The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a magnetic tape sound recording format. Although originally designed for dictation, improvements in fidelity led the Compact Cassette to supplant reel-to-reel tape recording in most non-professional applications. Its uses ranged from portable audio to home recording to data storage for early microcomputers. Between the early 1970s and late 1990s, the cassette was one of the two most common formats for prerecorded music, first alongside the LP and later the Compact Disc. The word cassette is a French word meaning "little box."
Compact Cassettes consist of two miniature spools, between which a magnetically coated plastic tape is passed and wound. These spools and their attendant parts are held inside a protective plastic shell. Two stereo pairs of tracks (four total) or two monaural audio tracks are available on the tape; one stereo pair or one monophonic track is played or recorded when the tape is moving in one direction and the second pair when moving in the other direction. This reversal is achieved either by manually flipping the cassette or by having the machine itself change the direction of tape movement ("auto-reverse").
However, the system had been initially designed for dictation and portable use, with the audio quality of early players not well suited for music. Some early models also had unreliable mechanical design. In 1971 the Advent Corporation introduced their Model 201 tape deck that combined Dolby type B noise reduction and chromium dioxide (CrO2) tape, with a commercial-grade tape transport mechanism supplied by the Wollensak camera division of 3M Corporation. This resulted in the format being taken more seriously for musical use, and started the era of high fidelity cassettes and players.
During the 1980s, the cassette's popularity grew further as a result of portable pocket recorders and hi-fi players such as Sony's Walkman, which used a body not much larger than the cassette tape itself, with mechanical keys on one side, or electronic buttons or display on the face. Sony even made the WM-10 which was smaller than the cassette itself and expanded to hold and play a cassette.
As the transistor radio defined small music in the 1960s, the portable CD player in the 1990s, and the MP3 player in the 2000s, so did the Walkman define very small portable music in the 1980s, with cassette sales overtaking those of LPs. Total vinyl record sales remained higher well into the 1980s due to greater sales of singles, although cassette singles achieved popularity for a period in the 1990s.
Apart from the purely technical advances cassettes brought, they also served as catalysts for social change. Their durability and ease of copying helped bring underground rock and punk music behind the Iron Curtain, creating a foothold for Western culture among the younger generations. For similar reasons, cassettes became popular in developing nations.
One of the most famous political uses of cassette tapes was the dissemination of sermons by the Ayatollah Khomeini throughout Iran before the 1979 Iranian Revolution, in which Khomeini urged the overthrow of the regime of the Mohammad Reza Pahlavi.
In 1970s India, they were blamed for bringing unwanted secular influences into traditionally religious areas. Cassette technology created a booming market for pop music in India, drawing criticism from conservatives while at the same time creating a huge market for legitimate recording companies and pirated tapes. In some countries, particularly in the developing countries, cassettes still remain the dominant medium for purchasing and listening to music.
While cassettes and related equipment have become increasingly marginal in commercial music sales, recording on analog tape remains a desirable option for some.
Cassette tapes are made of a polyester type plastic film with a magnetic coating. The original magnetic material was based on gamma ferric oxide (Fe2O3). Circa 1970, 3M Company developed a cobalt volume-doping process combined with a double-coating technique to enhance overall tape output levels. This product was marketed as "High Energy" under its Scotch brand of recording tapes. Inexpensive cassettes are commonly labeled "low-noise", but typically are not optimized for high frequency response.
At about the same time chromium dioxide (CrO2) was introduced by BASF, and then coatings using magnetite (Fe3O4) such as TDK's Audua were produced in an attempt to approach the sound quality of vinyl records. Cobalt-adsorbed iron oxide (Avilyn) was introduced by TDK in 1974 and proved very successful. Finally pure metal particles (as opposed to oxide formulations) were introduced in 1979 by 3M under the trade name Metafine. The tape coating on most Cassettes sold today as either "Normal" or "Chrome" consists of Ferric Oxide and Cobalt mixed in varying ratios (and using various processes); there are very few cassettes on the market that use a pure (CrO2) coating.
