The 8-track cartridge is a now-obsolete audio storage magnetic tape cartridge technology, popular during the 1960s and 1970s. The 8-track was created by Bill Lear at Lear Inc. (the company of Lear Jet fame), after Bill Lear took a ride with Earl "Madman" Muntz, who had rigged up a cruder 4-track stereo tape system in his car.
The original format for magnetic tape sound reproduction was reel-to-reel audio tape recording, first made available in the 1940s. However, the machines were bulky, and the reels themselves were more difficult to handle than vinyl records. Born from the desire to have an easier to use tape format, the enclosed reel mechanism was introduced in the mid 1950s.
The cartridge was designed in 1956 around a single reel with the two ends of the plastic recording tape joined with a piece of conductive foil tape to make one continuous loop. A motorized capstan in the player rolled against a pinch wheel inside the cartridge to pull the tape across the player's read head. The tape was pulled from the inside of the reel, passed across the opening at the end of the cartridge and wound back onto the outside of the same reel. Because the tape had to continuously slip in an ever-tightening circle as it traversed the reel, it had to be coated with a very slippery backing material, such as graphite. This coating worked against the friction drive of the capstan and pinch-wheel, leading to poor speed control of the tape (wow and flutter). This made the format less popular with audiophiles. Note that the reel itself is passive - it is not driven, but is pulled around by the tape being drawn from the centre. Since the outside edge is of greater diameter, it is moving faster, and this speed difference holds the tape in tension. While this arrangement is extremely simple, allowing very simple and cheap players to be designed, unlike a two-reel system it doesn't permit winding of the tape either way. Some players allowed a limited fast-forward by simply speeding up the motor while cutting off the audio, but rewinding was impossible.
The original cartridge format had four monaural or two pairs of stereo tracks. When the foil tape passed across a pair of contacts close to the read head, it signaled the player to switch to the next program track (achieved by physically moving the head up and down mechanically in most cases), allowing the cartridge to play continuously with no rewinding, though there was usually a short gap in the music at the join in the tape. The playing time was later doubled by recording four stereo tracks on the tape, although this made each track half as wide, reducing the sound quality. This design was dubbed "8-track" to distinguish it from the original format, which then became a "4-track cartridge" by back-formation.
The popularity of both 4-track and 8-track cartridges grew from the booming automobile industry. In 1965, Ford Motor Company introduced built-in 8-track players as a custom option. By 1966, all of their vehicles offered this upgrade. Thanks to Ford's backing, the 8-track format eventually won out over the 4-track format.
Despite mediocre audio quality and the problems of fitting a standard vinyl LP album onto a four-program cartridge, the format gained steady popularity due to its convenience and portability. Home players were introduced in 1967. With the availability of cartridge systems for the home, consumers started thinking of 8-tracks as a viable alternative to vinyl records, not just as an automobile convenience. Within the year, prerecorded releases on 8-track began to come along at nearly the same time as the vinyl releases.
The devices were especially popular among professional truck drivers as this was the first successful prerecorded playback device for use in a moving vehicle. Earlier attempts to apply mechanical disk players were troubled by skipping induced by vehicle motion.
However, another format was just beginning to appear: the compact audio cassette, less than half the size of the 8-track cartridge. The 8-track cartridge had merely set the stage for the handier, recordable cassette.
8-track players still remained a common feature in homes and automobiles until the early 1980s, slowly fading into obscurity. By the time the compact disc arrived in the late 1980s, the 8-track had all but vanished, found mostly among collectors. The 4-track cartridge was also still used at some radio stations.
The center extraction tape concept continues to be used in modern cinema movie projectors, although in that application the spool is actively rotated, and not drawn by tension on the film.
- 8-track history (http://www.8trackheaven.com/)
- Collecting 8-tracks (http://dmoz.org/Arts/Music/Collecting/8-track/)