Compact cassette tapes were extremely popular in 80s and early 90s as the main audio medium for home music listening. So what are the differences between the different types of cassette formulations?
Type I (IEC I, ‘ferric’ or ‘normal’ tapes) included pure gamma ferric oxide formulations and was the cheapest to produce and purchase. They dominated the prerecorded and home cassette market. You can tell by looking at the top of the cassette as they only have 2 write protection notches at the top of the tape.
Type II (IEC II, or ‘chrome’ tapes) included ferricobalt and chromium dioxide formulations. Historically, they are known as chromium dioxide tape or simply chrome tape even though they do not contain chromium. Type II cassettes have 2 write protection notches as well as 2 notches to tell the cassette player which EQ/bias to use. These cassettes can playback and record higher frequencies than Type I.
Type IV (IEC IV, or ‘metal’ tapes) included metal particle tapes. These cassettes were the more expensive, could take much higher sound levels than a chrome, whilst reproducing equal or better high frequency. Type IV cassettes have 2 write protection notches as well as 4 notches.
As any cassette enthusiast would tell you, capturing the high end frequency of music recordings is a top priority. But the full range is also important and you can see below the advantages of Type II and Type IV cassettes across the full spectrum. Even with Type II cassettes, some brands had different formulations that can come close to achieving Type IV results.
Here is a frequency sweeps test for one TDK’s different tape formulations: TDK D Type I, TDK AD Type I, TDK SA Type II, TDK SA-X Type II, and TDK MA Type IV cassettes.
