Stereo Field & Spatial Effects
The Haas effect: a 10–30ms delay on one side creates perceived width without changing volume. Mid/side encoding separates center from sides.
Stereo from Mono
A mono signal sits in the exact centre of the stereo field, identical signal in both ears. To move it sideways, we change the balance between left and right channels. Panning uses an equal-power law (cosine/sine curves) so the sound stays the same perceived loudness whether centred or hard-panned. But panning alone only narrows the image; to make a mono source sound wide, we need something more.
The Haas Effect
If one ear hears a sound 10–30 milliseconds before the other, our brain perceives a single source shifted toward the earlier ear, without hearing a distinct echo. This is the Haas effect (also called the precedence effect). By delaying one stereo channel by a few milliseconds, we trick the brain into hearing width from a single mono source.
Mid/Side
Mid is the sum of left and right (the centre image). Side is the difference (everything panned away from centre). By processing them separately (boosting sides for width, or cutting sides for mono compatibility) you can reshape the stereo field without touching the source.
Try it: start with "Center" and slowly increase Width. Listen on headphones to hear the Haas effect open the image sideways. Then try "Mid/Side Boost" to hear the sides emphasised.