If you've ever recorded a drum kit or multi-miked other live instruments, you've probably spent time moving the mics around to prevent frequency cancellation. Later, you may also have nudged tracks back and forth in time in your DAW to get the punchiest, tightest sound.
Auto-Align from Sound Radix addresses this second scenario, providing you with a 'point and shoot' solution that claims to automatically suss out and apply the optimum delay time.
Auto-Align uses a straightforward concept: insert the plug-in on the channel you want to pull into line and use the sidechain input to feed it a reference track to match it to. It analyses both signals and applies a best-fit delay (positive or negative) to the target channel.
It's strictly a time delay process - there's no phase rotation à la Little Labs IBP, and no stretching of audio. The metering is colour-coded to indicate frequency content, and input and sidechain meters also indicate frequency content by width (wider is lower).
The applied delay is indicated in the top right, with the delay length indicated in samples, milliseconds, centimetres and inches. Detection is activated using the 'detect' button, and you have two options - 'delay' or 'delay and polarity'. The latter will also correct for signals that are out of phase - ie, opposing polarities.
Line 'em up
Both input and sidechain meters have a noise floor control. This affects the analysis (the resulting audio isn't tampered with) and is designed for filtering out bleed, which is useful for drums.
The main phase meter is a goniometer, but coloured according to frequency. Once AA has done its thing, it should tend towards a vertical line. Finally, in 'delays' mode, the meter shows a waveform indicating good match points. It defaults to the strongest match, but you can skip to other points for different tones.
In use, this is all very simple and Auto-Align copes well with typical situations, such as the good old problem of aligning the top and bottom snare mics. Room mics raise a couple of issues, and with multi-miked kits, you'll have to choose which track you want to be the 'master' to which the others sync.
With complex mic setups, carelessly applying delays to tracks could cause more problems than it solves, so Auto-Align needs to be used sensibly.
Get a room
Shifting room mic tracks in relation to those of the close mics is a time-honoured production trick. Auto-Align makes this process simpler because it finds a number of good fit points, so you can plump for one that's still offset from the close mics, but more in phase with them.
There are a couple of practicalities worth mentioning. First up, if you're planning to accurately match the close mics to a stereo room track, you need to be sure you're feeding both sides of the stereo room to your sidechain.
In Logic, you'll have to mono (sum) your room signal temporarily while Auto-Align analyses the signal. Next up, Auto-Align only compares two tracks at a time, so you need to decide what order to do them in.
Aligning everything to the overheads seemed to work best for us, but bussing our kick and snare together as a sidechain for aligning our overheads and room also worked well.
The maximum delay is ±881 samples (around 20ms at 44.1kHz), which covers the majority of situations, but doesn't allow for extreme ones. Beyond drum kits, we found Auto-Align worked best when there was a decent distance between mics - ie, close and room mics.
When the mics were already close, improvements were harder to come by or just resulted in subtle tonal changes, as a mic adjustment would.
It's true, of course, that you can align audio tracks by hand and achieve essentially the same results, but doing so does require time and skill. Auto-Align, while not being essential, is a great time and sanity-saver that will appeal to anyone working with multi-miked material.
Now listen to our audio demos to hear:
Drums: First we're matching our room mic to kick and snare by using a grouped kick and snare as the side chain. So, we've got the original blend kick, snare and room mics. Next we hear the result after Auto-Align has worked, adding a 428 sample pre-delay to the room mic. Next we adjust the delay manually to another point with a +209 sample delay, adding distance. Next we use the same process but for our overheads. This time AA gives us a 153 pre-delay.
Snare drum: First the snare top then the top with the bottom - note how adding the bottom is causing phase cancellation. Now by applying Auto-Align to the bottom mic, it applies a 30 sample pre-delay and phase reverses it, resulting in a punchier sound.
Drums 2: Now we're trying to align our kick and snare to the overheads. So, first we hear the original mix then with snare aligned (140 sample pre-delay) then with the kick aligned (163 sample pre-delay) then back to the original mix to compare.
Electric guitar: Here we have a guitar amp recorded from both the front and back, and we hear the front mic, the rear mic and then the combination. Now we apply Auto-Align to the rear mic and it reverses the polarity and applies a 10 sample pre-delay. The result is a nice full sound. Finally we skip through various of AA's other best fit points for comparison.