Speed of Audio Tape

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Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Alten, Stanley R. Audio in Media. Belmont, CA: Wadsworth, 1999: 98. "30 ips, 15 ips, 7½ ips, 3¾ ips" 76 cm/s
38 cm/s
19 cm/s
9.5 cm/s
Encyclopedia Americana. Grolier, 1999: V26, 279. "Typical home or professional audio recorders operating at 7½ inches and 15 inches per second …. Cassette recorders which operate at 1⅞ inches per second" 38 cm/s
19 cm/s
4.75 cm/s
Daily, Jay E. Cataloging Phonorecordings Problems and Possibilities. Marcel Dekker, Inc., 1975: V1, 5 "The fastest speed … is 15 inches per second or 38 cm per second. Most tape decks include 7½, 3¾, and 1⅞ ips speed …. so that the slowest speed is 1⅞ ips." 38 cm/s
19 cm/s
9.5 cm/s
4.75 cm/s
Earl, John. Cassette Tape Recorders. New York: Fountain, 1977: 34. "… at a tape speed of 4.75 cm/s (the cassette tape)" 4.75 cm/s
Tape Speed. Zen Audio Project (ZAP). Simon Fraser University. "Cassettes run at 1.875 inches per second (4.75 cm/second) while some 4 track cassette devices ("portastudios") run at 3.75 i/s (9.5 cm/s). Reel to reel tape runs at 7.5 i/s (or 19 cm/s) and 15 i/s (38 cm/s)- the latter being the professional standard. Occasionally one may find analogue machines set to run at 30 i/s (76 cm/s)." 38 cm/s
19 cm/s
9.5 cm/s
4.75 cm/s

Analog tape systems run at a variety of speeds depending on type. There are two basic types of audio tape: open reel and cassette.

The larger open reel-to-reel tapes typically run at 7½ inches per second (19 cm/s) and 15 inches per second (38 cm/s) -- the later being the professional standard. Occasionally, you may find analog machines set at 30 inches per second (76 cm/s). The fastest speeds are reserved for professional use because they have the greatest range due to less wow and flutter and greater frequency response. Wow is a relatively slow variation in the frequency of reproduced sound caused by slow speed variations in records, tape recorders, etc. Pitch fluctuations of one or two per second are classified as wow, while faster variations are called flutter. Wow and flutter are almost never an issue in digital recorders because tape speed has no direct effect on the pitch of the audio playback or recording.

The quality of sound decreases as speed is reduced. Reproduction quality also fades as speed decreases so that the slowest tape speed of 1⅞ inches per second (4.8 cm/s) is unsuitable for professional use. However, only a very sophisticated device can detect the difference between 15 inches per second and 7½ inches per second. For almost every kind of music one is just as good as the other. Also, a minimum of 7½ inches per second is required to physically cut or edit tape.

Cassette tapes on the other hand are much smaller in size. They typically run at 1⅞ inches per second (4.8 cm/s), however, some four track cassette devices run at 3¾ inches per second (9.5 cm/s).

Tien-Huey Heh -- 2000


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