Tips for Audio Engineering Students: Quick Phase Check in Pro Tools

Use this trick in your DAW (Pro Tools, Logic, Cubase, Ableton Live, FL Studio, Digital Performer, etc.) to make sure your tracks are phase coherent!

For audio engineering professionals, checking for phase coherence in the tracks is as important to the music they mix as checking the focus is to a photographer.  Phase relationships are a subtle part of the overall mix, but they’re important, and recording tracks that have phase issues will result in music that sounds ‘blurry’ or unfocused.  When given a song to mix, one of the first things I do is check to make sure all the tracks are in the best possible phase relationship with each other.  When working on an analog console this process is easy.  On all professional mixing consoles there is a phase reverse button, which is usually located near preamp section of the channel.  While listening to the tracks (usually in mono), I simply run down the board flipping the phase on any channel I might suspect to be out of alignment with another (i.e. the kick track Vs the overheads or a bass amp Vs a bass DI track).  After a few minutes of assessment I am able to diagnose and correct any major phase issues, which may have led me to make unnecessary level and EQ adjustments down the road in the mix.  This simple task has been made not so simple in the DAW world as there is no longer a phase reverse button on every track.  Now, in order to reverse the phase of a track in the digital world you must either insert a plug-in on the track, or render the clip with some sort of file based phase inversion process (Audio Suite processing for Pro Tools users).  Both of these methods are not nearly as simple and convenient as flipping a switch.  To accommodate this minor inconvenience, below is a technique that I use in Pro Tools to simulate a phase reverse switch on every track.

Step 1: Insert your plug-in EQ of choice on every track on your session.

Regardless of your EQ choice, the same plug-in should be inserted on each track and the EQ should be kept flat.

(You could use any plug-in which offers phase reversal.  I find EQ plug-ins work well for this as almost every one has a phase reverse button along with the added benefit of acting as your channel EQ)

Step 2: Flip the phase on every track.

(For quicker workflow in Pro Tools, insert the EQ on the first track in your session, flip its phase and then hold Option(mac) or Alt(win) and drag a copy of that plug-in onto all other tracks in your session)

Step 3: Bypass the EQ plug-in on selected tracks.

Play the song back and bypass the EQ plug-in on any track you want to hear in the opposite phase relationship to the other tracks. (This can quickly be done by holding command(mac) or Ctrl(win) while clicking on the plug-in in its respective insert slot)

After a quick pass through all the tracks in your session, you should be able to audibly diagnose which tracks are in phase or out of phase with each other.  Listen for an apparent increase or decrease in frequency content while flipping a tracks phase.  Some common problem tracks are inside and outside kick mics, snare top and bottom mics, as well as the overhead mics VS the kick and/or snare mics.  I often will sum the mix to mono while checking phase, as any cancellation will be much more apparent while listening in mono versus stereo.  Experiment with different configurations of bypassed and un-bypassed plug-ins until you achieve a sound that is right to you.  The benefit of this setup is that you can quickly audition different phase configurations until you have achieved a sound that is right for you.