JUNE 20, 2024

Sound Radix Auto-Align and Auto-Align Post ARA 2 Support

Sound radix

Pro Tools 2024.6 introduces ARA 2 support for Sound Radix Auto-Align 2 and Auto-Align Post 2, enabling you to use these industry-leading plugins significantly faster and easier in Pro Tools without having to roundtrip audio. A 60-day trial of Auto-Align 2 is included with all versions of Pro Tools (Artist, Studio, Ultimate, Trial, and Intro) to try out—you can download the trial through Avid Link or find it in your Avid Account. Let’s dive into these two solutions in detail and the challenges that they address.

Phase is an elusive and often misunderstood subject, frequently cited as a key differentiator between professional engineers and amateurs. That is, of course, a gross exaggeration. Still, it illustrates how vital yet intricate the subject is. This is mainly because phase issues become audible only in relation to another signal. For instance, a microphone with inverted polarity may sound fine in isolation. However, when paired with a secondary mic pointed at the same source, discrepancies emerge.

Despite the wide variety of phase-related issues and their solutions, they're often simplistically labeled as ‘phase issues’. This often leads to adopting a ‘dice-throw’ approach (“Just click the phase button”), potentially causing more harm than good.

To help you lift the hovering mist, we overview the three main types of ‘phase issues’, offer the best solution for each, and outline the use cases and features of Auto-Align 2, Auto-Align Post 2, and Pi.

Let’s unphase the haze!


When taking two sine waves at the same frequency and level, you can flip the polarity of one of them and end up with absolute silence. That’s cool, but as you know, the stuff we record is exponentially more complex than a sine wave.

Activating the polarity switch on the mic preamp or console effectively aligns the polarity of vintage microphones produced before the establishment of the standard using pin 2 for the positive polarity terminal of an XLR connection. It is also effective when pointing two mics from opposite sides toward a sound-generating membrane, such as a loudspeaker or snare drum, where air compression and expansion occur in opposite directions on each side of the membrane.

For other use cases, flipping a mic’s polarity may help bring back some canceled-out frequencies while canceling others, potentially causing more harm than good. But frequency cancellations are only part of the story.


With enough sine waves at different frequencies, levels, and envelopes, we can theoretically reproduce any acoustic or synthetic sound. You may be familiar with Additive Synthesis, which is based on this concept.

To illustrate, consider a complex sound composed of two one-second-long oscillating sine waves. The first wave has a fundamental frequency of 110 Hz (A2), and the second wave has a harmonic frequency of 220 Hz. We’ll place two microphones pointing at the source - the first one right at the source and the second microphone at a distance of 1.5 meters.

Let’s take a little break from our story for some hard, cold info:

  • A 110 Hz wavelength is ~3 meters (rounded).
  • A 220 Hz wavelength is ~1.5 meters or ½ the length of our 110 Hz.
  • The speed of sound in dry air at a temperature of 20º Celsius is 343 meters per second.
  • The speed of sound is equal in all frequencies.
  • At this speed, The time it’ll take our sound to reach our distant mic will be ~5ms.

Now that we’ve set the stage, let’s dive in.

By the time our sound wave reached the second microphone, our fundamental 110 Hz frequency had just completed half of its cycle, and our 220 Hz harmonic had completed one cycle.

Assuming we did a good job matching the levels of both mics, when we sum them together, we’ll completely lose our fundamental frequency, and our 220 Hz harmonic would be twice as loud.

Mic polarity
For this case scenario, flipping the phase polarity would bring back our fundamental frequency but make the 220 Hz disappear.
Mic polarity flipped

Maybe we didn’t place our distant mic in a good spot? Actually, any distance we may choose will cause a pattern of boosting some frequencies and attenuating others. This destructive and constructive interference is known as comb-filter.

Other than frequency cancellations, another side effect of the delay between the mics is called transient smearing.
Think of it as a film projector whose colors are misaligned. While it could have a nice effect when used creatively, you should avoid it to experience the true colors and depth of the original film.

Therefore, the best solution to fix this issue would be to compensate for the delay between the microphones and align them in time. It can be done by either measuring the delay between the mics and manually applying a correction or by using a plugin such as Auto-Align, which can sample-accurately detect and compensate for the delay and phase polarity between the mics automatically.

However, what should we do in the case of a film set shooting, where the distance between the boom microphone and the actors’ lav mic varies constantly? A significantly more complex solution is required. One that will be capable of continuously measuring and adaptively applying a sample-accurate delay correction, compressing and expanding time transparently. Enter Auto-Align Post.

But the comb-filter effect is not the end of the story.

