I recently had a conversation with a friend in which I introduced him to the “out-of-speakers” trick as it was presented to me in Mixing Audio (Izhaki, 2012).  I think, of all things I learned in my Music Production degree, this was the most surprising.  Maybe this trick has been used on me before, but the manner in which the out-of-speakers trick is applied in the audio files accompanying the book jumps out at a person, or rather into a person.  I’ve never heard such a stark example; I perceive the sound as inside my head or wrapping around.

Perhaps in professional circles the out-of-speakers trick is a mere parlor trick or gimmick, but to a student it was intriguing.  It also makes for great conversation when someone sits in front of my studio monitors and I give them a listen to the effect.  The ensuing conversation most often begins with astonishment.

My friend, intrigued by the example from the book, is excited to apply the trick in one of his own mixes.  He is on a short business trip, so has only his headphones to work with.  Unfortunately, the trick won’t work in headphones because it depends on spatial perception; the way we hear signals arriving at our ears at different times depending on the location of the source.

When listening on headphones, both the left and right ears are fed exclusively with the corresponding channel. This means that the left-channel signal reaches the left ear only, and the right-channel signal reaches the right ear only. With speakers, however, this is not the case. Sound from each speaker reaches the nearest ear first and the farther ear soon after. Effectively, each ear gets the signal from the nearest speaker blended with the slightly delayed signal from the other speaker.

(Izhaki, 2012)

So my friend can apply the technique to his mix, but will have to wait until he is in front of his monitors again to hear the result.  Following is the process and an example:

  1. Copy a MONO signal to a second track.
  2. Pan the original MONO signal hard to one side.
  3. Pan the “ghost” copy on the second track hard to the opposite side.
  4. Phase invert one side (the two tracks 180° out from the each other).  In Logic Pro this can be done in the Gain plugin.
  5. Experiment with boosting gain on the phase-inverted track.  This is not always useful on all instruments and the more boost the more the effect may be negated

This example switches every 2 bars between a normal, center-panned stereo image and using the out-of-speakers trick.

I found the binaural panning in Apple’s Logic Pro to also have some intriguing effect, but that is another article.

A warning:  this effect can cause strange behaviors in your mix, so you really have to pay attention to what happens, both when the treated tracks are isolated and in the mix.  Because these two tracks are exact copies and out of phase, they will cancel each other when folded to mono.  This may occur not only at the output, but also at any send in which both are sent.

Works Cited

Izhaki, R. (2012). Mixing Audio (2nd Edition ed.). Kidlington, Oxfordshire, Great Britain: Focal Press.