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iTunes Soundcheck causing distortion
Old 6th December 2017
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iTunes Soundcheck causing distortion

I have mastered several tracks recently with an integrated loudness value btw -13 and -15 LUFS. I've been careful to ensure the dBTP value is at least -1.5 to -2.0 to try to ensure there are no intersample peaks.

I would expect Apple's sound check to turn these masters down. Instead it turns them up considerably, to the point of causing audible distortion when listening via car speakers via Apple Music (via bluetooth or via USB connection, streaming and without streaming). I have read that dynamic range or PLR has a lot to do with how soundcheck works. Perhaps my masters have too much dynamic range?

Just seems that other masters I have heard with similar or higher integrated LUFS values get turned down when sound check is enabled.

I appreciate your comments and thank you in advance!
Old 6th December 2017
Is the equaliser on iTunes enabled, or the "sound enhancer"? These can cause clipping very easily.
Old 6th December 2017
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The scenario where I hear it is in the car via the iPhone Music App. Soundcheck is enabled, EQ is off since I am using the car’s treble, bass. There is no sound enhancer option via this app. I leave these settings the same and turn sound check on/off to compare my tracks to the other tracks mentioned.
Old 7th December 2017
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Could it be that there is a difference in the way sound check works for music in “Your Library” versus music in “Apple Music”?
Old 12th December 2017
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Old 12th December 2017
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Greg Reierson's Avatar

Verified Member
Something is busted. Maybe the latest iTunes / OS release has a bug? That's not how it is supposed to work. Maybe try it on a different computer / OS.
Old 16th December 2017
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It works as expected in iTunes (turns the tracks down slightly) but turns them way up in the music app on the iPhone.
Old 11th May 2018
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rsjc's Avatar

Yep, SoundCheck on 11.3.x still "busted"

Following massive distortion when connecting an iPhone 7s via Bluetooth receivers (Apple's and others), I turned off SoundCheck and noticed as the original poster did, that tracks were being boosted where one would expect them to normalize down.

Rather sad and ironic that I must turn off one of the cures for the loudness war to listen to loudness war victimized tracks. Lots of indication online of ongoing issues. I've experienced problem with mp3's and AAC files.

It would be rather absurd if some programmer thought it a good idea to maximize if and when there is not a gain setting associated with a file.

At any rate, glad I'm not alone in debugging Apple's money makers for them.
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