What are some common phase issues in mastering and how do you fix them?

1 Check your sources

The first step to avoid phase issues in mastering is to check the quality and compatibility of your source files. Make sure they are recorded and mixed with proper phase alignment and polarity, and that they match the sample rate and bit depth of your mastering project. You can use a phase correlation meter to measure the degree of coherence between the left and right channels of your stereo signal. Ideally, you want a positive value close to +1, indicating a strong mono compatibility and stereo image. If you see a negative value or a lot of fluctuation, it means your signal has phase issues that need to be addressed.

2 Use mid-side processing

One of the most powerful and versatile tools for fixing phase issues in mastering is mid-side processing, which allows you to separate and manipulate the mid (mono) and side (stereo) components of your signal. You can use a mid-side EQ to cut or boost specific frequencies in the mid or side channels, enhancing the clarity and width of your mix. You can also use a mid-side compressor to control the dynamics and balance of the mid or side channels, adding punch and depth to your mix. However, be careful not to overdo it, as too much mid-side processing can create unnatural or exaggerated stereo effects.

3 Align phase with plugins

Another way to fix phase issues in mastering is to use plugins that can align the phase of your signal, either automatically or manually. Some plugins use advanced algorithms to detect and correct phase issues across the frequency spectrum, such as Waves InPhase or Voxengo PHA-979. Other plugins let you adjust the phase of your signal by shifting it in time, either in milliseconds or degrees, such as Sound Radix Pi or MAutoAlign. You can use these plugins on individual tracks or on your master bus, depending on the source and severity of the phase issues.

4 Flip polarity with plugins

Sometimes, the simplest solution to fix phase issues in mastering is to flip the polarity of your signal, either on one channel or on both. This can reverse the phase relationship between the left and right channels, or between the mid and side channels, resulting in a more coherent and balanced signal. You can use plugins that have a polarity switch, such as FabFilter Pro-Q 3 or Brainworx bx_control V2, or you can use a dedicated polarity flip plugin, such as Waves PS22 Stereo Maker or MeldaProduction MUtility. However, be aware that flipping polarity can also introduce new phase issues, so always check your results with your ears and meters.

5 Use mono compatibility check

Finally, one of the best ways to fix phase issues in mastering is to use a mono compatibility check, which can reveal any problems that might occur when your signal is played back on mono systems or devices. You can use a plugin that can switch between mono and stereo modes, such as Brainworx bx_solo or MeldaProduction MStereoScope, or you can use a plugin that can simulate different playback scenarios, such as ToneBoosters TB_Isone or Nugen Audio ISL 2. You can also use a plugin that can collapse your signal to mono below a certain frequency, such as Waves Center or Brainworx bx_subfilter, to ensure a solid low-end foundation. By checking your signal in mono, you can identify and fix any phase issues that might affect the quality and consistency of your master.