Editing Cassette tape (section)

== Tape types ==
[[File:Cassette Write Protect IV.jpg|thumb|right|Notches on the top surface of the Compact Cassette indicate its type. The rear-most cassette at the top of this picture, with only write-protect notches (here covered by write-protect tabs), is '''Type I, its tape consisting of iron oxide'''. The next cassette down, with additional notches adjacent to the write-protect tabs, is '''Type II, its tape consisting of chrome and cobalt'''. The bottom two cassettes, featuring the Type II notches plus an additional pair in the center of the cassette, are '''Type IV (metal)'''; note the removal of the tabs on the second of these, meaning the tape is write-protected. Type III was a combination of Types I and II but never gained the popularity of the other three types and was made obsolete by Type IV.]]
{{further|Compact Cassette tape types and formulations}}

Cassette tapes are made of a polyester-type plastic film with a magnetic coating. The original magnetic material was based on gamma [[ferric oxide]] (Fe<sub>2</sub>O<sub>3</sub>). {{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.<ref name="VTH">{{cite web |title=History of Compact Cassette |url=http://vintagecassettes.com/_history/history.htm |access-date=4 June 2012 |archive-date=26 February 2011 |archive-url=https://web.archive.org/web/20110226024807/http://vintagecassettes.com/_history/history.htm |url-status=live }}</ref> Inexpensive cassettes commonly are labeled "low-noise", but typically are not optimized for high [[frequency response]]. For this reason, some low-grade [[International Electrotechnical Commission|IEC]] Type I tapes have been marketed specifically as better suited for data storage than for sound recording.{{citation needed|date=April 2019}}

In 1968,<ref>{{cite journal |last=Canby |first=Tatnall |year=1968 |title=CrO2 - Tomorrow's Tape |journal=Studio Sound |issue=5 |pages=239}}</ref> [[DuPont]], the inventor of a [[chromium dioxide]] (CrO<sub>2</sub>) manufacturing process, began commercialization of CrO<sub>2</sub> media. The first CrO<sub>2</sub> cassette was introduced in 1970 by [[Advent Corporation|Advent]],<ref>{{cite journal |last=Stark |first=Craig |year=1992 |title=Choosing the Right Tape |journal=Stereo Review |issue=March |pages=45–48}}</ref> and later strongly backed by [[BASF]], the inventor and longtime manufacturer of magnetic recording tape.<ref name="Abelshauser">{{Cite book |author1=Werner Abelshauser |url=https://archive.org/details/germanindustrygl00wern/page/585 |title=German Industry and Global Enterprise: BASF: The History of a Company |author2=Wolfgang von Hippel |author3=Jeffrey Allan Johnson |author4=Raymond G. Stokes |publisher=Cambridge University Press |year=2003 |isbn=978-0-521-82726-3 |page=[https://archive.org/details/germanindustrygl00wern/page/585 585]}}</ref> Next, coatings using [[magnetite]] (Fe<sub>3</sub>O<sub>4</sub>) such as [[TDK]]'s Audua were produced in an attempt to approach or exceed the sound quality of [[vinyl record]]s. [[Cobalt]]-''[[Adsorption|adsorbed]]'' iron oxide (Avilyn) was introduced by TDK in 1974 and proved very successful. "Type IV" tapes using 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 as of 2024 are 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 (CrO<sub>2</sub>) coating.<ref name="Daniel" />

Simple voice recorders and earlier cassette decks are designed to work with standard ferric formulations. Newer tape decks usually are built with switches and later detectors for the different [[tape bias|bias]] and [[Equalization (audio)|equalization]] requirements for higher grade tapes. The most common are iron oxide tapes (as defined by the [[List of IEC standards|IEC 60094 standard]]).<ref name="IEC" />

Notches on top of the cassette shell indicate the type of tape. Type I cassettes have only [[Write protection|write-protect]] notches, Type II have an additional pair next to the write protection ones, and Type IV (metal) have a third set near the middle of the top of the cassette shell. These allow later [[cassette deck]]s to detect the tape type automatically and select the proper bias and equalization.<ref>{{Cite web |title=Which Type of Audio Cassette Tape is Right for You : Type 1, 2 or 4 ? - Cassette Player Culture |url=https://www.cassette-player.com/right-audio-cassette-tape-for-you |url-status=live |archive-url=https://web.archive.org/web/20240702081211/https://www.cassette-player.com/right-audio-cassette-tape-for-you |archive-date=2024-07-02 |access-date=2024-07-02 |website=cassette-player.com }}</ref>