Turn a mono track into rich stereo

Ever wanted to give a lush stereo effect to a mono track? You can resort to using a stereo imaging plugin but the effect can leave a lot to be desired. There is actually a very simple way to turn a mono track into a rich stereo sound in your home studio. You can create the effect with no plugin at all or use a simple delay. This article is going to cover several ways to achieve the sound. Pick the method that is easiest for you!

Haas effect

Though the effect is quite straight forward it has a formal name, the Haas effect. The Haas effect is named after Helmut Haas who formally researched the effect in a paper that was first translated into english in 1949. I have been unable to find the date of original German publication. The effect works only on a mono track. You could sacrifice the left or right channel of a stereo track and apply it to the remaining mono channel. Pan your audio track hard left or hard right. It doesn’t matter which extent you choose but you must pan the track 100% to that side. The sound will be coming out of only one speaker. You then send a copy of the audio signal to the other speaker but delay it slightly. I don’t have a reference to Haas’ original work and most online sources differ slightly, but it seems this delay should be no longer than 25-40 milliseconds. This sounds a bit complex talking about sending audio to one speaker and delaying a copy in the other speaker. It really is quite simple once you break it down. There are a few ways to do this described in order from most simple to most complex.

Haas effect sound samples

  • dry keyboard This is the dry, original keyboard part we were working with. Its timbre is a little drab and doesn’t cut through the mix well.
  • keyboard with Haas effect This is the above sample with the Haas effect applied at 18ms. Sounds much cooler and it sits in the mix really well.

Easy Haas effect

Start with your desired track panned center. Copy the sound file to an adjacent track (it doesn’t strictly have to be an adjacent track but it makes things nicer to look at). You should have something similar to Figure 1.

keyboard copied for haas effect
Figure 1

Now we move one of the tracks back no more than 30 milliseconds. Back in this case means “to the right” which would be the audio equivalent of delay in the signal. You don’t have to move a full 30 milliseconds as shown in Figure 2 but you probably won’t hear the effect very well unless you move at least a few. The more you move the more pronounced the stereo effect will be.

keyboard delayed for haas effect
Figure 2

Almost done. The last thing to do is pan both tracks in opposite directions. It doesn’t matter which direction you pan them. You can put the original on the left with the Haas track on the right, or the other way around. Pick which sounds best for your mix. The main thing is that you pan them 100% and one on each side as shown in Figure 3.

haas effect panning
Figure 3

Have a listen. You should be greeted with a very rich stereo sound similar to my sound samples above. The advantage of this basic way of setting up a Haas effect in your home studio is the simplicity. Most modern DAW programs make this process as easy as: select, copy, paste, drag, pan, done. It can be set up very quickly and you can adjust the amount of the delay by nudging the soundfile back and forth. This way of doing the effect also allows you to easily adjust the delay by very small amounts. Most delay plugins give you resolution in full millisecond steps. By sliding the track manually you can adjust the delay down to the sample (typically one 44-thousandth of a second or more). The main draw to this method is having two copies of the soundfile in your project. If you later decide to edit the part you will not only have to perform the same edit on both tracks, but you will actually have to perform the edit on the Haas track offset from the original edit. This is where the next method comes in…

A better Haas effect set up

Wouldn’t it be nice if both soundfiles could be edited together? This way of setting up the Haas effect allows you to make identical edits in both tracks without worrying about the offset of the delayed track. Start by setting up two tracks with the same soundfile and pan them to opposite sides like we did in the first method (see Figure 1 and Figure 3). The difference in this method is the use of a delay plugin on one track instead of manually sliding it. Most DAW software comes with at least a basic delay plugin and it should be fine for this effect. Your delay plugin needs to be able to do small delay times (1-30ms), and adjust the wet/dry mix ratio with either a wet/dry balance or individual level controls for each.

  • Load the delay plugin on either one of the tracks.
  • Adjust the delay for 100% wet, 0% dry
    • Delay with a wet/dry balance knob: turn the knob all the way to wet
    • Delay with individual wet/dry volumes: set the wet volume all the way up and the dry volume all the way down
  • Set the delay feedback (number of repeats) to minimum (one repeat)
  • Set the delay time to your desired value (1-30ms)

I usually start at about 20 milliseconds and play around from there. This effect makes the delay time very sensitive so you may find a completely different sound at 19ms from the one at 20ms, and yet another new sound at 21ms. Play around. A great advantage of this method is being able to change the sound of the effect by adjusting your delay time up and down without worrying about sliding a soundfile back and forth in the multitrack view of your DAW. It is also easier to remember where you got the cool settings, “It sounded awesome at 18ms” instead of “Now was that cool sound at 235 samples offset or 325 samples offset?” You can also make edits to the soundfile in the same place on both tracks without having to calculate offsets. I can hear you thinking, “What I’d really like is to not duplicate the soundfile at all, and only have to make edits in one place!” Fear not, and read on…

Haas effect advanced routing

Assuming you’ve been following along, lets start where the last example left off. You now have a nice sounding Haas stereo effect happening but you would like to eliminate the duplicate soundfile. Delete the soundfile from the track with the delay plugin on it. Instead, route an auxiliary send from the track with the soundfile to the track with the delay. This send should be pre-fader, pre-pan but is ok to be post effects if you have some other effects on the track (possibly eq or compression). Now you have the Haas effect but you only have one soundfile in your project view. Making edits is no more difficult or involved than for any other non-Haas track (unlike the first two methods we discussed).

