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
“audiotools.com – Vintage Recording Formats” <http://audiotools.com/oldf.html#8t>
(accessed November 18, 2003)
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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