Originally Web posted 1 June 1997.
Content last modified 21 June 1999.

Adjusting Head Azimuth by Ear

As submitted to Radio World

I would like to expand upon the fine suggestions made in Bruce and Jenny Bartlett’s article Set Azimuth without using Tones (Radio World 24 August 1994).

Listening for phasing effects works quite well for stereo tapes as well as mono, assuming the stereo signal contains a significant amount of center information, which it usually does. I use the following procedure:

  1. Find the program segment with the most high-frequency-rich center information.
  2. Adjust azimuth for clearest high frequency reproduction in stereo.
  3. Switch the monitor system to mono, and fine-tune for clearest highs.
  4. Switch repeatedly between stereo & mono. Other than image collapse in mono, the sound quality, especially at high frequencies, should not change. If the sound is more muffled or “phasey” in mono, you’re probably on a false peak. Repeat 2 & 3 until correct.

Although less accurate than the listening method, a Lissajous display can sometimes be useful with a stereo tape:

  1. Find the program segment with the most high-frequency-rich center information. Strive to find an isolated cymbal, sibilant-rich voice, or other high-frequency source.
  2. Adjust azimuth (in stereo) for narrowest stereo “cloud” (closest approximation to a 45° line). Minimize 135° high frequency bursts, especially sibilants.

These methods, especially the listening method, have proven quite effective, especially with the ubiquitous compact audio cassette. The listening method has been used by volunteer staffers at KALX for over 8 years with excellent results (especially since the Production Studio Nakamichi 482 cassette deck was modified for tool-free play head azimuth adjustment).

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