Last week I wrote about the multi-dimensionality of a stereo mix. While that article focused on distinguishing localization from depth, I'll be specifically focusing on localization this week.
As a reminder from the last post, localization is often referred to as "pan," and it describes the placement of a sound in the left to right stereo spectrum. However, the pan position is not the only way to place a sound to the left or right of the listening position.
Another technique for achieving this effect involves the use of short delay times, sometimes referred to as the "Haas Effect." It is so-named after the person who is credited with discovering the technique, but I'll leave that bit of history for the reader to discover on his/her own.
The effect is achieved by duplicating a mono sound and panning each copy to the extreme left and right sides of the spectrum, respectively. Next, you add a delay to either the right or left copy so that one is triggered a little later than the other. The delay amount used is very short, between 1 and 35 milliseconds. You can also avoid duplicating the mono sound if you have a stereo delay on the track, in which case you can choose to delay only one side of stereo spectrum independently from the other. The combined effect is that the sound's perceived localization changes depending on the delay amount chosen.
Before I continue this technical discussion, you may be asking why anyone would want to venture beyond simple panning to achieve left to right spread of sounds. The reason is that panning isn't always ideal, and indeed there are times where none of the pan positions will render an acceptable distribution of instruments in the mix. This is the time when the Haas effect really comes in handy. Since the technique relies on creating small phase changes, we're doing more than just turning one side of the stereo spectrum up and the other one down. Of course, this also comes with the danger of creating phase-related problems when the piece of music is reduced to mono, so be sure to check your mix in mono as you work just to be sure that it still sounds acceptable.
Localizing a sound using this method can create all kinds of interesting effects depending on a few factors, the most obvious being the delay time that you've chosen on one side of the stereo spectrum. Beyond this, you can alter the volume of the delayed copy, but be sure that you don't increase it any more than 10 db louder than the dry copy because this can destroy the illusion of changing the sound's overall position. One last easy trick is to add a low-pass filter to the delayed side, carefully carving off some of the high frequencies. This will serve to downplay the delayed copy, biasing the perceived position toward the dry copy.
I've kept this discussion brief in order to whet your appetite for experimentation. Don't take my word for it, give this stuff a try and let us know what tips and tricks you come up with in the comments section!Sound Localization with the Haas Effect by Nick Maxwell