Lateral Reflections 1/3

Published On: August 7, 2020Tags:
A New Format

By popular demand, Art Noxon’s original notebook material shall be presented without any fancy formatting, zooming, or image adjustment. The text is presented below to supplement the original. This week’s discussion focuses on a well-known nemesis: early side wall reflections.


photo of hand drawn graphs and illustrations regarding Lateral ReflectionsLateral Reflections…

…are very significant in the listening experience. We have 2 ears, which allows us to be very perceptive of incoming lateral sound. In HiFi, sidewall reflections are known to change the stereo imaging effect. The rule of thumb is to weaken or eliminate these early lateral reflections.

The most commonly understood lateral reflection is the sidewall reflection. It occurs at ear level on the side wall about half way between speaker and listener location. Right speaker is reflected into right ear.

There are two other lateral reflections that are just as important as the side wall reflection. Upper corner and lower corner sidewall reflections arrive a few milliseconds after the wall reflection. An 80 dB direct is followed by 3 side wall reflections within 8 ms, well inside the sound fusion time window.

Best Lateral Reflection Control Devices

Where to Put Them?

  1. Enlist a helper
  2. Obtain a small mirror
  3. Round up a roll of blue painter’s tape
  4. Sit in your “sweet spot” chair
  5. Have the helper move the mirror along the wall
  6. Mark the wall with the tape at the location (on each side) where you see the tweeter from your listening seat
  7. Place the control device centered on the mark, covering about 65% of the wall height (e.g, use a 5′ tall absorber on an 8′ tall wall)
Lateral Reflections 1/3

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