Simple voice recorders are designed to work with standard ferric formulations. High fidelity tape decks are usually built with switches or detectors for the different bias and equalization requirements for high performance tapes. The most common, iron oxide tapes (defined by an IEC standard as "Type I"), use 120 µs playback equalization, while chrome and cobalt-absorbed tapes (IEC Type II) require 70 µs playback equalization. The recording "bias" equalizations were also different (and had a much longer time constant). Sony tried a dual layer tape with both ferric oxide and chrome dioxide known as 'ferrichrome' (FeCr) (IEC Type III) but these were only available for a short time in the 1970s. Metal Cassettes (IEC Type IV), also use 70 µs playback equalization, and provide still further improvements in sound quality, as well as improved resistance to wear. The quality is normally reflected in the price; Type I cassettes are generally cheapest, and Type IV usually the most expensive. BASF developed a chrome cassette designed for use with 120 µs (type I) playback equalization (for improved compatibility with equipment lacking a 70 µs setting) but this idea only caught on for commercially pre-recorded cassettes.
Notches on top of the cassette shell indicate the type of tape within. Type I cassettes only have write-protect notches, Type II have an additional pair next to the write protection ones, and Type IV (metal) have a third set in the middle of the cassette shell. These allow cassette decks to automatically detect the tape type and select the proper bias and equalization. Many inexpensive models (and the majority of those manufactured recently) may lack this feature. Playback of Type II and IV tapes on such a player will produce exaggerated treble, but it may not be noticeable because typically such devices have amplifiers that lack extended high frequency output. Recording on these units however results in very low sound reproduction and sometimes distortion and hiss is heard. Also, these cheaper units cannot erase high bias or metal bias tapes. Attempting to do so will result in "print-through".
Tape length is usually measured in minutes of total playing time. The most popular varieties are C46 (23 minutes per side), C60 (30 minutes per side), C90, and C120. The C46 and C60 lengths are typically 15–16 µm thick, but C90s are 10–11 µm and C120s are just 9 µm thick, rendering them more susceptible to stretching or breakage. Some vendors are more generous than others, providing 132 meters or 135 meters rather than 129 meters of tape for a C90 cassette. C180 and even C240 tapes were available at one time, but these were extremely thin and fragile and suffered badly from effects such as print-through, which made them unsuitable for general use. Other lengths are (or were) also available from some vendors, including C10 and C15 (useful for saving data from early home computers), C30, C50, C54, C64, C70, C74, C80, C84, C100, C105, and C110.
Some companies included a complimentary blank cassette with their portable cassette recorders in the early 1980s. Panasonic's was a C14 and came with a song recorded on side one, and a blank side two. Except for C74 and C100, such non-standard lengths have always been hard to find, and tend to be more expensive than the more popular lengths. Home taping enthusiasts may have found certain lengths useful for fitting an album neatly on one or both sides of a tape. For instance, the initial maximum playback time of Compact Discs was 74 minutes, explaining the relative popularity of C74 cassettes.
If later required, a piece of adhesive tape can be placed over the indentation to bypass the protection, or (on some decks), the lever can be manually depressed to record on a protected tape. Extra care is required to avoid covering the additional indents on high bias tape cassettes adjacent to the write-protect tabs.
The disadvantage with tape leaders was that the sound recording or playback did not start at the beginning of the tape, forcing the user to cue forwards to the start of the magnetic section. For certain applications such as dictation special cassettes containing leaderless tapes were made, typically with stronger material and for use in machines which had more sophisticated end of tape prediction.
The first cassette machines were simple mono record and playback units. Early machines required attaching an external dynamic microphone. Most units after the 1970s also incorporated built-in condenser microphones, which have extended high frequency response, but may also pick up noises from the recorder motor. A common portable recorder format still common today is a long box, the width of a cassette, with a speaker at the top, a cassette bay in the middle, and "piano key" controls at the bottom edge. The markings of "piano key" controls near the handle were soon standardized and is a legacy still emulated on many software control panels, though many DVD panels have eliminated the fast forward and rewind buttons in favor of next and previous tracks, which are only implemented on machines which have logic to search for blank spots in the tape. These symbols are commonly the square for stop, right pointing triangle for play, double triangles for fast forward and rewind, red dot for record, and a vertically-divided square (two rectangles side-by-side) for the pause button. Another format is only slightly larger than the cassette, also adapted for stereo "Walkman" player applications.
Stereo recorders eventually evolved into high fidelity and were known as "cassette decks", after the reel-to-reel "decks". Many formats of cassette players and recorders have evolved over the years. Initially all were top loading, usually with cassette on one side, VU meters and recording level controls on the other side. Older models used combinations of levers and sliding buttons for control.
