Agree, there seem to be different issues: I have the issue of low, tinny sound, not crackling/popping. My issue did not exist when I first used my S2, that I bought a month ago, in fact I was even impressed by the spatial sound when playing a Netflix movie. Since I used mostly my headphones, I did not discover the issue until recently. The low tinny sound issue is not related to applications: movies, music all the same issue. I cannot decide on hardware or software. Many software updates are done in the background, but there must also be some "switch" sensing the difference between sound setting for headphone or speakers. (Strange: while I am typing this on my touch cover I seem to hear only sound from the right speaker, and sometimes it is lacking. I remember reading that in this thread as well.)
I will continue to follow this thread: if it is software, it will get solved, if it is hardware, no use exchanging until the hardware is improved.
I am too happy with my S2 until now and I do not want to return it,..... yet.