IEC 60094-1: Magnetic Tape Recording Systems — The Golden Age of Analogue Audio

Magnetic Tape Standards: The Critical Reference When Digitizing 1960s–1990s Audio Archives

IEC 60094-1 specifies analogue magnetic tape recording parameters: tape speed, track configuration, and equalization curves. When libraries and archives digitize historical audio recordings, this standard is the sole reference for correct playback parameters.

Critical parameters: Tape speeds of 4.76 cm/s (cassette) and 19.05/38.1 cm/s (open-reel). Equalization curves are the most error-prone aspect — NAB (North American) and IEC/CCIR (European) standards have different high-frequency turnover points. Using the wrong equalization curve severely distorts high frequencies — making the audio sound “muffled” or “harsh.”

Archival best practice: When the original recording equalization standard is unknown, professional archives digitize twice — once with NAB and once with IEC equalization — then use spectral analysis to determine which version better matches the original sound.

TN Lab — Tapes may demagnetize, but standards preserve the parameters needed to correctly restore historical sound.