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What is the Hardwired A-B Test and what precautions do I need to take?

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This test is a matter of setting up two identical microphones, into a mixer, one connected with an audio cable and the other with a wireless system, to perform a listening test. An even better way to perform the test is to split a single mic signal so that one path is through the wireless mic system to the mixer and the other is hardwired to the mixer. Though seemingly simple, there are several mistakes that can really mess up the results:

  1. The listening levels of both paths must be EXACTLY the same. Even a very slight difference in level will “fool” the ears into hearing differences that may not actually exist.
  2. The test absolutely requires two people. One person speaking and the other person listening. A single person hears the sound coming from their own mouth and the sound coming from the sound system and the sounds combine at their ears to give very misleading results. This particularly true with systems that have audio delays (digital wireless systems or mixers). Even having the two people in the same room is enough to mess up the results. The only way to do the test with one person is to use a very high quality, pre-recorded signal as the source.
  3. Keep in mind that the truer system is not the one that sounds brighter or warmer or bassier but the one that sounds most like the hardwired signal. You'd be surprised how many people ignore this fact.
  4. If you have to use two microphones, it is always a good idea to swap the microphones and listen to them a second time to see if there are slight differences in the microphones themselves that may have been detected in the first comparison.
  5. If you have to use two microphones make sure they are positioned exactly the same from a sound source or someone’s mouth so the the same audio signal enters both microphones.
  6. Slight amounts of background hiss will make the overall sound of that signal seem brighter. It is a known pre-sensitization effect in the ear. Make sure that the gain of the wireless system is set properly so that background hiss is minimized.
  7. If at all possible, use headphones. Again, it's not whether you like the sound it is how close is the wireless system path to the direct wired path. Headphones are much more analytical and make it many times easier to hear small errors in sound reproduction.

Switch back and forth between the cabled and the wireless setup as the listener compares the sound of each setup. This, of course, is best done in a “blindfold” manner where the listener has no way of telling which setup is being monitored, and by writing down a few notes about the results.

Posted 1 year agoby LectroAdmin
#75