Creating a Haas effect

The Haas effect, or precedence effect, or law of the first wavefront, is a phenomenon discovered by Helmut Haas. It says that delays shorter than 25-35ms tend to sound fused with the direct sound.1

Shorter delays, below 10ms, are most useful. At 1ms, there’s a cut at 500Hz, a boost at 1kHz, a cut at 1.5kHz, a boost at 2kHz, etc.2 At .5ms, this all shifts up an octave. At 2ms, it shifts down an octave.

Hard pan the dry and delayed signal and check correlation of a specific delay time. You can be intentional about which frequencies you’d like to comb out. Use EQ or phase correction to correct any unwanted comb-filtering.

This is also useful for delays with slightly different left and right channel delay times.3

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