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Phase Out Phase: Quick and Easy Automatic Double Tracking in Logic
Mike Watkinson on Sat, June 11th | 3 comments
Whether invented by accident by Les Paul or, as others say, by Ken Townsend at Abbey Road in 1966 (and used on John Lennon's voice), automatic double tracking (ADT) is a way of thickening...

Whether invented by accident by Les Paul or, as others say, by Ken Townsend at Abbey Road in 1966 (and used on John Lennon's voice), automatic double tracking (ADT) is a way of thickening and creating a stereo image from a mono recording, as if the performer had indeed recorded a near identical part for a second time. It continues to be a key feature of record production especially for vocals but often for guitars and other instruments, and is typically used to differentiate between verse and chorus. This quick tip shows you a quick way to create the effect in Logic Pro, and then a way of checking for the problem that it may cause!


Step 1 

Duplicate the track on which the audio region is playing back (the default key command is Command-D


Step 2 

Make a copy of the audio region by Option-dragging it to the duplicated track.


Step 3 

Pan the two channels hard left and right. You might think that this is all you need to do, but if you think about it, all you have done is recreate what happens to a mono source when panned centrally, the only difference being that it will be 6dB louder!


Step 4 

Insert a Sample Delay plug-in on the copy track. The idea is to recreate the effect of the second part hitting your ears at a different time from the first, so the higher the number of samples delayed the further apart the two versions appear to sound. Up to a certain point the effect is as though you are listening to a single sound that seems to have ‘width’, but beyond that point, it sounds more like two separate sources.

A typical set up in Logic Pro for quick and easy ADT

A typical set up in Logic Pro for quick and easy ADT


Check for Phase Problems 

The problem with this method is that phase cancellation might occur when the mix, which you have monitored in stereo, is played back through a mono system such as  a cheap TV or kitchen radio. Plenty of great records suffer from phase cancellation-related issues when auditioned in mono: later Beatles albums have been criticised for their poor audio quality when heard in mono, and the guitars on Nirvana’s Smells Like Teen Spirit definitely suffer compared to the same track heard on a stereo system. 

You can test your mix by bouncing in mono. Go to the Output channel strip (normally stereo), click the mono/stereo format button to change it to mono, then click the Bounce button on the channel. 

Note: this option is not available when bouncing from the File menu or the toolbar.

The Output Channel strip configured in mono

The Output Channel strip configured in mono


You can also check for potential phase-related issues by using Logic’s Multimeter plug-in, and selecting the Goniometer display. This usually displays some dancing string, so it is useful to know what you are looking for! Anywhere between tall and thin and perfectly circular will be fine when auditioned in mono, but if the circle start to flatten, this is an indication of potential problems, with the worst case being wide and flat!

If the Goniometer display shows something between the first and second images, you should be OK when listening in mono, but not if it starts to look like the third image!

If the Goniometer display shows something between the first and second images, you should be OK when listening in mono, but not if it starts to look like the third image!


Check back for a follow-up article that will show you how to recreate ADT without phase cancellation problems!


Comments (3)

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  • Dekuruy
    Thanks Mike. Although I've used this technique, I never knew how to check for phase issues. Very helpful!
    • 7 years ago
    • By: Dekuruy
    Reply
  • ISAAC FABREGAS
    Thanks a lot Mike. Always we use a delay with an exact copy of the track to get this effect we'll have phase problems if we listening in mono. This happens because there are same frequencies on the right and left channels, but with opositive phase. When we listening in mono, we sum this two channels; so there are opositive phase in identic frecuency contex we get a destructive sum between these frequencies; no sound occurs, "cancellation". Its true we can check this problem, but the main history also is that we only can check it, no resolve it. Definitely if you like, (need), this effect you'll have sure phase problems in mono. There is a technique that sends different frecuency context to left and right channel, simulating stereo feeling without delays. This technique doesn't have phase problems, so the frecuency context that in this case is sumed on mono listening, is different. If this frecuency context is different we don't get opositive phase in identic frecuencies (our problem when we sum on mono). Instead we get a constructive sum (sometimes, not absolutely constructive occurs, but never we get cancellation). Sound occurs, no cancellation. I wish to read your next article Mike.Very interesting. Thanks again!
    • 7 years ago
    • By: ISAAC FABREGAS
    Reply
  • Rounik Admin
    Yes! Nice article Mike! @Isaac, if you wish to view all articles already published by a particular author click on their name under the title at the top of the article: http://www.macprovideo.com/hub/author/mike-watkinson Keep checking back for new articles as we're adding at least one daily! Cheers Rounik
    • 7 years ago
    • By: Rounik Admin
    Reply
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