The Haas Effect
The Haas effect or the Precedence Effect is a Psychoacoustic Effect described by Helmut Haas as the ability of our ears to localize sounds coming from anywhere around us.
In short, our ears determine the position of a sound based on which ear perceives it first and its successive reflections (arriving within 1-35 ms from the initial sound) which, will give us the perception of depth and spaciousness. Pretty simple!
In general, we use our pan knobs to position sounds within the stereo field. Lets discuss panning briefly… If we have a sound coming out of a stereo pair of speakers at an equal volume, our ears will interpret that the sound is coming out from the middle. So, panning is not much more than the amount of volume you send to each speaker… Let’s remember that our ears depend on not only volume, but also on time and frequency differences for the localization of sounds.
The Haas Effect – How To
The concept of the Haas effect can be applied in order to get a wide, open and spacious sound resulting in a more realistic sense of depth. In our example, we’ll use a stereo-delay plug-in to achieve this effect. There are 3 things to remember:
1) Set the delay time on the side where you want to perceive the sound is coming from to ‘0’ (no delay)
2) Set the delay time on the opposite side anywhere from 1 ms – 35 ms. Solo your track and increase the delay time starting from ‘0’ and listen!
3) Watch for a possible loudness increase since you are converting your mono track into a stereo track when you insert the stereo delay plug-in. My suggestion would be to set the ‘MIX’ control on both sides of the stereo-delay to 50%. Adjust your track volume accordingly.
The Haas Effect – Example
Listen to the following audio examples using the Haas effect technique in two mono guitar parts.
Both guitars panned center:
Guitars panned L50-R50:
Haas effect concept; a stereo delay plug-in is inserted on each guitar track. See pictures for settings. Notice that the settings are exactly the same but applied accordingly (inverted) on each side.
As with anything in mixing, experiment using different settings and tweak different parameters until you get the desired results. Choose only one or two instruments that you feel should sound open and spacious and apply this technique. Overuse could result in an unfocused stereo image.