A major innovation was the front-loading arrangement. Pioneer's angled cassette bay and the exposed bays of some Sansui models were eventually standardized as a front-loading door into which a cassette would be loaded. Later models would adopt electronic buttons, and replace conventional meters (which could be "pegged" when overloaded) with electronic LED or vacuum fluorescent displays, with level controls typically either being controlled by rotary controls or side-by-side sliders. BIC and Marantz briefly offered models which could be run at double speeds, but Nakamichi was widely recognized as one of the first companies to create decks which rivaled reel-to-reel decks with frequency response from the full 20–20,000 Hz range, low noise, and very low wow and flutter. The 3 headed closed-loop dual capstan Nakamichi 1000 (1973) is considered to be the first truly Audiophile High Fidelity Cassette Deck ever made. Unlike typical cassette decks, the recording and playback functions were split onto separate heads (with the third head being the erase head), allowing each to be optimized.
Other contenders for the highest, "HiFi" quality on this medium were two companies already widely known for their excellent quality reel-to-reel tape recorders: Tandberg and Revox (consumer brand of the Swiss professional Studer company for studio equipment). Tandberg started with combi-head machines like the TCD 300 and continued with the TCD 3x0 series with separate playback and recording heads. All TCD-models possessed dual capstan drives, beltdriven from a single capstan motor and two separate reel motors. Frequency range extended to 18 kHz. When Tandberg entered the much more competitive TV-market it folded and revived without the HiFi-branch these came from.
Revox went one step further: after hesitating long whether to accept cassettes as a medium capable for meeting their strict standards from reel to reel recorders at all, they produced their B710MK I (Dolby B) and MK II (Dolby B&C) machines. Both cassette units possessed double capstan drives, but with two independent, electronically controlled capstan motors and two separate reel motors. The head assembly moved by actuating a damped solenoid movement, eliminating all kind of belt drives and other wearable parts. These machines rivaled the Nakamichi in frequency and dynamic range. The B710MKII also achieved 20-20 kHz and dynamics of over 72 dB with Dolby C on chrome and slightly less dynamic range, but a larger headroom with metal tapes and Dolby C. Revox adjusted the frequency range on delivery with many years of use in mind: when new the frequency curve went upwards a few dB at 15-20 kHz, aiming for flat response after 15 years of use and headwear to match.
A last step taken by Revox produced even more advanced cassette drives with electronic finetuning of bias and equalization during recording. Revox also produced amplifiers, a very expensive FM tuner and a pickup with a special parallel arm mechanism of their own design. After which this company also got in financial difficulties and Studer had to save itself by folding its Revox-branch and all its consumer products (except their last reel to reel recorder the B77).
Note that while Nakamichi violated the tape recording standards to achieve the highest dynamics possible, producing non-compatible cassettes for playback on other machines, both Tandberg and Revox kept to the standards and produced cassettes which could be played back on other machines.
A third company, the well known Danish Bang & Olufsen invented a special, improved system for improving headroom at high frequencies, to reduce tape saturation despite lower bias levels. This "head room extension method, HX" was called Dolby HX Pro in full and patented. Their finest machine with HX Pro was the Beocord 8000, which indeed performed excellently as far as electronics were concerned. However, this machine possessed only one drive motor and many belt and wheels in a complicated arrangement. The effect, higher wow and flutter levels with less than perfect cassettes, did not make the B&O contender a popular choice with HiFi enthusiasts. Most of them favored Nakamichi, Tandberg or Revox instead, which all were mechanically much more reliable over the years. HX Pro was adopted by other manufacturers than B&O, Technics was one of them.
As they became aimed at more casual users, fewer decks had microphone inputs. Dual decks became popular and incorporated into home entertainment systems of all sizes for tape dubbing. Although the quality would suffer each time a source was copied, there are no mechanical restrictions on copying from a record, radio, or another cassette source. Even as CD recorders are becoming more popular, some incorporate cassette decks for professional applications.
Another format that made an impact on culture in the 1980s was the "boom box" which combined the portable cassette deck with speakers capable of producing significant sound levels. The boom box became synonymous with urban youth culture in entertainment, which led to the somewhat derisive nickname "ghetto blaster".
Applications for car stereos varied widely. Auto manufacturers in the U.S. would typically fit a cassette slot into their standard large radio faceplates. Europe and Asia would standardize on DIN and double DIN sized faceplates. In the 1980s, a high end installation would have a Dolby AM/FM cassette deck, and they rendered the 8-track cartridge obsolete in car installations because of space, performance and audio quality. As the cost of building CD players declined, many manufacturers offered a CD player, but some cars, especially those targeted at older drivers still offer the option of a cassette player, either by itself, or sometimes in combination with a CD slot. The newest cars often are not designed to accommodate any cassette drive, but the auxiliary jack advertised for MP3 players can also be used with portable cassette players.