In any audio session, different instruments, effects, and layers often occupy similar frequency ranges, particularly in the lower frequencies where longer wavelengths cause more overlap. This interaction can lead to disruptive phase issues and frequency cancellations, diminishing the overall depth of the mix. To address this, we needed a tool that adaptively adjusts each channel's phase. Pi automatically rotates the phase of every track, ensuring they interact constructively and enhancing the overall punch and richness of your mixes.


We can also describe phase shift as a positive or negative delay of a given frequency. For example, a positive delay of a quarter-frequency cycle can be expressed as a 90º phase shift.

This is important because electronic filters, like a High-Pass Filter (HPF) on your mic or pre-amp, naturally induce a phase shift to a variable degree across the frequency range.

If only one of our mics had its HPF engaged, or the filters were set at a different frequency or made of a different design, we’ll get a mismatch in their spectral phase correlation, even though we time-aligned the microphones.

Bring on the Phase Rotator.

A phase rotator is a circuit built using an all-pass filter. This means it doesn’t change the frequencies’ levels; instead, it changes the phase relationship between them. It’s like an EQ, albeit without the frequency balancing effect.

Figure 3 shows the different phasing of the frequencies of a recording, while Figure 4 shows the corrected phasing.

Auto-Align phase problems
Shot Auto-Align Post w/phase problems
Auto-Align Post phase corrected
Shot Auto-Align Post w/phase corrected


Using all three tools together as necessary, polarity matching, time alignment, and phase rotation, we can achieve the most well-defined, potent, and vivid reproduction of our recording. We built Auto-Align, Auto-Align Post, and Pi to eliminate guesswork and improve time/phase alignment across your workflow.

Auto Align 2


Auto-Align 2 is ideal for stationary multi-mic recordings like drum kits. It automatically corrects phase issues between mics and applies spectral phase optimization to fix phase shifts caused by the recording chain for a powerful, defined sound. With ARA2 integration, you enjoy zero latency and real-time track-based processing, so you can keep the plugin open while recording. The processing is applied instantly when you hit play, with no need to capture new clips. Streamline your workflow and achieve faster, more efficient results effortlessly.

Watch video demonstration


  • One-click workflow for fast and easy track alignment
  • Automatic reference and grouping detection takes the guesswork out of the alignment process
  • Spectral Phase Optimization for improved coherence and richer sound quality
  • Absolute Phase for faithful reproduction of sound directionality
  • Alternate optimized correlation editing for advanced users seeking creative control
  • Surround support for multi-channel applications
  • Single unified interconnected multi-channel user interface for efficient navigation
  • ARA2 compatibility for seamless integration with your DAW workflow
Auto Align Post


On a film set, you often juggle a mix of moving and stationary mics capturing the same scene—from lav mics and boom mics to multiple on-set mics, all capturing the story. By applying adaptive time alignment and spectral phase correction, Auto-Align Post 2 helps you bring out the true richness of your dialogue. With ARA2, you get real-time processing and a new track-focused edit window in Pro Tools, making your workflow more streamlined and intuitive than ever.

Watch video demonstration

  • Microphones time-alignment of up to ±100ms or distances of up to ~112 feet / ~34 meters
  • Spectral Phase Correction Module corrects phase-shift caused by electronic and acoustic filters
  • Dynamic mode enables continuous phase/time correction for moving actors or cameras
  • Static mode enables fixed phase/time correction for stationary microphones
  • Transparent Processing
  • Multi-channel support
  • Spectral Phase Correlation Meter
  • Highly optimized for CPU efficiency and operation speed
  • Easy to operate - no manual adjustments required

When tracks play together, they overlap and interact across the frequency range and phase position. Pi automatically adjusts the phase of each channel to minimize frequency cancellations and enhance the overall punch and depth of your mix. It’s essential for unleashing the full impact of your mix, ensuring overlapping frequencies interact constructively. It’s like having an invisible hand fine-tuning your mix to perfection.

Watch video demonstration

  • Groundbreaking, true multi-channel engine for optimizing phase interactions
  • Track grouping for related instruments and multi-mic setups
  • Full-range and Low-Frequency global optimization modes
  • Unique multi-channel display for viewing phase relationships within the mix
  • Internal sample-accurate routing, no side-chaining required

Feature Breakdown: Auto-Align 2, Auto-Align Post 2, and Pi

Sound radix chart

For recording and mixing music, we generally recommend Auto-Align 2, while Auto-Align Post 2 is ideal for post-production, and Pi belongs at the last insert slot of each of your DAW mixer channels.

Stay Aligned, Stay Creative!

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