What is the Haas Effect in Music?

We don’t talk too much about the scientific, physics side of audio here on Music Guy Mixing. I’d rather give you practical advice and explain how to get a result rather than explain the science behind why it works, interesting though it may be.

The Haas Effect is an exception, however, as understanding how this phenomenon works can help you in your mixing.

What is the Haas Effect?

Dr. Helmut Haas presented a phenomenon in his Ph.D. thesis 1949 which would go on to be know as the Haas Effect.

Also known as the “precedence effect”, Dr. Haas explained that if two sounds are played at roughly 40 ms or less apart, the human ear perceives them as one sound.

This is why it’s also known as the precedence effect, in the sense that one sound takes precedence to the listener’s ear.

40 ms is roughly the minimum amount of time you’d need to place between two sounds so that the human ear can differentiate between them.

How to Use the Haas Effect in Mixing

For our mixing purposes, we can utilize the Haas Effect to give our tracks some added width and thickness, using a delay with a delay time to 40 ms or less.

Going back to the principle of the Haas/precedence effect, using a delay creates that second sound.

When the delay time is set to 40 ms or less, the two sounds merge into one longer, thicker sound to your listener.

Setting the delay time too much longer than this, you’ll begin to hear the separation to where it will feel like a fast slapback effect.

You can use this to dial in some quick width and thickness to any track in your mix.

Simply create an auxiliary/return track (see inserts vs sends) and drop your delay plugin of choice (stock or otherwise) on it. Your settings should be similar to those used in the image above, meaning:

• Delay Time – 40 ms or Less (as the effect states).
• Single Delay, No Feedback.
• 100% Wet (When Used as Send With Aux/Return Track)
• Filter to Taste.

Use the Haas Effect to give your vocal tracks or any tracks some extra width when you need them to stand out a bit more (like during a chorus).

As such, a simple delay with these settings makes for a perfect return track to feature in every one of your mixes.

The Haas Effect in Reverb

I just want to make one more note with the Haas Effect regarding reverbs.

Predelay is a standard feature on reverb plugins. This dictates the amount of time in milliseconds before that reverb plays.

As it relates to the Haas Effect, setting a predelay of 40 ms or greater will make the reverb work like a distant, darker delay as the listener can hear a difference between the dry audio and wet reverb version.

Setting the predelay to a shorter setting can still keep that transient intact, but it will make the reverb sound like it’s part of the same audio. This again adds a thickness, albeit with potentially more size which is a major reason producers use reverb in the first place.

Just something to keep in mind as you’re setting your predelay on your reverbs to achieve a number of different effects!