I'm using Plex 0.8.2 on Mac OS X 10.5.7 and have it hooked up to a Sony HT-CT100 Sound Bar using a Toslink to Mini M/M OD:5.0mm, Molded Type - 6ft [monoprice/products/product.asp?c_id=102&cp_id=10229&cs_id=1022902&p_id=1557&seq=1&format=2] cable bought off Monoprice.
I have a lot of 1080p high definition MKVs with 5.1 channel audio in my collection. Whenever I play any of those movies, the volume of the vocals is so low they're almost imperceptible. The rest of the sounds (music, background score, sound effects, etc.) are generally quite loud (sometimes deafeningly so). I've tried changing the settings on the speaker system itself and nothing has worked.
It's worth noting that movies with 2.1 channel audio always play loudly enough, and so does music. I know that it's not a problem with my 1080p MKVs because when I play the same movies on my system through a cheap set of 2.1 speakers (owned by my friend), they're always loud and clear.
I'd initially thought it was a problem with Plex but I've come to realise that that isn't the case. The problem occurs only when I connect my sound bar and persists across iTunes and QuickTime Player as well. I've tried Googling for a solution but haven't been able to find any solution on my own.
So this is an earnest plea for help. I have very little knowledge about anything to do with sound and spent a lot of money on buying this sound bar and getting it legally imported into India. I'm pretty sure I'm doing something wrong because there is just no way such an expensive and well regarded piece of equipment can have such a major flaw. Please advise me on how to go about trying to fix this.