Healthy Stereo Width

The art of audio mixing is dynamic. New mixing techniques are introduced and developed as technology develops and musical trends emerge. Stereo imaging has been an important topic since the early 1970s when nearly all monophonic master recordings were converted to stereo. Today's electronic music masters may not be so rich in dynamics. However, they utilize stereo width extensively. Let's look at ways to create a healthy stereo image in our mixes.  

Conventions

Despite the topic's subjective nature, we can use general guidelines when considering the stereo image.  

Widening Conventions

According to commonly accepted belief, the stereo width of a sound should increase with frequency. In other words, low-frequency sounds like sub-bass should be in mono, whereas higher-frequency sounds like white noise should be in stereo.  

Placement Conventions

When talking about stereo width, we also have to consider the placement of a sound in space. In this case, placement refers to a particular channel's "pan" position. For example, prominent elements such as the kick, the sub-bass, the snare, and the vocals should be in dead center. This helps to create a focal point, an anchor that supports the rest of the mix. The background vocals should be around 10 o'clock and 2 o'clock; this helps prevent them from interfering with the main vocal. Anything else, including guitars, synths, and overheads, needs to be far from the center positioning - at least between 9 o'clock and 3 o'clock;  

Widening Techniques

Knowing where sounds should be placed is no real use unless we know how to put them and adjust their stereo image.  

Pseudo Stereo

Pseudo-stereo helps us widen a mono track. We can do this by duplicating the mono track and delaying the clip on one of the tracks by a few milliseconds (long enough to get out of the "phasing" range). Then, pan the two mono channels left and right to give the impression of width without phase issues. This is a mono audio clip:

This is the same clip widened using pseudo-stereo:

 

Mid-Side EQ

This technique differs from the previous in that it is applied to a signal that is already stereo. E caliber is a freeware plugin that enables us to use it. The "mid-side" filter mode enables us to EQ specific areas of the stereo field. "id" passes content in the signal that is identical in both the left and right channels (mono), and "side" passes content that differs between channels. We create this impression of width by decreasing the "mid" frequencies and boosting the "side" frequencies. Here is a mono guitar riff:

Here is this same riff after using mid/side processing in order to widen it.

I exaggerated the effect within Equilibre for demonstration: this is how I set my EQ.

   

Parallel Reverb

Although reverb is not universally considered a widening technique, it is often used to widen a monophonic main vocal track placed in the center of the mix. By sending the track out to a return bus with reverb, the reflections emulate a space and thereby give the sound a certain depth and width (See Blog: Powerful Parallel Processing). This is just one of many applications of this technique. If we take that mono guitar riff from the previous example and add reverb to it on a return bus, this is the result:

Spreading synth across voices

Some synths offer ways of increasing stereo width using native features. They do this by allowing multiple voices to be spread out across the stereo field. Adding some detune between the voices is essential to prevent phase interference. If the voices are similar, they will phase in and out unpredictably. This causes imbalances across the stereo field and may make the sound move right and left (see blog: Phase and Phasing). This is the default patch in Massive with one mono voice:

This is the same patch but with a second voice, the voices panned and detuned.

Here is how the Massive voicing tab looks when the voices are spread:

   

Panning separate recordings

Although this technique involves the placement of sounds in the stereo field more than their width, doubling tracks increases width. This differs from pseudo-stereo because in that it uses two different recordings. For example, we could record the same guitar part twice and pan the consecutive channels right and left, respectively. Since the two parts are recorded in different instances, they won't phase. Yet, since they are both the same riff, it will seem like one very wide guitar part. This can help move the guitar out of the way of vocals and other prominent elements in the center of the stereo image. If we record a second take of the initial guitar riff above and pan each take right and left respectively, we get this:

Now you have the tools to start experimenting with stereo width. Remember, there are a lot of products out there that can help you improve your stereo image, but just as many that can blur and damage it. In the end, any sound engineer will tell you that constructing a healthy stereo image is key to getting a tight overall mix.