I'm having a very weird problem. Actually, a couple of problems.
OPPO 203 UHD player - set to Bitstream, Secondary Audio turned off
I'm on the latest firmware for the X8500H, but I noticed this problem before I installed it. The firmware update did not fix it.
I alternate between two configurations:
9.1.4 (Front Wide, Surround Back, Front Height & Rear Height) for Dolby Atmos soundtracks.
9.1.2 (FW, SB, FH) with Neural:X upmixing for everything else (due to the DTS 11-channel limit).
I have also tested other configurations without the Front Wides. Disabling those didn't make a difference.
Playing: Spears & Munsil HD Benchmark calibration Blu-ray.
This disc has 7.1 test tones in your choice of Dolby TrueHD or DTS-HD Master Audio formats.
Playing Dolby TrueHD 7.1 test tones with my default setting of the Neural:X upmixer, the Surround Back tones play from the left and right Surround speakers. The Surround Back speakers never turn on.
The receiver's own internal test tones work correctly from all speakers. The Info menu shows that the SB speakers should be active, but no sound comes from them. It repeats in the Surround speakers instead.
This only happens using Neural:X. Using the regular TrueHD setting or TrueHD with Dolby Surround Upmixer, the tones play from the SB speakers.
I next put in a regular movie discs with both Dolby TrueHD 5.1 (The Dark Knight) and TrueHD 7.1 (Legend of the Fist) soundtracks. Neural:X seemed to work correctly on both. I heard audio from both the FW and SB speakers. But it will not work with the TrueHD 7.1 test tones on the Spears & Munsil disc.
Also 9.1.2 configuration.
The DTS-HD Master Audio 7.1 test tones will play from all 7 ground speakers, but the Neural:X upmixer has vanished from my list of Surround Mode options. I can choose raw DTS-HD MA, DTS-HD with Dolby Surround, or Auro-3D, but Neural:X is completely gone!
Neural:X is available when playing the TrueHD 7.1 test tones, but not the DTS-MA test tones.
Again, I followed this up by playing a regular movie disc. Deadpool has a DTS-HD MA 7.1 soundtrack. Neural:X is available this time.
Further, when using it, I do get audio from both FW and SB speakers.
I also tried a disc with a DTS:X soundtrack (A Beautiful Planet). I could hear audio from the Surround Backs, but not the Front Wides. After a moment of puzzling over this, I remembered that most DTS:X tracks are authored as 7.1.4 channels with no sound objects, so the FW speakers will never get used with those. I guess I'll switch to the Atmos configuration with 4 heights when playing those.
I suppose the most obvious conclusion should be that there's something wrong with the authoring of the Spears & Munsil disc. I could swear that I've played this disc in the past and never had these problems before, but I'm not sure I was using Neural:X at the time. Since the SB speakers work fine with DSU engaged, the issue may not have ever come up until now.
Even if it is a disc authoring problem, though, how does that explain why the Neural:X option vanishes from the X8500's Surround Mode menu?
Can anyone else who has a copy of this disc test with Neural:X to confirm if you see the same thing? Thanks.