and station jingles. The cartridges were generally three-tracks: left and right channels, plus a cue track containing tones to start and stop automated players. They used _” tape that recorded at a speed of 3.75 ips. Muntz, a California automobile distributor, first seized upon the idea of using the Fidelipack cartridges in car stereos. His Stereo-Pak revised the endless-loop cartridges by adding another track to make four, two programs of two stereo channels each. Total playing time was 40 minutes for the two-program system. The splice, creating the endless 20-minute loop, was made of foil. The playback mechanism would sense the end-of-tape marker and shift the two heads to the adjacent channels. The Muntz machines were the first to offer true stereo for automotive use, but their success was soon eclipsed by William Lear’s invention – the 8-track cartridge.

Lear, the inventor of the Learjet, became a distributor of the Muntz system in 1963 and installed the players in his jets. Like the original Fidelipack system, the Stereo-Pak cartridges were prone to jamming due to their complex design, so Lear began to redesign them. He doubled the number of tracks from four to eight on the same _” tape while using the same speed of 3.75 ips. The Stereo-Pak required a hole in the case facilitating insertion of the player’s pressure roller to advance the tape. The 8-track case incorporated the pressure roller inside the case itself, and reduced the number of moving parts.


The case was rather chunky with dimensions of 5.25” by 4” with a thickness of slightly less than 1”. As shown in the diagram, the capstan in the player pressed against the pressure roller transporting the tape along the playback head. The solenoid coil skimmed the surface of the tape until it sensed the foil splice to trigger the mechanism and move the heads to the next series of tracks. By doubling the number of tracks, the recording length doubled to 80 minutes. However, the fidelity decreased due to the halving of the available recording surface. Despite this, Lear was able to convince the Ford Motor Company to make the 8-track stereos available as an option on their 1966 automobile line. He had been a founder of the Motorola Corporation and Motorola supplied stereos to Ford. They were an unqualified success, selling 65,000 units that year. General Motors and Chrysler began offering the players in their cars the next year. “By the end of 1967, an estimated 2.4 million 8-track players were in use.” The 8-track suffered from some of the same drawbacks as the 4-track Stereo-Pak did: it was not possible to fast-forward nor rewind to specific points on the tape; the moving heads eventually went out of alignment causing “crosstalk”, or adjacent tracks playing concurrently; and the tape used by Lear was inferior. Since the Ampex Corporation had been a financial backer of his Learjet Company, their tape was the magnetic media chosen for the 8-track cartridges. Ampex tape was inferior to that produced by the German BASF Corporation. Due to the success of the 8-track car stereos, manufacturers began to offer 8-track players for home and portable use. Some manufacturers offered 8-track recorders, but they were not successful. The cartridge format was acceptable for playing pre-recorded music, but was “an inherently unstable design, subject to frequent mechanical problems, and missing the basic advantages of conventional tape machines: namely fast forward and reverse, easy erasure, editing and indexing” which impeded its use for home recording. Still, the 8-track dominated the market until the mid-1970s when its popularity waned due to the acceptance of the compact cassette.

Another 1960s cartridge format was the Playtape, introduced into the market in 1966 by Frank Stanton. Like the 4-track and 8-track, the Playtape was an endless loop format, but with only two tracks. Stanton developed the format, not for use as a car stereo, but as an affordable replacement for a transistor radio. Playtapes were produced for use in portable players marketed by Sears and MGM. Sears offered the more affordable model, at $19.95, and MGM the more upscale model with tone controls and a better speaker for $29.95. They were offered in five different lengths in color-coded cartridges.

  • Red – equivalent to a 45 rpm single
  • Black – equivalent to a 4-song e.p. record
  • Blue – children’s music
  • White – full album recording
  • Gray – spoken word and educational recordings

Playtape marketed itself successfully in the late 1960s by acquiring rights to distribute recordings by major artists, including the Beatles, the Animals, Frank Sinatra, Nat “King” Cole, and the complete Motown catalog. Despite the marketing success, the cartridges were low fidelity, non-recordable and only playable through cheaply made, portable units. Each cartridge could play two monaural tracks or one stereo track. Similar in construction to the 8-track cartridges, they also incorporated an internal pressure roller, but the case was much smaller – approximately 3” by 2 7/8” and 9/16” thick.


Relative size of Playtape and 8-track cartridges

Once the 8-track and 4-track formats moved from car to personal stereos, the Playtape was doomed. They offered higher fidelity equipment and greater versatility with the car stereo option. Volkswagen dealerships offered a Playtape car stereo as a dealer option in 1968, but it was too late. After 1971, the Playtape format disappeared from the market.

The compact cassette was by far the most successful of any magnetic tape product for home recording. Developed by the Dutch Philips Corporation in 1961, it combined features of both the RCA Playtape and CBS cartridge systems developed earlier. Like the RCA design, the tape wound around flangeless hubs inside the cassette case. The compact cassette also used the 0.15” tape and 1 7/8 ips speed of the CBS format. The case dimensions were a very small 4” by 2.5” by 11/32” thick. Philips engineers claimed that five considerations had driven the design of the compact cassette:
1. Smallest possible dimensions with a playing time of 30 minutes (per side).
2. Simple sturdy construction.
3. Reliability
4. Maximum tape protection
5. Low energy consumption during playback and rewind.



Philips did not initially design the compact cassette for high fidelity, stereo applications. It was marketed in America under the “Norelco” brand as a “rather sophisticated toy for the domestic consumer market.” Two factors limited the frequency response capabilities: the slow tape transport speed and the narrow width of the tape. In the late 1960’s, DuPont developed a chromium dioxide coating enabling greater frequency response, able to reproduce frequencies in the 15-20 KHz range. Memorex, BASF and Sony each licensed the technology from DuPont to produce chromium dioxide, or “high bias” cassettes.

