Listen and Learn

For most people in the live sound industry, ear training is a fundamental part of their skill set. The ability to recognize defects in the sound produced by microphones, mixers, processing gear, power amps and loudspeakers is essential to running an reliable rig. The correlation between a specific sound quality and the likely culprit must be learned first hand. This knowledge can make the difference between a ten-minute solution to the problem and two days of searching for the source of the odd sound. Equally important is the ability to judge a show-stopping defect (during the sound check) and something that simply needs to be added to the maintenance items for the next break performance schedule.

Embracing new technology requires that ear training also be included in the process. This is an area of product familiarity that can be difficult to assess. Can you hear the difference between the A/D converter overloading and clipping produced by gain structure problems within the processor? Can you detect the artifacts of a distressed loudspeaker controller? These types of products seem to appear in a continuous stream from manufacturers. The experience of the past few decades using analogue signal chains may now only represent a small proportion of the potential problems in the sound system as digital audio processors are incorporated into the system.

In assessing the latest products, a bench test should include listening to the output of the unit through a very familiar loudspeaker (except, of course, loudspeaker processors and powered loudspeakers where you may have to deal with two or more variables at once). It is necessary to place the new device under every conceivable type of stressful signal condition, environmental condition and load condition while listening to the result. This is especially difficult with loudspeaker processors and powered loudspeakers. The SPL levels generated before many high-efficiency devices begin to be audibly distressed are beyond the safe limits of most bench test environments. You can wear hearing protection but that may mask or at least significantly alter the very qualities you are listening for. The ideal situation for testing these types of devices may be outdoors, at a safe distance (courtesy of the inverse-square law) from the loudspeaker. Unfortunately, the distance will also cause other effects, such as reflections from thermal gradients in the air and high-frequency rolloff due to the non-linear nature of air absorption.

Some of the audible quirks of DSP devices can be the product of the DSP code and can change throughout the production life of the product, just like circuit revisions in analogue devices. This requires diligence to ensure that your personal library of audible fault conditions remains current.

The side benefit of this ear training process is that the thorough test procedure will increase your familiarity with the functional controls of the unit. It is always important to remember that the evaluation of a new product should include both measurement and listening tests. The measurement of any device is only valid if you have developed a correlation between the resulting data and practical implementation of the unit. This may include listening to the results of less than ideal electrical conditions (such as low load impedance, low power line voltage, balanced/unbalanced connection permutations, and high levels of electro-magnetic background noise). All of these conditions may cause degradation of the measured performance but some may cause audible artifacts that become objectionable before the unit is even out of spec. Be skeptical, listen and learn.

United Entertainment Media Inc.
460 Park Avenue South, 9th Floor
New York, NY, 10016
Ph. 212-378-0400
FAX 212-378-2160

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