Hmm... that's strange. I tested youtube myself and noticed some weird things.
Using default Flash Player web-player, the sound comes out of all channels. FL FR C RL RR Sub.
Using HTML 5 web-player, the sound comes out only in stereo. FL FR +Sub (And that's actually correct)
In other cases, where I have forced 5.1, I can't turn it off back to stereo! LOL!
I never use any enhancers from Phoebus control panel or anywhere else, because those are bullsh**. Surround Max works for me, but it cuts bass, and I don't know why. LOL again.
When playing games, watching a movie or listening to music in special programs, everything is perfect. (For example Foobar2000 - stereo is stereo, multichannel is multichannel. With integrated Channel Mixer I can upmix stereo to 5.1)
Try to activate Dolby Home Theatre if you are using Win 7. Otherwise "throw that piece of sh** out of your window." :cool: