Although you can get away with using delay-based stereo imagers on an individual instrument once in a way, you should typically avoid them due to the phase cancellation that they cause. Granted phase cancellation will always come into play when widening the image, but certain expanders cause more artifacts.
This is especially true when it comes to your mix bus or master, where you should almost never use a delay-based stereo imager.
Let’s take a listen to one being used on mix bus, and notice how the mix becomes washed out.
A safer way to expand your stereo image is to use a left-right EQ and create 2 bells, one on the left and one on the right. Then vary their frequencies slightly - this will cause the left and right channels to be louder but at different frequencies.
As a result, the image sounds wider, but without too many artifacts or unwanted phase cancellations.
Let’s take a listen and notice how this sounds much cleaner than chapter 1’s demonstration.
Similar to our last chapter you can use a mid-side EQ to expand the stereo image - you can pick which frequencies you’d like to expand and amplify them on the side image or attenuate them on the mid image. A high shelf on the side image works well.
Or say I want to process on the vocal to come through a bit more, but I only have the stereo mix, I can increase roughly 2kHz on the side image with a bell.
Let’s take a listen to these 2 filters being added to our mix bus.
When mixing, if you create 2 identical signals, you can use an EQ on one to cause natural-sounding stereo placement. So say I want my guitar to be on the left - I can duplicate it, pan the 2 tracks hard left and right, then EQ one.
For our example, I’ll use a high-pass filter on the right guitar, making the guitar’s lows sound as they’re on the left. By duplicating and panning left and right, we basically have a mono signal since everything is identical - but making this change to the frequency response will shift the perceived placement.
If we have a mid-side saturator, we can saturate either the mid or side to add more signal to one or the other - this creates a more centered or expanded image respectively. For example, I’ll saturate the mids, and pan the saturation to the side to make them wider.
Since the saturation isn’t always happening, this expansion will be program-dependent as well.
Let’s take a listen and notice how the subtle expansion is dynamic.
If our saturator offers modulation, we take this a step further by linking an oscillator or envelope to our panning or a drive function. For example, I’ll create an envelope follower, and attach it to the drive functions panning - so that when we get a transient, the harmonics are panned.
Similar to before, we get dynamic saturation - but this way we have more control over the behavior of the saturator.
Let’s listen to this example, and consider how it’s different than the previous example.
If our left-right or mid-side EQ offers dynamic processing, we can use it to make our expansion program dependent. So, let’s create some of the same bands that we used in chapters 2 and 3, but this time, make them dynamic and increase their ranges to expand the bands.
We’ll notice that the expansion is now contingent upon the incoming signal - in turn linking the dynamics of the track and the stereo expansion.
Let’s take a listen and notice how it varies from the demonstrations in chapters 2 and 3.
If a compressor or limiter offers mid-side compression or limiting, we can use it to dynamically expand the stereo image. The reason is, the most powerful signals, like the kick and bass, will typically be in the mid image - causing more compression to the mid than the side.
As a result, whenever the kick or bass hits, the mid will be compressed, leaving the side at a louder level comparatively. This isn’t the best technique for retaining dynamics, but it works well at stereo expansion.
Let’s take a listen.
A common question is whether or not the lows should be made mono, or kept stereo. On one hand, you get a more driving low range and reduce phase cancellation, on the other you may lose some of what makes the mix unique.
You can use a high-pass on the side image to cut the lows from the side, and from there determine the cut-off. As you’d imagine, this will reduce the width, but it can have a very beneficial effect on your mix.
Let’s take a listen to the lows being made mono up to about 100Hz.
One challenge with stereo expansion is making the side image more detailed since a lot of softer elements are on the side. One solution is to duplicate the signal, use the free plugin MSED on both, and isolate the mid on one channel and the side on the other.
Then place a transient expander on the side imaged signal. This is a bit unorthodox, but it has a cool effect that’s difficult to achieve otherwise.
Let’s take a listen to it and notice how much detail we can get on the side.
Similar to our last tip, we can use this same MSED plugin to separate our signals, and then use any form of processing discussed before to process our mid and side separately. So, say we don’t have a mid-side EQ, now we could simply EQ the side channel.
The same could be said about compression, expansion, or any other form of processing. Let’s listen to mid-side equalization, but use an analog emulated plugin on the side channel that normally wouldn’t offer mid-side processing.
Let’s listen and notice how we expand the stereo image.