You will only get stereo with DTS content. Some blu rays can reencode DTS to Dolby in real time.
As for "real 5.1" sound. I found that every time i turn off the set (or it goes off by itself) and start it up again the channels with bug out (sound from rears will bleed to front L/R accordingly) and it will stay like that until i disband and remake the surround group again.
This is a problem with Multiroom itself, not TV related as it also happens with 5.1 audio file i play through WiFi from my tablet. Right after making the surround group everything is fine, all channels are separated. After turning the set off and on again, channels will mess up.
I just tested it and if you play a DTS5.1 movie (after setting the output to DTS in your tv's audio settings) the rears and the center channel will stay silent, so it obviously downmixes to DTS 2.0
@Simon_w: I'm on a HW-J650 which is I guess very similar to the HW-K650. But it's a 4.1 instead of 3.1, which means it has 2 center speakers. Then 2x R3, a UE55JU7090 and a PS4 as a bluray player. The R1s have the new firmware 3112.5. The sound bar is 3109.2 and is the newest for my model. Yesterday, I did test with the optical connection and it worked wonders. True 5.1 on Dolby Digital blurays with TV audio set to Bitstream and Dolby Digital. Great sound and the R1s volume was matched perfectly to the soundbar. Balance for all speakers set to 0 in the group. Then tested DTS only bluray with TV audio set to Bitstream and DTS. I can confirm Peejay84's observation. It is a pathetic stereo sound with my center speakers and R3s silent.
@Peejay84: Thanks for the tip with the bluray players, which can transcode DTS to Dolby Digital on the fly. This will be the next thing I will buy.
Then my observation with optical connection and regular TV (HD and Dolby Digital audio (sometimes), I've again noticed the sound and lips are not synchronized. I don't remember which comes first and have not played with settings. But I think the default was set to 80 or 90. If the source was real Dolby Digital 5.1 again, I get very good surround sound with the R1/soundbar volumes perfectly matched. But when it the source is only stereo, the front speakers are mirrored to the rear ones. This will lead to very echoy voices at higher frequencies (women speakers). Lower frequencies don't produce this echo effect. I guess it is because they are supported/provided by the sub woofer? Anyway, I have to ungroup the sound bar/speakers with regular TV shows otherwise the echo makes me go crazy.
My next tests will be 5.1 test material from USB-stick and check the sound-lip-sync.
I can infirm it works like that with my R3s, although they still aren't as loud as with optical connection and changing the volume will revert them back to being silent.
Theres a little part of me that feels very sorry for this engineer - I bet he has no idea what he is walking into...
But the big part of me feels he deserves everything he gets !!!!
Good luck Rob - lets hope this is the final hurdle before the fix...