Auto-Align allows you to correct time and phase alignment between two or more tracks recorded from the same source.
When you record two or more tracks on a single source, the sound waves arrive at each mic (or DI box) at slightly different times. This allows you to obtain a sonic character that''s impossible to get with a single mic. However, it can sometimes cause problems, especially with stereo sounds, because some frequencies will cancel out while others build-up unnaturally.
A graphical spectrum analysis (frequency vs. amplitude) of such a sound shows a distinct pattern of steep and regularly spaced peaks and troughs over the entire frequency range. It looks like the teeth of a comb and is called the “comb-filter effect.” This phenomenon causes inconsistent and location-dependent frequency response. It occurs in theaters, studios, or living rooms—any place where sound from the loudspeakers reaches your ears at different times.
Sound Radix''s Auto-Align ($149) is an AU/RTAS plug-in for Mac (a Windows version is coming) that gives you precise control over time alignment when combining two or more recorded tracks from the same source. When inserted on a track in your mix that you designate as the timing reference, it sends sample-accurate timing information over any one of its own eight internal buses to any other “satellite” tracks also running the plug-in, and then uses the DAW''s delay-compensation engine to make the correction. It also detects and corrects phase differences and polarity reversal between the source and satellite tracks. (Since this review was written, Sound Radix has added a switch to the GUI that makes it easier to compare the original and corrected sounds.)
I tested Auto-Align in Pro Tools 9 HD on a Mac Pro 8-core running in 64-bit mode. The plug-in installed quickly and was intuitive to set up and use. I tried it on a bass guitar recording comprising separate tracks for a DI and a miked Aguilar amp. I listened to the two tracks mixed equally without Auto-Align, and they sounded hollow and unusable (see 2a and 2b).
Auto-Align also has a polarity-reverse switch that lets you check how a track sounds flipped, but with the time correction applied. Another useful feature is the On/Off switch, which turns off all correction but leaves the phase correlation and spectral meters active. This is necessary because when bypassing on the plug''s GUI, you''ll hear its processing latency.
CORRECT THE PIANO
I also tested Auto-Align on a stereo Synthogy Ivory piano on which I''d compromised the stereo width to build more center-channel level (see Web Clip 3). With Auto-Align correcting phase only, I was able to maintain the original width while getting more punch due to a phase-accurate center image (see Web Clip 4).
The plug-in''s GUI has a delay display that shows the approximate distance between the two mic sources (tracks), expressed in your choice of samples, milliseconds, or inches/centimeters. The handy Prev and Next buttons allow you to “slide” the timing of the satellite tracks in real time, relative to the reference track—even negative values are allowed. The Way Back Machine lives! To use Auto-Align as an effect, I''d like to see delay time also expressed in musical subdivisions relative to session tempo.
LOCK UP THE ROOM
Auto-Align will time-align a distant room mic on a drum kit to match the close mics. On a multichannel recording, I used the close snare mic as my reference and sent it to a stereo Auto-Align instance on the overheads and a mono instance on the room track.
Correcting the overheads removed a slight delay that smeared the overall kit sound. The room track had a noticeable delay in the kick drum''s attack—a doubled attack that softened the overall kick drum sound. The room mic didn''t sound bad on the snare so I used the kick drum track for reference and sent its information on another bus to the room track''s Auto-Align plug. I ended up with a roomy kit sound with a sharper attack and focus on the kick.
Auto-Align is a wonderful tool for time- and phase-aligning multitrack recordings. It works accurately and automatically, and it takes the guesswork out of the time-consuming process of manually sliding tracks around the time line.
Overall rating (1 through 5): 4.5
Auto-Align Product Page