By CRAIG STARK
MORE STANDARDS
LAST month I pointed out how rapid technological developments in tape oxides, heads, and electronics threaten to make some of our present-day cassette standards obsolete. Perhaps the most obvious outgrowth of this situation is the incorporation of two- or three-position "bias/equalization" switches on today's better cassette machines to adapt them to some of the proliferating varieties of tape types. But since many manufacturers have felt free to go their own ways in determining the equalization characteristics these switches intro duce, a cassette made on one brand of machine may not have precisely the same frequency response when played back on another. That's just the sort of thing standards are meant to prevent.
Open-reel standards, of course, have a longer history: the NAB (National Association of Broadcasters) adopted its first recommendations in 1942. In April 1965 it issued the current standards, updating those of 1953. Now nearly a decade old, these too cry out for some revision. There was agreement among he experts at the last Midwest Acoustics Conference, for example, that, for the speed of 15 ips (inches per second), industry practice has pretty much made the old standards obsolete. At the professional level this poses little difficulty, or studio recorders are adaptable to variety of equalizations.
Home recorders, however, operating t the customary speeds of 7 1/2 and 3 3/4 ips, present a greater problem. Bluntly put, none of them can be guaranteed to meet the current NAB standards. The fault is not in the machines, for many of hem are better than "professional" models of but a few years ago. The problem, rather, is that current NAB measurements of record level, frequency response, and signal-to-noise ratio are all referenced to an "NAB Standard Test Tape" that, almost ten years after its announcement, has yet to be produced! The reasons have a lot to do with bus ness politics: which company is to get the distinction and other benefits of producing the "official" NAB tapes? There's more than "petty cash" involved, however. In Europe there are voluminous DIN (Deutsche Industrie Normen) standards, together with avail able reference tapes in each format containing a blank section--so that you can check not only the playback frequency response, but overall record-playback performance as well. They illustrate the other horn of the dilemma, however: suppose a tape manufacturer comes up with a product with a much "hotter" high-end response (for example, greater sensitivity at 15,000 Hz)? Adjusting your machine to the "standard" tape would put it way out of specification for the improved tape, and vice versa.
In short, while tape standards are not intended to put a strait jacket on techno logical innovation, in reality they do. No one will change the production adjustments of his machines for a minor, probably unnoticeable, improvement; and a radical improvement must prove itself over some period of time before achieving acceptance.
Somehow, however, American open-reel manufacturers manage to muddle through, for they have at least a stop gap standard: the Ampex "Reproducer Alignment Tapes." Produced individually (and hence at considerable cost per tape), they don't cover the full range of the NAB-specified frequency-response tests, and there's a question whether their recorded levels conform to the N AB's standard "operating level." Further, they check playback only, leaving each recorder manufacturer (and equipment reviewer!) free to pick any tape he wishes for record-playback tests.
With all the problems, however, the consensus seems to be that for the 7 1/2- and 3 3/4-ips speeds, industry practice comes very close to optimum open-reel equalization. But with the present pace of technological advancement, a lack of comprehensive standards is likely to be a real problem later.
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Also see:
GOING on RECORD, JAMES GOODFRIEND