Although the cassettes themselves were relatively durable, the players required regular maintenance to perform properly. Head cleaning may be done with long swabs, or cassette-shaped devices that could be inserted into a tape deck to polish the heads and remove smudges and dirt. Similarly shaped demagnetizers used magnets to degauss the deck, which kept sound from becoming distorted. A common mechanical problem occurred when a worn-out or dirty player rotated the supply spool faster than the take-up spool or failed to release the heads from the tape upon ejection. This would cause the magnetic tape to be fed out through the bottom of the cassette and become tangled in the mechanism of the player. In these cases the player was said to have "eaten" the tape, and it often destroyed the playability of the cassette altogether, and resulted in the common sight of tangled tape on the side of the road. Cutting blocks, analogous to those used for open reel 1/4" tape, were readily available though, but mainly used for retrieving valued recordings, through removing the damaged portion of, or repairing the break in, the tape. Creation of compilations was usually by re-recording rather than splicing sections of songs because of the much smaller tape area.
The Compact Cassette was originally intended for use in dictation machines. In this capacity, some later-model cassette-based dictation machines could also run the tape at half speed (15⁄16 in/s) as playback quality was not critical. The Compact Cassette soon became a popular medium for distributing prerecorded music—initially through The Philips Record Company (and subsidiary labels Mercury and Philips in the U.S.). As of 2006, one finds cassettes used for a variety of purposes such as journalism, oral history, meeting and interview transcripts and so on. However, they are starting to give way to Compact Discs and more "compact" storage media.
In the simplest configuration, rather than playing a pair of stereo channels of each side of the cassette, the typical "portastudio" used a four-track tape head assembly to access four tracks on the cassette at once (with the tape playing in one direction). Each track could be recorded to, erased or played back individually, allowing musicians to overdub themselves and create simple multitrack recordings easily, which could then be mixed down to a finished stereo version on an external machine. To increase audio quality in these recorders, the tape speed was sometimes doubled in comparison to the standard; additionally, dbx, Dolby B or Dolby C noise reduction provided compansion (compression of the signal during recording with equal and opposite expansion of the signal during playback), which yields increased dynamic range by lowering the noise level and increasing the maximum signal level before distortion occurs. Multi-track cassette recorders with built-in mixer and signal routing features ranged from easy-to-use beginner units up to professional-level recording systems.
Most cassettes were sold blank and used for recording (dubbing) the owner's records (as backup or to make mixtape compilations), their friends' records or music from the radio. This practice was condemned by the music industry with such slogans as "Home Taping Is Killing Music". However, many claimed that the medium was ideal for spreading new music and would increase sales, and strongly defended at least their right to copy their own records onto tape. For a limited time in the early 1980s Island Records sold chromium dioxide “One Plus One” cassettes that had an album prerecorded on one side and the other was left blank for the purchaser to use. Cassettes were also a boon to people wishing to tape concerts (unauthorized or authorized) for sale or trade, a practice tacitly or overtly encouraged by many bands with a more counterculture bent such as the Grateful Dead. Blank Compact Cassettes also were an invaluable tool to spread the music of unsigned acts, especially within Tape trading networks.
Various legal cases arose surrounding the dubbing of cassettes. In the UK, in the case of CBS Songs v. Amstrad (1988), the House of Lords found in favor of Amstrad that producing equipment that facilitated the dubbing of cassettes, in this case a high-speed twin cassette deck that allowed one cassette to be copied directly onto another, did not constitute the infringement of copyright. In a similar case, a shop owner who rented cassettes and sold blank tapes was not liable for copyright infringement even though it was clear that his customers were likely dubbing them at home. In both cases, the courts held that manufacturers and retailers could not be held accountable for the actions of consumers.
As an alternative to home dubbing, in the late 1980s, the Personics company installed booths in record stores across America which allowed customers to make personalised mixtapes from a digitally-encoded back-catalogue with customised printed covers.
