Zen and the Art of a Strong Stereo Image
This is a guest post from mastering engineer Barry Gardner who operates SafeandSound online mastering
From time to time I hear a mix that has a dubious stereo image. This can affect both acoustic or electronic mixes.
For acoustic mixes it is often the mic technique that creates a problematic stereo image. For electronic mixes, there are a variety of reasons why bad stereo imaging occurs.
By dubious I mean the stereo image does not have the traits of a professional mix-down. It may be too narrow with many monophonic sources or it might be too wide sounding with possible phase problems, e.g. not mono compatible. This can be due to over use of stereo width enhancers or it may suffer from blanket application of effects across multiple mix tracks.
Make Sure It Works in Mono
When you mix your track it is important to mono the track and make sure that the track does not sound excessively different in mono.
It should maintain a similar tonal balance in mono with some sources even sounding slightly louder. If you have a serious phase issue for any sources they will tend to lose bass or drop significantly in level when summed in mono. At worst, they’ll vanish from the mix entirely. So make it a habit to check your mix in mono as it builds.
In some instances there may be a single stereo source that is out of phase between the channels and goes unnoticed. We all want to have wide, punchy sounding mixes and this can be a challenge for the beginning engineer.
After all, there are many technical aspects to learn when you’re first starting out. One common issue I have found is the application of a single effect across multiple mix tracks. Reverb is the most common stereo enhancing effect in people’s mixes. I would like to take the stereo image aspect of mixing back to the starting point and look at the sound selection. (drum hits, samples, synths, vocals, effect sweeps and other elements that make up your music)
In many instances people tend to start their track by picking sources that they like the sound of. There’s nothing inherently wrong with this, it’s what we all do. However, it is worth introducing another layer of selectivity when you choose your sound sources.
A Stereo Image for the Electronic Musician
For electronic musicians it is important to understand whether your source samples and sounds are monophonic or stereo. If they are mono they will have exactly the same information in the left and right channels and if they are stereo they will have a sense of space.
If you are unsure. try mono-ing some sources in your DAW and see if the stereo image changes. If there is no change then the source is mono but if the source loses some depth and space then it is highly likely to be stereo.
The reason I suggest this is so that from the outset you will be building an appropriate stereo perspective into your music. Sounds that are commonly stereo (the technically correct term being pseudo-stereo) would be synth patches (pads, leads and some basses), synthetic snare drums, sweeper effects. Sounds that may more commonly be mono may be kick drums and instrumental samples. There is no hard and fast rule so use the mono-ing technique above to find out if the sources are mono or stereo. Doing this results in less problems with phase as you will be avoiding these pseudo-stereo creating techniques.
Avoid the Unnatural
One of the most unpleasant techniques some people use to artificially enhance the stereo image is to put a short stereo reverb on all the drums, the synths and bass line which are all from mono source samples. This produces a slight sense of extra depth. However it also produces an unnatural and unpleasant global coloration to all the sources and has a somewhat “cheap” and subtly metallic sound to the mix. So from the outset, pay attention to your choice of sounds when you are building the track.
If you want to create a pseudo stereo image for a specific mono source, you can use a few different techniques. In fact adding a little reverb is perfectly OK, but limit it to one sound source and don’t apply the same reverb to every single source you have.
- You may wish to double up the mono source on 2 channels, pan hard left and right and delay one side by a few milliseconds. (always double checking mono compatibility by mono summing or checking on a correlation meter)
- You can add a subtle stereo based delay to a sound which can widen the sound (often a subtle ping pong with hard left panned delays can do the trick).
- Another technique is to double 2 mono sources panned hard left and right and apply two separate digital graphic EQ plug-ins. Create opposing EQ boosts and cuts to each signal so they don’t have the same sounds. At any given frequency the left channel gets a boost and the right gets a cut through all the available bands.
Stereo imaging enhancers rely on already available stereo information in a source. By all means use them sparingly to assist width creation but be aware in over-use since mono compatibility may fail. All these enhancements can be used with care and in moderation with actual stereo sources to give a deeper and wider mix sound. Also, do not be afraid to leave a mono source strictly mono as it all adds to fill the stereo image in a natural way.
Know Your Sources
As well as sources that are very narrow it is worth being vigilant towards overly wide sources.
For example, many factory synth patches are created to sound big wide and lush. In some instances this is overdone and when summed to mono they can sound very different. In such instances, knowing how to program your favorite synthesizer comes in handy.
When these techniques are applied with care and respect to mono compatibility, they should produce a fuller, stable, mono compatible and more euphonic stereo image for your mixes.
None of these pseudo stereo image enhancing techniques replace good source selection stereo imaging.
It is highly recommended that all experiments are checked for mono compatibility either through mono summing your stereo bus or checking on a freeware phase scope like “Flux stereo tool” or “Voxengo Span”. Selecting from a wide palette of sound sources helps bring a natural depth and separation to your mix-down.
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Image by: pittaya