Metal tape proves its value

September 23, 1990|By Hans Fantel | Hans Fantel,New York Times News Service

Belated recognition has come to metal tape cassettes. These are tapes coated with particles of metal alloy instead of the usual metal oxide particles. Such tapes languished on the market for more than a decade, but now their advantage is being appreciated.

In the past, audio fans balked at the higher price of such tapes -- typically about 30 percent above the cost of ordinary high-quality tapes -- because they really couldn't hear much difference.

This situation has changed with the advent of compact disks, which made the difference clearly apparent. When listeners tried to copy CDs onto tapes, they found that conventional tapes could not capture the full range of sound contained on digital recordings.

Neither the topmost frequencies nor the full span between the loudest and softest passages on a CD could be transferred to conventional oxide-coated tapes.

As a result, cassette copies of CDs often lacked the brilliance of the original, and the sound became harsh and distorted in the more forceful musical passages.

Metal tape, by contrast, proved better suited to the task of copying CDs, which explains their recent popularity.

Responding to rising demand, several companies have introduced new formulations of metal tape; they include Denon's HD-M, Sony's Metal-XR, TDK's MA, Fuji's FR-Metal, Maxell's MX and That's MG-X. Tapes in this group are priced between $5 and $9 for a 90-minute cassette, though they are often sold at discount.

Comparison tests have shown them to be similar in performance, which makes it hard to name any single standout.

However, TDK's MA probably represents the best dollar value, being at the low end of the price spectrum and the high end of performance measurements.

Just what distinguishes metal tapes from the less expensive and more widely used oxide tapes? Oxide tapes, after all, work well enough in most situations. However, they balk at extremely loud musical passages because the oxide particles become magnetically saturated by such signals.

They can no longer respond accurately, and the musical waveforms become distorted.

Avoiding such distortion is the main reason for watching the recording meter on the tape deck while the music is being recorded.

Whenever the meter indicates an overload due to volume peaks, the recording level must be lowered to keep the sound clear and true.

At the same time, a lower limit on recording volume must also be observed. For if the music becomes too soft, it may be obscured by the residual hiss of the tape.

The spread between these upper and lower loudness limits represents the usable dynamic range of the cassette, and all the music must be squeezed within these limits.

This means that the soft passages may have to be made a little louder, and the loud passages a little softer. This is nearly always done, to some degree, on LP recordings and in radio broadcasting.

Consequently, LPs and radio broadcasts can usually be recorded on ordinary oxide tapes without exceeding the capabilities of the tape.

Not so with digital disks, whose dynamic range exceeds that of ordinary oxide tapes. Metal tapes represent an attempt to bridge this discrepancy.

Admittedly, not even metal tapes quite match the dynamic range of a sonically vigorous CD. But they come far closer than oxide tapes because their metal-alloy particles accept higher levels of magnetic force.

This enables them to cope more easily with the expanded dynamics of digital sound.

To express this difference in numerical terms, metal tapes surpass oxide tapes by about 8 to 10 decibels of peak signal capacity.

This extra margin -- rarely noticed when copying the relatively tame sound of LPs or radio broadcasts -- becomes very noticeable in taping digital sound sources.

It accounts for added clarity even in climactic moments. And since loud passages fall within the range of the tape, it is no longer necessary to sit at the tape recorder, ready to lower the recording level whenever the music rises in a crescendo.

In sum, metal tape permits the transfer of CDs to cassette with the least sonic loss. To many audio fans, this justifies the higher price.

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