Have you ever recorded a band with one guitarist and wanted to widen the stereo image to fit more elements of a mix? Perhaps you just want to ad an element to you vocals and don't have time to multi track? Consider using the Haas effect for this and much more!
Named after Helmut Haas who first described it in 1949, the principle behind the Haas Effect can be used to create an illusion of spacious stereo width starting with just a single mono source.
Haas was actually studying how our ears interpret the relationship between originating sounds and their ‘early reflections’ within a space, and came to the conclusion that as long as the early reflections (and also for our purposes, identical copies of the original sound) were heard less than 35ms after and at a level no greater than 10dB louder than the original, the two discreet sounds were interpreted as one sound. The directivity of the original sound would be essentially preserved, but because of the subtle phase difference the early reflections/delayed copy would add extra spatial presence to the perceived sound.
Effect Panning
So in a musical context, if you want to thicken up and/or spread out distorted guitars for example, or any other mono sound source, it’s a good trick to duplicate the part, pan the original to extreme right or left and pan the copy to the opposite extreme. Then delay the copy by between about 10-35ms (every application will want a slightly different amount within this range), either by shifting the part back on the DAW timeline or by inserting a basic delay plugin on the copy channel with the appropriate delay time dialled in. This tricks the brain into perceiving fantastic width and space, while of course also leaving the centre completely clear for other instruments.
You can also use this technique when all you really want to achieve is panning a mono signal away from the busy centre to avoid masking from other instruments, but at the same time you don’t want to unbalance the mix by panning to one side or the other only. The answer: Haas it up and pan that mono signal both ways.
Of course there’s also nothing stopping you delaying slightly one side of a real stereo sound, for example if you wanted to spread your ethereal synth pad to epic proportions. Just be aware you will also be making it that much more ‘unfocused’ as well, but for pads and background guitars this is often entirely appropriate.
As you play with the delay time setting you’ll notice that if it’s too short you get a pretty nasty out-of-phase sound; too long and the illusion is broken, as you start to hear two distinct and separate sounds – not what you want here. Somewhere in between it’ll be just right and you’ll find just the space you want. Also be aware that the shorter the delay time used, the more susceptible the sound will be to unwanted comb filtering when the channels are summed to mono – something to consider if you’re making music primarily for clubs, radio or other mono playback environments.
You’ll probably also want to tweak the levels of each side relative to each other, to maintain the right balance in the mix and the desired general left-right balance within the stereo spectrum.
There are many different ways you could use this technique either from a mix perspective or sound design to give extra depth to a track or effect. be sure to check out some of the links below with more information regarding this topic.
AudioSchoolOnline. (2017, October 09). Mixing Tip - The HAAS Effect - Audio School Online - Ken Lewis.
Retrieved from https://www.youtube.com/watchv=MvSfXHudhTIFitzpatrick
D. C., Kuwada, S., Kim, D. O., Parham, K., & Batra, R. (1999). Responses of neurons to click-pairs as simulated echoes: Auditory nerve to auditory cortex. The Journal of the Acoustical Society of America, 106(6), 3460-3472. doi:10.1121/1.428199
McAllister, M., & James, B. (2018, August 20). Haas Effect: What It Is and How It's Used. Retrieved from https://producelikeapro.com/blog/haas-effect/
Tyler, M. (2012, February). Haas Effect.
Retrieved from https://edmproduction.fandom.com/wiki/Haas_EffectWallach,
Hans, Newman, Edwin, B., Rosenzweig, & Mark, R. (1973, December 01). The Precedence Effect in Sound Localization (Tutorial Reprint).
Retrieved from http://www.aes.org/e-lib/browse.cfm?elib=10299
Ward, K. (2011). Creating depth: The Haas effect.
Retrieved from https://mixcoach.com/creating-depth-the-haas-effect-2/
Wikipedia. (2018, September 21). Precedence effect.
Retrieved from https://en.wikipedia.org/wiki/Precedence_effect