If you’re like me and use iTunes for some basic audio playback at events, you may have stumbled across various phase related issues with certain tracks. For me, I found it particularly horrid when using “Split Tracks”, where the vocals are on one track and the backings on the other (these types of tracks can be handy in churches where you have no live band).
Phase issues generally manifest themselves by making your audio sound thin, washed out or eliminating everything in the “centre” of the stereo image (typically the lead vocals). I also found a problem where splitting the left and right outputs into two separate channels on an audio console resulted in a strange situation where increasing the levels in one channel decreased the volume in the other, and vice versa.
The solution is to turn off the “Sound Enhancer”. This can be found in the Playback tab of the iTunes Preferences window (under the “Edit” menu on Windows, or the “iTunes” menu on Mac).
As for what the “Sound Enhancer” does, Apple claims it is a simple Bass and Treble boost. User “blueintheface” from LogicProHelp.com thinks it goes a lot further:
“What iTunes does in this respect is the same as the ‘Wide’ button found on ghetto blasters in days of yore – some high frequencies from each channel are phase-inverted and fed to the opposite channel. This makes the stereo-width apparently greater – but comes at the expense of any real definition of placement. It might be instantly appealing in its queasy-making phasey-ness, but in reality the whole stereo image is smeared. It’s an effect that destroys any spatial naturalism to any recording, and so wouldn’t be suitable for use on any ‘realistic’ recordings say of an orchestra or a jazz band. I’m not saying it doesn’t have its place – because someone will probably have a hit with the most artifically widend (sic) track next week – just to be aware of what you’re doing, and sometimes what is instantly appealing ends up ultimately fatiguing.”