My brother's Note 2 definitely was crackling on speaker when listening to some ripped Youtube mp4's he downloaded. If he lowered the volume a good some then the crackling went away, but on max volume it was definitely noticeable. I also believe it has something to do with the quality of the file itself. One music video he had was rather low quality and the crackling was much more pronounced than the rest. Where-as on a high quality video the sound was almost crystal clear.
Hard to say yet but it seems they're allowing us to push the dB's up a little too high on the speaker causing distortion.