Recording - October 2016 - 52

5. Dealing with phase issues
Now's the time to make sure related tracks are
all in phase. Phase is easily worthy of an article (a
book?) all by itself, but in the context of this article,
it's important to remember that the phrase "out of
phase" is used to describe at least two very different conditions. One is electronic phase (actually
polarity); the other is phase differential caused by
differences in time alignment.
Polarity changes can happen for a variety of
reasons: the channel on the mixer or interface has
its "phase" button pressed, a piece of gear is
improperly designed, a cable is miswired, or
there's a piece of gear in the recording chain that
follows the opposite wiring convention for its balanced input or output. Most audio gear built these
days follows the standard of "Pin 2 Hot" (Pin 1 is
the ground, Pin 2 carries the audio signal ("hot"),
Pin 3 carries an inverted copy of the signal
("cold") to cancel out radio interference). However,
a lot of vintage gear follows the opposite rule and
has Pin 1 Ground, Pin 2 Cold, and Pin 3 Hot.
(How will you know? Read The Freaking Manual!)
When any of these things happens, the signal
arrives at your DAW inverted from its actual polarity... and if it's part of a group of tracks recorded at
the same time, it will trash your audio. You can
easily hear this for yourself by taking any mono
track in your DAW, duplicating it, and flipping the
polarity of the copy, panning them both to the center, then comparing them by turning the level of the
copy up and down. With the two tracks at equal
level, they cancel each other out completely and
you have silence; at unequal levels, you'll hear a
hollow, phasey sound that lacks power and depth.

Part 2:

Phase issues, signal processing, levels, and voices
By Bruce Kaphan

In Part 1 (September 2016), I laid out a general approach to
getting ready to mix recorded tracks, whether you were also the
recording engineer or you're being given tracks recorded elsewhere. This involves eight steps:
1. preparing the work area for maximum efficiency
2. creating a panning scheme
3. cleaning clips: muting, fades, and crossfading
4. dealing with noise
5. adjusting for phase issues within groups of simultaneously
recorded (or combining re-amped with source) tracks
6. modifying the essential nature of a track through signal processing
7. leveling a track or group of tracks
8. building a palette of FX voices (reverbs, delays, etc.)
Last time we got through the first four steps; now it's time for
the rest!
52

RECORDING OCTOBER 2016

Spotting polarity-inverted tracks can be as simple
as a visual inspection of the waveform. Tracks
recorded at the same time should all have their
waves moving up at the same time, then down at
the same time; a track that's inverted will look the
opposite. Try inverting its polarity and see if that
makes the sound stronger and more robust.
Time alignment is a little more complicated. Sound travels fast (1126 feet per second), but it's not instantaneous,
so two mics picking up the same sound at different distances will be out of phase to some degree or another;
when the sound wave hitting one mic is at a peak or
trough, the same wave hitting a different mic an instant
later may be near zero. This is a particular problem when
close-miking a drum kit. When you're doing minimalist
miking (two overhead mics and nothing else, or a 3-mic
Glyn Johns setup), you can usually minimize phase issues,
but what about close miking?
In mixing, after visually inspecting the tracks to
make sure the waveforms all appear to be in
phase (as described above), methodically make
sure tracks in a group of simultaneously recorded
tracks are in phase by doing the following test.
Start with all tracks panned to exactly the same
position (choosing center is a good idea for this
test), with all tracks as close to the same output
level as possible, with delay compensation
engaged and all plug-ins turned off. Choose one
channel, listen to it, and pay attention to the peak

Table of Contents for the Digital Edition of Recording - October 2016