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Stereo imagery effects

Stereo imagery effects alter a file’s stereo image. Audition includes three effects for altering stereo image: a Center Channel Extractor, Stereo Expander, and Graphic Phase Shifter. The latter is a very esoteric tool that you will likely not need to use when you’re doing typical audio projects, so we’ll cover only the Center Channel Extractor and Stereo Expander. For further information on these effects, refer to the Help files.

Center Channel Extractor

With stereo signals, some sounds are traditionally mixed to center—particularly vocals, bass, and kick drum. Reversing the phase of one channel cancels out any material panned to center while leaving signals panned left and right alone. This is commonly used for karaoke to remove the vocal. By filtering the channel that’s out of phase to emphasize voice frequencies, bass and kick aren’t affected that much.

However, Audition’s Center Channel Extractor is a very sophisticated implementation of this principle that allows for boosting or cutting the center channel, and also includes precise filtering to help avoid applying the effect where it’s not wanted.

  1. Choose File > Open, navigate to the Lesson04 folder, and open the file DeepTechHouse.wav. Don’t start playback yet.
  2. Click an effect insert’s right arrow, and choose Stereo Imagery > Center Channel Extractor.
  3. Turn down the monitoring level, and then load the preset Boost Center Channel Bass.
  4. Start playback and slowly turn up the monitoring level. The bass will be excessively loud, and you’ll need to pull back on the Effects Rack panel’s Output control to around -7dB to avoid distortion.
  5. Pull the Center Channel Level control down all the way, and the bass will essentially disappear.
  6. Return the Center Channel Level control to 0. Pull the Side Channel Levels control down all the way to isolate the bass.

The next lesson isolates vocals.

  1. Choose File > Close. Don’t save any changes.
  2. Choose File > Open, navigate to the Lesson04 folder, and open the file ContinentalDrift.wav. Don’t start playback yet.
  3. Click an effect insert’s right arrow, and choose Stereo Imagery > Center Channel Extractor.
  4. Load the preset Vocal Remove. Start playback around 32 seconds. The lead vocals extend to about 47 seconds, but you won’t hear them because they’re being removed (around 45 seconds you’ll hear some backup vocals that aren’t removed because they aren’t panned to center).
  5. Return to around 32 seconds, and start playback. Bring up the Center Channel Level to hear the vocals.
  6. Click the Discrimination tab to access several real-time adjustments. Choose the highest possible Crossover Bleed settings and the lowest possible Phase Discrimination, Amplitude Discrimination, and Amplitude Bandwidth settings that are consistent with sound quality and effectiveness. Increasing the Spectral Decay Rate will often improve sound quality as well.
  7. Leave this file open in preparation for the next lesson.

You’ve now learned the highlights of the Center Channel Extractor; refer to Audition’s Help file for more details.

Stereo Expander

The Stereo Expander is a standalone, and more sophisticated, version of the Widener in the Mastering effects suite. The Stereo Expander has the same goal: expand the stereo image outward to make the difference between the left and right channels more obvious and dramatic. However, unlike the Widener you can also shift the center channel left or right. This lets you “weight” the stereo image more toward the left or right.

  1. Click the Center Channel Extractor effect insert’s right arrow, and choose Stereo Imagery > Stereo Expander.
  2. Start playback. Move the Stereo Expand slider to the left to narrow the image; move it right to widen the image. This effect is most dramatic on headphones, but you’ll hear it on speakers as well. Leave this set to around 150–200 for now.
  3. Move the Center Channel Pan slider left and right. Note how this moves the vocal toward one side of the stereo image or the other. (There are vocals between about 9 and 20 seconds, and 32 and 48 seconds, that are mixed to the center of the stereo image.)
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