The Hewlett Packard HP 9830 was one of the first desktop computers in the early 1970s to use automatically controlled cassette tapes for storage. It could save and find files by number, using a clear leader to detect the end of tape. These would be replaced by specialized cartridges such as the 3M DC-series. Many of the earliest microcomputers implemented the Kansas City standard for digital data storage. Most home computers of the late 1970s and early 1980s could use cassettes for data storage as a cheaper alternative to floppy disks, though users often had to manually stop and start a cassette recorder. Even the first version of the IBM PC of 1981 had a cassette port and a command in its ROM BASIC programming language to use it. However, this was seldom used, as even then floppy drives had become commonplace in high-end machines.
The typical encoding method for computer data was simple FSK which resulted in typical data rates of 500 to 2000 bit/s, although some games used special faster loading routines, up to around 4000-bit/s. A rate of 2000-bit/s equates to a capacity of around 660 kilobytes per side of a 90-minute tape.
Among home computers that primarily used data cassettes for storage in the late 1970s were Commodore PET (early models of which had a cassette drive built-in), TRS-80 and Apple II Plus, until the introduction of floppy disc drives and hard drives in the early 1980s made cassettes virtually obsolete for day-to-day use in the US. However, they remained in use on some portable systems such as the TRS-80 Model 100 line until the early 1990s. Due to the high price of disks, cassettes also remained the primary data storage medium for 8-bit computers in many countries (for example, the UK, where 8-bit software was mostly sold on cassette until that market disappeared altogether in the early 1990s.)
In some countries, including Scotland, Poland, Hungary and the Netherlands, audio cassette data storage was so popular that some radio stations would broadcast computer programs that listeners could record onto cassette and then load into their computer. See BASICODE.
The use of better modulation techniques like QPSK or those used in modern modems, combined with the improved bandwidth and signal to noise ratio of newer cassette tapes, allowed much greater capacities (up to 60 MB) and speeds (10–17 kB/s for data rate) on each cassette. These were typically used as hard disk backup for PCs in the late 1980s. They also found use during the 1980s in data loggers for scientific and industrial equipment.
Technical development of the cassette effectively ceased when digital recordable media such as DAT and MiniDisc were introduced in the late 1980s and early 1990s. Anticipating the switch from analog to digital, major companies such as Sony shifted their focus to new media. In 1992, Philips introduced the Digital Compact Cassette (DCC), a DAT-like tape in the same form factor as the compact audio cassette. It was aimed primarily at the consumer market. A DCC deck could play back both types of cassettes. Unlike DAT, which was accepted in professional usage because it could record without lossy compression effects, DCC failed in both home and mobile environments, and was discontinued in 1996.
The microcassette has in many cases supplanted the full-sized audio cassette in situations where voice-level fidelity is all that is required, such as in dictation machines and answering machines. Even these, in turn, are starting to give way to digital recorders of various descriptions. Since the rise of cheap CD-R discs, and flash memory-based digital audio players, the phenomenon of "home taping" has effectively switched to recording to Compact Disc or downloading from commercial or music sharing websites.
Because of consumer demand, the cassette has remained influential on design over a decade after its decline as a media mainstay. As the Compact Disc grew in popularity, cassette-shaped audio adapters were developed to provide an economical and clear way to obtain CD functionality in vehicles equipped with cassette decks. A portable CD player would have its analog line-out connected to the adapter, which in turn fed the signal to the head of the cassette deck. These adapters continue to function with MP3 players as well, and are generally more reliable than the FM transmitters that must be used to adapt CD players to MP3s. MP3 players shaped as audio cassettes have also become available, which can be inserted into any tape player and communicate with the head as if they were normal cassettes.
Better-made compact cassettes are held together by a number of screws, so that they may be disassembled and reassembled. It may be helpful to practice the procedure on blank cassettes first. Care should be taken to ensure that the tape follows the correct path through the cassette before reassembly, and that all of the small parts are in their proper places. If the original, worn cassette is glued together instead of held together by screws, it can be cracked progressively open by inserting a thin blade of metal (such as a screwdriver or knife blade) in the seam between the halves of the cassette shell, while exercising care not to gouge or damage the reels.
The spools upon which the tape is wound are often slotted so that the end of the tape may be freed from one spool and secured to a new spool.
Two other common problems with cassette tapes are: 1) the tape winds unevenly inside the plastic case over time which gives rise to jamming during playback or rewinding, and 2) the felt pressure pad that contacts the magnetic tape eventually falls off. Two solutions: 1) slap the cassette on a flat surface several times and then rewind the tape all the way through without pause (this may have to be tried several times). 2) replace the part composed of the copper and felt pressure pad unit from an unused cassette tape.