No actor's voices: changed Realtek config from "stereo" to "5.1"

[goodenough]

I have the Logitech X-540 5.1 Surround Sound speakers. I just upgraded to a new PC. I went into the Realtek HD audio manager, and changed the speaker config from "stereo" to "5.1 speaker". When I played a DVD movie, the actor's voices were muted out, but all other sound was audible. I put if back to "stereo", so I could watch the movie. Anyone know what I should do?

I have 3 colored jacks coming out of the soundcard.
The subwoofer has 8 cables going into it:
The 3 mini Green, Black, Peach trio,
and then the 5 bigger white, black, peach, red, yellow jacks.
All 5+1 speakers emit sound when in stereo mode.

http://www.amazon.com/gp/product/B000JJM8XE?m=ATVPDKIKX0DER&tag=at055-20

 

[goodenough]

I just did the speaker test. Turns out, I had to uncheck all the "optional speakers" to get the center channel working.

However, there is still a problem.

In "5.1" mode, the rear pair of speakers don't work. When the rear speakers are tested, the sound actually comes out through the side pair of speakers. Also, no sound comes out of the subwoofer during its test.

Under "quadrophonic" mode, 4 speakers work independently (2 sides, 2 rears), however, the middle speaker (the one that plays the voices in 5.1 mode) isn't part of the config (presumably b/c only 4 speakers are part of this config)

Any ideas?

Edit: Damn, I just went back and CHECKED all the optional boxes under 5.1, and now all 5 speakers work independently !?!

Actually, I had to turn the Matrix button OFF to get the surround sound working. Go figure!