The Haas/precedence effect is an effective psychoacoustic phenomenon that we can simulate for a greater sense of space in our mixes. If you're interested in learning more about it and how to take full advantage, you've come to the right place.
What is the Haas/precedence effect? The precedence effect (aka Haas effect) is a psychoacoustic effect having to do with sound localization. It states that slightly delayed sounds (early reflections, echoes, etc., less than 40 ms) are perceived as a single sound, with the directionality being that of the first-heard sound.
In this article, we'll discuss the Haas/precedence effect in more detail and investigate how we can go about using it to our advantage in our mixes.
What Is The Haas/Precedence Effect?
The precedence or Haas effect is a binaural psychoacoustic effect, meaning it has to do with how we naturally hear the directionality of sound in the real world.
More specifically, it states that when two identical or sufficiently similar sounds are heard in fast succession, they will be heard as a single sound. The first-arriving sound will largely define the perceived direction of this sound.
“Sufficiently similar sounds” generally means early reflections in an acoustic environment.
“Fast succession” generally means a delay below 40 milliseconds, though this time may be shorter for more transient, higher-frequency sounds (clicks, for example).
So, slightly delayed sounds are perceived as a single sound, and the perceived direction of the sound is dependent on the perceived location of the first heard sound, nearly regardless of the direction of the second.
Haas Wallach, a German-American psychologist, carried out experiments regarding the effect in 1949, naming it the “precedence effect”.
The Haas effect will hold up even when the second sound to reach the ears is louder than the first (up to about 10 dB louder).
The precedence effect is useful in nature, as it helps us locate direct sounds more definitively, even when there are relatively high-level initial reflections.
Mixing With The Haas/Precedence Effect
When it comes to mixing, the Haas effect can be used to widen a sound, giving it a greater sense of spaciousness without it being heard as its own distinct echo.
Although the exact delay times vary by the frequency content of the sound/audio, it's generally accepted that two identical (or very similar) sounds heard within 40 ms of each other will be interpreted by our brains as a single sound.
Transient sounds will have a lower “echo threshold”, where delay times below 40 ms are often heard as two distinct sounds.
The precedence effect can be used to widen a sound in the mix and balance the stereo field without compromising a track's perceived direction.
Let's consider a few different ways of going about utilizing the Haas effect in our mixes.
Displacing Audio To Achieve The Haas Effect
Perhaps the most straightforward way to utilize the Haas effect in our mixes is to duplicate a track, shift the timing/phase of the copy, and pan the two appropriately.
We can opt to hard pan two copies of the same signal and delay one slightly for a super-wide effect. Alternatively, we can go narrower in the stereo field or even to varying positions of a given stereo direction (left or right).
Whichever track's audio happens first will dictate the overall perceived direction of the sound.
Using Short Delay To Achieve The Haas Effect
We can also opt to use a delay plugin if that plugin offers sufficiently short delay times. Ensure your delay offers delay times below the echo threshold. Remember the 40 ms rule of thumb.
Be sure to set up a proper auxiliary effects return to have independent pan control over the original sound and the delayed sound. Send audio from the original track to the effects return and pan the two tracks appropriately.
I discuss how to use effects sends/returns and the benefits of doing so in the following YouTube video:
For more info on auxiliary tracks, check out my article Mixing/Recording: What Are Auxiliary Tracks, Sends & Returns?
Using Dedicated Haas Effect Plugins To Achieve The Haas Effect
There are also plenty of plugins that offer some sort of Haas-style effect. While this is often an additional “stereo” control on a more complex/capable plugin, a few dedicated plugins are worth mentioning.
The Venn Audio Quick Haas (link to check it out at Venn Audio) is a free option, available as a Windows VST or Mac VST or AU.
The Kilohearts Haas (link to check it out at Kilohearts) is another great free option that can be used as regular plugins in your DAW or loaded as Snapins in any Kilohearts Snapin Host.
Back To Mixing With The Haas/Precedence Effect
Note that utilizing the precedence effect will cause phase issues that will effectively take the form of comb filtering. This may not be overly noticeable when the dry and wet signals are panned apart. However, it's important to check the mix in mono to ensure the comb filtering isn't too destructive to the tracks and the overall mix.
I have a video going into detail about the importance of mono compatibility. Check it out here:
For more information on mono compatibility, check out my article Mixing: What Is Mono Compatibility & Why Is It Important?
The Haas effect also tends to push elements further back in the mix, which is something else to be aware of when utilizing the effect.
Although the Haas effect will hold up even when the second sound to reach the ears is louder than the first (up to about 10 dB louder), it's generally advisable to mix the delayed signal lower to help avoid the aforementioned issues of comb filtering and depth.
Using the Haas effect can help to fill out the stereo spectrum of a sparser mix without having a massive effect on the intended direction of the original source.
It's also generally much less potent than using longer delay times or reverb, which may lead to unwanted washing out of certain elements in the mix (and the mix in general). With the Haas effect, we can get a sense of directionality and width without the typical downsides of these other time-based effects.
Be sure to check out my top tips for width in the mix in this YouTube video.
Many great mixes have a natural sound to them, as in they sound like the listener is in the room with the musicians. Other mixes sound great but aren't exactly realistic-sounding.
Regardless of the mix aesthetic, it's worth understanding the basics of psychoacoustics (how we naturally hear sound) to make better mix decisions. The Haas/precedence effect is no exception.
Try utilizing the Haas effect in your mixes to give them a greater sense of dimensionality. Experiment with delay, reverb, and timing differences between audio tracks to achieve the effect.