The main complexity with this method is how to set up the auxiliary send in your DAW software. Some software like SAWStudio provides a fixed number of sends from which you will need to use one as the delay send for this one track. Software like Sonar offers a bit more flexibility to create new auxiliary send tracks but they still live off on their own section of the mixer. Some software has more advanced routing possibilities to send any track to any other track. Reaper is in this family and allows you to keep your Haas track visibly “next to” the track it is coupled with.

More Haas experimentation

Haas’ original research says the delayed track can differ in volume from the original track by up to 10dB. That means you can adjust the delayed track up to 10dB louder or 10dB softer than the source track. You can get some interesting effects across the stereo field playing with the volume balance of the two tracks. The effect will also generally sound richer through speakers than headphones.

Related article: Creating heavy guitar tracks with haas delay.

Featured plugins: Create haas delay effects without complex routing by using this free VST plugin. A professional version is also available.

Now you know how to turn a boring mono track into a lush stereo sound that jumps out of the speakers. Remember boys and girls, DO try this at home!

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11 Responses to “Turn a mono track into rich stereo”

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  1. Great tip, man!!!
    I was already using it (from scratch, I must say) to record my guitars with the POD X3 Live.
    But the send/insert tip just opened up a hole new dimension to my mixes!
    Try this with your snares with delays of only 7ms to 11ms and you’ll be amazed.

    Your articles are very useful.
    Keep’em coming and rock on.

  2. flmason says:

    Anyone found a way to use this and not have it sound strange if your recording ends up being played on a mono system?

  3. bvesco says:

    You do have to be extremely careful with this effect if your mix is destined to be played back on a mono system. In general a longer (up to 30ms or so) delay setting will offer less problems with mono playback. It is very dependent on your source material though.

  4. alexela says:

    haas rules

    i think around 5ms is the minimum a very trained ear can distinguish… anyone?

  5. alexela says:

    sweet article by the way

  6. bvesco says:

    Thanks.

    And it depends on what you mean by distinguish. If you mean distinguish as two discrete sounds then it is closer to 50-60ms. If you mean hear the effect of delay then it is all the way down to 0.00001ms or so, depending on the frequency content of the source material. High frequencies with the slightest (as in a few samples) delay can cause noticeable comb filtering where low frequencies can have delay up a few milliseconds and you’ll never notice.

    Another key to this effect is that the sound sources come from two different speakers so you have no basis for comparison. We’re talking about the same amount of delay as having a conversation from opposite ends of a dinner table. Did you ever look at your dining partner and think their words didn’t sync with their mouth?

  7. Steve says:

    bvesco does has a point.
    On your mixer it may be interesting to check your final setting in mono.
    I’m sure you’ll find the tone changes. This probably is not an issue if above 20ms. Low delay times less than 10ms may create a flange type effect without the sweep. It could make it nasal sounding.

    Having said that, this effect has been used for years. The tone NOT delayed will “appear” to be louder making it seem as if panned more to the non-delayed side.

  8. Marlon says:

    I use the duplicate track and move it method all the time. However, I usually move it no more than 10 ms to the left (instead of 30 to the right), detune the reverse-delayed track by about 10 cents, flip the phase of that track, and pan them hard left and right.

  9. J.Vance says:

    Well… doing a trick like this (panning two mono-tracks 100% left and right and delaying right track), you shift your sound to the left side.Your stereoanalyzer won’t warn you, because it reacts only on energy levels, but human brain uses delay between two channel (two ears) as dimensional cue.
    If you decrease level of delayed signal by 10 dB, this pan shift will naturally become more obvoius. This is actually a method used for “true stereo” panning – you pan signal to the left (increase volume level in this channel) and simultaneously add small delay to the right channel.
    You can, on the contrary, increase level on delayed track, but this will not give you natural stereo effect.
    You can easy do this trick in Sonar with just one mono track in “stereo” mode, using Channel Tools plugin

  10. Certainly not an easy thing to do correctly without getting phase problems of somekind. Nicely explained cheers. Very important to check the stereo image by ear and if you are not sure with a phase correlation meter.