In this video, Mo is going to show you should AND shouldn't introduce stereo enhancement whilst mastering. He'll show you how to keep an eye on the phase of your track making sure you stay mono-compatible.
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WHAT CAUSES PHASE ISSUES?
Phase issues can creep into your mix when recording audio using two or more microphones. In a nutshell, this is because the ‘nearly identical’ audio signals induce comb filtering.
This makes the sound weak and thin rather rich and full. Phase issues can also be introduced by certain synth patches and the built-in effects within synths. Different elements of your mix that have overlapping frequencies can also introduce subtle phasing issues.
HOW TO FIX PHASE ISSUES SHOWN BY THE CORRELATION METER?
When the correlation meter heads down towards -1 this shows that the left and right channels are producing opposite audio signals. This can lead to phase cancellation meaning that your mix might sound thin and won't translate well when played back in mono.
Use the MONO button to regularly check your tracks mono compatibility. A good way to reduce phase issues whilst recording is to use the 3:1 rule. Place the second mic three times the distance from the first mic that the first mic is from the source. So, if your first mic is 10 cm for the source of the audio, the second mic should 30cm away from the first mic.
If you're at the mixing stage and can't re-record you can try a phase alignment tool. Alternatively, you can try just nudging the audio a few milliseconds forward or back. Even a small adjustment might have incredibly positive effects on the phase of your mix. Do this whilst listening in mono through one speaker and listen for the sweet spot where the audio stops phasing.
The FILTER in the Stereo Field section allows you to isolate certain frequencies in the master to view their stereo placement. This is useful to see which frequencies are placed more centrally in the mix and which frequencies are placed wider.
Having low frequencies placed very wide in your master can have negative effects on your master. Wide bass frequencies might suffer from phase cancellation when played in mono, making your master sound weak.
Bass also takes up a lot of space, so by keeping it mostly mono, you can utilize the rest of the stereo spectrum for other elements in your mix. When you engage the FILTER (by clicking the ‘FILTER’ button), and you set the high-cut to 250Hz or less, you can see the low frequencies that are too wide glowing yellow and red in the vectorscope.
The goal is to keep the low frequencies in the more central green area. This will lead to a more powerful and balanced master. If you have wide low frequencies, you could try using a stereo placement plugin to place the low frequencies of your master in mono.