Hello guys,
This is my first post here and I start with grave digging, but with a reason - few posts from head-fi are top results in google when it comes to one IE8 channel (right / left - doesn't matter) being quieter and - after trying different things for more than a year - I think I finally found a solution.
Note that this solution will probably not help if you've totally lost sound in one / both channels.
The issue is with the connector - not the cable pins, but the sockets in the earpieces themselves. You need a very thin needle that can easily fit in these sockets and a bit of an alcohol. I strongly suggest IPA.
Just spray a bit of the alcohol on the needle, remove the excessive amount (should be just a tiny drop on the tip), then insert it into the socket and rub it back and forth against the socket walls few times. Repeat several times going around and pushing against different spots of the socket walls (yes, this is still about restoring the sound in IE8...). The needle insertion should be quite easy and for at least ~2 mm deep - if it's not, you need a thinner needle. Repeat for the other socket (and proactively for the other earpiece) and voilla - no more sound level difference.
I've tested this solution for half a year before posting, just to make sure it works, as previously tried solutions provided no fix or (accidentally, it seems) up to two weeks of solving the issue - then it returned. Posting it in these few top posts suggested by google - hopefully I won't get banned as a spammer, really doing this in a good faith.
Cheers!
KoRni