Haas Effect (psychoacoustics)

Try listening to all your songs in both mono and stereo and consider what sounds better. Most times, the stereo will sound significantly better. Each sound and instrument can occupy it's own space somewhere from left to right

The main way to place a sound is to pan it, where you change the volume of that sound in each speaker e.g, if you want the guitar to the left, you make it louder in the left ear and quieter in the right. This feature is common across most mixers and is the easiest way to move the "position" of the sound.

Another way uses psychoacoustics. Sound takes time to travel through the air if it comes from the left, it will hit your left ear a fraction of a second earlier than your right ear. This is still perceived as one sound but your brain is able to interpret the direction it is coming from. And so the Haas effect replicates this by delaying the signal in one ear by a small amount.

Here is an example of the mono signal followed by it with the Haas effect on it:

You can hear how there is no volume difference on each side but it is certainly a directional sound. So what is an easy way to do this? If you are uncomfortable replicating it yourself there is an easy VST plugin that will do it for you, just chuck it onto the FX chain at a suitable position and dial in the amount of milliseconds to delay one side. It is very simple and can be downloaded HERE.