So during last weekend I finally got the time to test the new ATMOS output mode on XBOX ONE.
At first try it didn't work. The signal won't stay on ATMOS and kept switching to LPCM 7.1. Also HWK950 randomly showed "TV Speaker" on the front LED panel. I immediately suspect that the problem has something to do with HDMI CEC or ARC. So I went to the TV(Panasonic 65" Plasma VT60) menu and turned off any CEC related function and voila it worked. Not only did it output ATMOS signal successfully from Bluray disc or the Dolby Access app, it also transcoded everything including apps like Plex, Netflix and HBO Go into ATMOS and output it to the soundbar.
And the difference? Night and day.
I tested two movies that I have with ATMOS soundtrack. Batman vs Superman Dawn of Justice and Beauty and the Beast via Plex. In theory, since Plex transcodes ATMOS into AAC it should not matter what the output format is. But in reality, the difference is so huge that I can't believe it is the same soundtrack. LPCM 7.1 is the worst obviously since HWK950 does not support this format. But to my surprise not only did it lose all the surround info, the sound became really thin and bad to a point that I actually checked if it was my TV that was making the sound.
Outputting it as Dolby Digital is better. You can at least hear the bass again and the surround sound worked correctly. However, it still felt thin and boring and you just know that it is not delivering its full potential to you. Then everything changed when it was output as Dolby ATMOS. The rich and cinematic sound came back and it sounded so good that I cannot even tell the difference between the Plex transcoded sound and the pass through Bluray sound. All the upfiring unit worked although it may not be using the correct height sound info but it still sounded really good. Ben Affleck's voice sounded so much richer as if you are watching the film in cinema.
The only problem I have with this mode is that unlike the DTS and Dolby Digital output, the system does not keep the audio signal alive when there is no sound. So the soundbar will enter a standby mode if there is no constant sound. It takes the soundbar 4-5 seconds to pick the signal everytime it comes back. The feedback chime sound will almost never work because of this. Hopefully Microsoft will fix this and send a dummy audio signal constantly even if there is no sound.