MarkGB

Page 26 of the manual has the process for this. You can download it as a PDF from the Bar 48 page, on the Klipsch site. I got my Bar 48 at launch and don't recall this being in the manual so it might have been added to more recently.

Since the firmware update, I can use HDMI now (CEC, ARC) on my Vizio P75 and don't have any audio problems at all. Before it would lock up when you powered off the TV so I had to fall back on optical only but HDMI seems to cure the problems. I also get the sound coming on quicker with HDMI than I did with optical and occasionally I would switch inputs and have no sound until I switched inputs and came back one more time - again, this does not happen with HDMI. So not really a fix for the optical but if you have the choice, might be worth exploring the HDMI only route. I disconnected my optical or it seems to over ride which cable gets to run the audio.

I noticed similar with mine a couple of months back but it was when I watched TV. I had to force the TV to output Dolby Digital (which is what the satellite box was outputting). The TV on Auto, Bitstream or DTS could (not always but enough to be annoying) just output the soundtrack otherwise and you would get no voices. First time I noticed was a basketball game - great audio of squeaky sneakers and crowd but no commentary. When I fixed the output to just Dolby Digital, I don't have this problem. You haven't said what your source is for Netflix but I would check and adjust the sound settings there and on the TV and see if that helps.