The popularity of Coincident miking techniques like XY and MS and the existence of coaxial monitors like Genelec’s The Ones are proof, if it were needed, that the timbral shifts caused by time of arrival differences are significant. There are a variety of strategies which can be employed to counter these. Which one you choose depends on why you are experiencing these issues.

Like everything in audio, these issues a best dealt with at source. But as technology develops the point at which you can address issues moves further and further down the production timeline. Two very popular tools, both from Sound Radix, for addressing the phasing issues which can be caused when multiple sounds are combined are Auto Align and Pi.

Although both Auto-Align and Pi strive to optimise the phase correlation between signals, each one solves different phase issues and both use very different techniques.

Auto-Align was designed to fix the Comb-filter effect caused by multi-mic recording of a single source, where the mics are placed at different distances from the sound source. When summed in a mix, the difference in time of arrival to each mic causes a phase shift that varies throughout the frequency range and cannot be fixed using a phase rotator. Auto-Align automatically detects the distance and the delay between the mics and compensates for it with sample accuracy.

Pi, is a multi-channel-aware dynamic phase rotator. It analyzes the tracks in your mix in real-time and constantly rotates their phase to improve phase correlation. Pi minimizes cancellations of overlapping frequencies when they interact with each other.

When Would you Choose Pi or Auto-Align?

Auto-Align is more effective for multi-microphone/DI recordings, and Pi is suitable for general phase optimization of your mix.