What is the Haas Effect?
The Haas effect (properly known as the “Haas Precedence Effect”- there are other unrelated Haas effects) is a way to create a simulate a stereo signal in the studio even when we don’t have a stereo source – or even have access two individual sound sources to start with.
The best way to create a good stereo sound is with multiple takes. This will will provide the best sounding results when you’re looking for a nice, thick stereo sound. Usually in a recording studio we would record two mono takes of an instruments part, put each take on its own track, and pan those tracks left and right. Judicious use of reverb will also help create the sense of space.
However we may want to work from a pre-recording of an instrument or sound and widen the stereo field, in which case recording two takes isn’t an option. Maybe time and resources are limited. For all sorts of reasons two takes might not be a practical option.
How the Haas Precedence effect works.
The Haas Effect is a psycho-acoustic phenomena, resulting from the way our brains work when trying to make sense of the world around us.
If two separate versions of a sound occur in rapid succession – separated by say 5-10 milliseconds, when we hear this our brain “fuses” these two sounds into one.
This merging of the sounds continues to occur until we reach a separation time of about 30 milliseconds, but, when we get to a separation of 50 milliseconds upwards, we will interpret this as two distinctly separate sounds (depending to some extent on what kind of sound we’re talking about). There are some curios things regarding how our brains give priority to the first perceived sound – even ignoring the the second sound, which is covered in detail in research into the the Haas effect and it’s effect on our perception of sounds. For more information have a look at this Wikipedia article about The Precedence Effect.
Using this effect.
What we are really interested in though is that if you take a single audio source, split off a copy to create a second version of it, and delay that second version by about 25 to 40 ms – your brain will still not hear the sound as two distinct sounds, it’s already reinforced and sounding like there’s more than on instrument playing. Now comes the good bit: if you pan the two sounds left and right, your ears and brain will interpret the two sounds as being more spread out, that is a wider sound than the your original single point-source of our original mono sound.
Creating a Haas Precedence stereo effect for SynthEdit.
With these few (stock) modules shown below we can create a simple Haas stereo effect. The values for the Delay2 module are shown on the Fixed Values (Volts) module I find a delay of 40 milliseconds (0.04 V) works well, you don’t want any feed back so this is held at 0 V The Level Adj module on the input is just a buffer.
With the default values on the Width slider you get a progression from a mono signal at 5 V through to a wide stereo image at -5 V.
Note: Due to the delay time inherent in this method of imaging you will probably notice some “phasing” effects between the original and the delayed signal when you reach 50% of the mix. This IS a normal artefact with Haas Precedence widening.
Dual delay Haas stereo effect.
Shown below is a an improved version, with two Delay modules for improved separation along with high pass filters. The two Delay modules have different delay times, 30 milliseconds and 40 milliseconds.
Haas effect with pitch shifter.
Another variation is to add a small pitch shift into one channel along with the delay which add slightly to the amount of separation between the channels.
This also gives the impression that the pitch shifted channel is another separate instrument being played.
You don’t want too much pitch shift, otherwise you can get some unpleasant beating and dissonant effects due to the frequency difference. I found that about 0.02V On the Pitch plug was plenty. It’s also best to enable the Anti-Aliasing option in the properties panel, and increase the Block size to 4096.
