754 Chapter 26
induced current in the playback head are heavily distorted with respect to frequency
and must both be equalized. This is an area where standardization between different
manufacturers is particularly important because, without it, tapes recorded on one
machine would not be reproducible on another.
In itself, this would not be such a problem were it not for the fact that, due to differences
in head geometry and construction, the electrical equalization differs markedly from
manufacturer to manufacturer. The IEC provided an ingenious solution to widespread
standardization by providing a series of standard prerecorded tapes on which are recorded
frequency sweeps and spot levels. The intention was that these must be reproduced
(played back) with a level fl at-frequency response characteristic, with the individual
manufacturer responsible for choosing the appropriate electrical equalization to affect this
situation. This appears to leave the situation concerning record equalization undefi ned,
but this is not the case because it is intended that the manufacturer chooses record
equalization curves so that tapes recorded on any particular machine must result in a fl at-
frequency response when replayed using the manufacturer’s own IEC standard replay
equalization characteristic.
The issue of “ portability ” should not be overlooked, and any serious studio that still
relies on analogue recording must ensure that its analogue tape equipment is aligned
(and continues to remain aligned—usually the duty of the maintenance engineer) to the
relevant IEC standards. This, unfortunately, necessarily involves the purchase of the
relevant standard alignment tapes.
26.6 Tape Speed ............................................................................................................
Clearly another (in fact, the earliest) candidate for standardization was the choice of linear
speed of the tape through the tape path. Without this the signals recorded on one machine
replay at a different pitch when replayed on another. While this effect offers important
artistic possibilities (see later in this chapter), it is clearly undesirable in most operational
circumstances. Table 26.1 lists the standard tape speeds in metric (centimeters per second,
cm/s) and imperial measures (inches per second, ips) and their likely applications.
26.7 Speed Stability ......................................................................................................
Once standardized, the speed of the tape must remain consistent over both long and short
terms. Failure to establish this results in audible effects known, respectively, as wow and