Along with improved oxide coatings, manufacturers produced gradually thinner tapes to enable longer recording and playback times.
C60 tape – 18 _m thickness – 92 m length
C90 tape – 12 _m thickness – 133 m length
C120 tape – 9 _m thickness – 184 m length
Tape base thicknesses 12 _m, 8 _m and 6 _m respectively.

During the same period in the late 1960s/early 1970’s, “compander” (compressor/expander) noise reduction systems were developed to further increase the signal-to-noise ratio of the compact cassette. The Dolby B type noise reduction boosted the high frequencies by 10 dB during the recording process and attenuated them by 10 Db on playback, effectively increasing the signal-to-noise ratio by 10dB. The later Dolby C type increased the signal by 20 dB and the Dolby SR increased it by 24 dB. In the 1980s, a third type of cassette tape was marketed: the Metal tape. Rather than the standard ferric oxide (FeO3) or chromium dioxide (CrO2), the polyethylene teraphthalate (Mylar) base was coated with two different formulations. The MP tape was coated with iron particles and the ME tape “replaced the conventional particulate coating with a thin evaporated (vacuum-deposited) metal (cobalt-alloy) layer” providing greater response at higher frequencies. Because of the advancements in magnetic tape technology, the compact cassette replaced the 8-track as the preferred format for prerecorded music during the late 1970s and began to outsell the vinyl LP record during the mid-1980s. The compact disc, introduced in 1982, outsold the LP by 1988 and only took two more years to become more popular than the cassette, due to its random-access format and higher fidelity digital audio. In 1987, cassettes held 63% of the market for recorded music - by 2001, only 5%. Ironically, the compact cassette remains popular for its original intended function – spoken word recording. Cassettes hold more than CD’s (90 or 120 minutes vs. 74) and are more popular for audiobooks.

In 1976, the Sony Corporation hoped to replace the compact cassette with yet another design, this one similar to the original RCA cassette format. Sony called it the Elcaset, taken from L-cassette, or “large cassette”.


The Elcaset used _”, double the width of the compact cassette tape, and the faster 3.75 ips speed for better reproduction than the compact cassette. The Elcaset case was also designed differently. It was larger and more ruggedly designed: 5 7/8” (15cm) by 4” (10 cm) and 13/16” (2cm) thick. The playback mechanism pulled the tape out of the case for more precise tracking across the head, and some players had dual capstan/pressure rollers for greater tape stability. The case looked similar to the compact cassette case, except that it exposed the tape at the top of the case rather than the bottom. There were left and right covers to protect the tape when not in the machine. The Elcaset also contained a type of brake to prevent the hubs from inadvertently unwinding. The frequency response of the Elcaset is shown below compared to a compact cassette with similar tape formulation. The graph shows less rolloff of high frequencies over 10 KHz.

The Elcaset tape had two-channel stereo on each side, like the compact cassette, but also added two tracks for cueing information resulting in six total tracks. The machines were marketed mainly for discriminating audiophiles who would appreciate the improved fidelity over the compact cassette. JVC, Teac, Akai, Technics and Sony produced both home and portable units but they were too expensive ($600 - $1100) to compete with the already established, affordable cassette format. No prerecorded Elcaset tapes were ever produced and the machines were withdrawn from the market after only a couple of years.

Interestingly, when the Sony pulled the Elcaset from the market, they auctioned them off to a Finnish company. The company then sold them in Finland for bargain prices, roughly $175 to $300 US, where they became quite popular! Here is an interesting size comparison between the Elcaset, the compact cassette and the original RCA model.

The wide acceptance of the compact disc has diminished, but not eliminated, magnetic tape. The compact cassette has not become obsolete, as did the 8-track and other tape formats. 90% of all audiobooks are available on cassette, and millions of blank cassettes are sold each year. Ironically, it may be the compact disc that reaches obsolescence well before magnetic tape. While the cassette has captured a niche market, making it the preferred medium for spoken word recording, manufacturers are currently developing new technologies to replace the compact disc with better, higher resolution mediums for prerecorded music. One thing seems certain. There will never be a long-term standard format. Consumers must continue to migrate recordings from one format to another to keep up with rapidly changing technology and ever-shorter media lifecycles.

Bibliography
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Daniel, Eric D.; Mee, C. Dennis; Clark, Mark H. Magnetic Recording: The First 100 Years, (1999), The Institute of Electrical and Electronics Engineers, New York

“Digital Music: Fast-forwarding tapes to oblivion?” USA Today, November 23, 2001, <http://www.usatoday.com/tech/techreviews/2001/11/23/cassette-rip.htm>, (Accessed November 29, 2003)

“History of the 8-track Tape” <http://www.recording-history.org/HTML/8track5.htm> (Accessed November 15, 2003)

“Playtape” <http://mhintze.tripod.com/audio/playtape.htm> (Accessed November 15, 2003)

Sinclair, Ian R., Newnes Audio and Hi-Fi Handbook, (1993), Butterworth – Heinemann Ltd., Linacre House, Jordan Hill, Oxford

“The Dead Media Project” <http://www.deadmedia.org/notes/6/066.html>, (Accessed November 28, 2003)

“The end of the Elcaset”, <http://home.iae.nl/users/pb0aia/cm/elcaset/el-end.html>, (Accessed November 28, 2003)

“Web Generation – Eight-track history” <http://www.wgeneration.com/70f4.html> (Accessed November 14, 2003)

Westcott, Charles G.; Dubbe, Richard F., Tape Recorders – How They Work, (1974) Howard Sams & Co., Indiana

“William Lear” http://history.acusd.edu/gen/recording/lear.html (Accessed November 20, 2003)

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