text: During the many years that cassette decks were popular, many audio magazines published comparative measurements of the performance characteristics of the wide variety of different tapes that were available in the marketplace.  These measurements typically included parameters such as MOL, SOL, frequency response at 0-dB and −20-dB re Dolby Level, signal-to-noise ratio, modulation noise, bias level, and sensitivity. The first figure shows frequency response plots for sample TypeI, TypeII, and TypeIV cassette tapes comparing their MOL, SOL, and 0-dB performance.
  The second figure shows the frequency response performance of typical TypeI, TypeII, and TypeIV cassette tapes, obtained for a number of different input signal levels, using a high quality Pioneer CT-93 stereo cassette deck from the 1990s. For each of the three tape formulations, the record/replay characteristics of the cassette deck were aligned with the relevant IEC Reference Tape, and each tested tape was measured with the bias and equalization unchanged from that reference position. The record/replay frequency response was tested at four levels: +6VU, 0VU, −10VU and −20VU (Dolby Level is marked at +3VU for the CT-93). Thus, these plots provide data 
  on the linearity of the different tape formulations at both high and moderate recording levels. It is interesting to note that the TypeI tape shows +6VU and at 0VU responses that are much flatter than that of the TypeII tape. At +6VU, the TypeII tape displays significant amounts of signal level compression across the entire frequency range, reducing to about 2dB of signal compression between 80Hz and 1kHz.
  Some representative measured performance characteristics of a small number of commercially available tape types are presented in the table below.