I think the Sonos Playbar is a fantastic piece of equipment on it's own and perhaps with a sub for 3.1. However, with respect to the ability to add a pair of surround sound for 5.1s... I'm at a huge loss. Considering:
a) 99% of TVs will not output 5.1 sound from HDMI inputs over optical
b) TV manufacturers do not advertise this spec on their TVs so it's difficult or impossible to determine in advance
c) Sonos refuses to maintain an official list of such compatible TVs on their website
I don't understand why Sonos would advertise the Playbar as being 5.1.
Yes, you could get the Playbar to output in 5.1 if you add an A/V receiver and possibly if you use an HDMI switcher, although the switcher is iffy because of how HDCP handshaking works, it still might only output 2.1. Also, there's reports of HDMI handshaking failing between switches, which requires turning the TV and connected device on and off each time you use it.
But here's the problem-- the Playbar, or any soundbar, is supposed to be used when a person wants a simplified home theater setup, with minimal wires, minimal components, and minimal fuss. If you add an A/V receiver or switcher then it's no longer minimal.
So what exactly was Sonos thinking with the Playbar? Don't get me wrong, I enjoy mine for the 2 channel sound it is. However, it's going to be virtually impossible to reliably and easily get 5.1 out of it. And then even if you can, it won't do DTS but that's been hammered to death ad nauseum already.
I actually bought my Playbar with the thought that I could buy a new TV that outputs 5.1 over optical from HDMI inputs, because in a few months I'll be in the market for a new TV. Unfortunately, it still appears that I will be unable to reliably make a purchasing decision due to a dearth of information on what TVs will do this.
My initial question - What was Sonos thinking? remains. Clearly there was some discussion on this in the engineering room during R&D. Here's the best I can come up with:
1) The Playbar can take a 2.1 signal and put out a crappy faux 5.1 version that is extrapolated, and won't sound anything like real 5.1, but the average Sonos consumer is too ignorant to notice that the sound out of their rear $300 each speakers is really just a slightly quieter version of their front channel.
2) They didn't perform due diligence and didn't realize so few TVs output 5.1 over optical, and just assumed it would work.
Those are the best two explanations I can come up with, and neither of them make Sonos look good. I'm open to other possibilities, but when I contacted Tech Support asking them about a list of TVs that support 5.1 over optical, Sonos official CSR basically told me to screw off and I'm on my own. MAYBE Sonos created the Playbar with the idea that 99% of their customer base would NOT use it as 5.1, and Sonos was "nice" enough to add the functionality to pair the Play:3s for 5.1, for the 1% of hard-core customers that might want it, and Sonos figured those people would be able to parse through the methods of doing that on their own. That would be a reasonable thought, perhaps.
What was Sonos thinking with the Playbar regarding 5.1?