What Is The Answer?
In order to arrive at the ultimate metering methods for use in modern recording systems, I think we should look closely at the requirements.

The basic requirement is the same as it has always been…to enable us to record in the optimum region between noise and distortion.

This can best be accomplished by placing the recorded signal as near the distortion point as possible without crossing that fine line into audible degradation.

Distortion, obviously, is an instantaneous function of the waveform. As such, the only way to accurately control it is to be able to meter the instantaneous (or peak) levels of signal.

Once we have this sort of metering, we can establish an accurate correlation between meter reading and amount of the distortion introduced.

In order that the meter be capable of measuring high frequency transients properly, it is desirable that its attack time be on the order of 100 microseconds or less. This attack, or upwards deflection must then be followed by a slower release time (or downward deflection), for two reasons.

First, so that the human eye will be capable of following the meter movement easily. Secondly, so that the meter will tend to integrate a rapid passage of high frequency peaks into a readable display. This would call for release times on the order of 25 to 100 milliseconds.

Judging from the current state of the art, it would appear that such a meter would, in all probability, be one utilizing a segmented light display.

To accomplish the desired degree of accuracy in such a meter, the number of segments should be in excess of fifteen. Otherwise the dB difference between increments will tend to be too great for accurate readout.

Additionally, there is a question as to the desirability of a single spot of light. Tests conducted in a recording studio environment have shown a single moving point of light display to be much more readable and considerably less fatiguing to the eye, than a widening line of light. It has been further observed that each increment of light must be either “on” or “off.”

That is to say that no segment should be allowed to be half on or dimly lit while its companion is in “on” mode. Should this not be the case, readability suffers and eye fatigue tends to increase.

It is definitely within the realm of our industry to develop such a device. When the hardware has been developed, the progressive engineer will have little choice but to change his thinking from VU metering to “Peak Level Metering.”

This, of course, will require the establishment of a new set of ground rules in the area of studio level measurements and will almost certainly result in a large number of “Bah Humbugs.”

We do seem to recall, some years ago, several chorus’ of “Bah Humbug” when someone wrote an article entitled “WHAT’S WRONG WITH THE GOOD OLD VACUUM TUBE? . . .

 
Downloadable Media
Original Article (pdf)
Original Cover (pdf)

Take the PSW Photo Gallery Tour of audio equipment ads appearing in RE/P magazine, circa 1970

Editor’s Note: This is a series of articles from Recording Engineer/Producer (RE/P) magazine, which began publishing in 1970 under the direction of Publisher/Editor Martin Gallay. After a great run, RE/P ceased publishing in the early 1990s, yet its content is still much revered in the professional audio community. RE/P also published the first issues of Live Sound International magazine as a quarterly supplement, beginning in the late 1980s, and LSI has grown to a monthly publication that continues to thrive to this day.

Our sincere thanks to Mark Gander of JBL Professional for his considerable support on this archive project.

Please send all questions and comments to ProSoundWeb Editor .(JavaScript must be enabled to view this email address).

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