Bass management and the APM89 bass and treble are 2 different things. Are you aware of that? Maybe I'm just confused because you mention them more or less in one sentence.
IMO with the BBC and Surrey rooms you don't need bass management, as I think every speaker there has been bass managed already in the room and was recorded full range in the PRIR. That at least I presumed based on my 2.0 stereo music listening with the Surrey room.
I have read the user manual and understand how bass management works there, but it doesn't seem to make sense with my Realiser using 24ch rooms.
I'm using my own rooms naturally here, those preset rooms are just not up to the bar with my own measurements. Bass is just a problem as I used my old satellite speakers which are rated 120-20Khz and naturally you don't have bass at all with those on measurements. I know, this is stupid, but currently, I'm with these.
At least SPDIF should be possible to upmix to at least 16ch by the upmixer I think. Does this work in 16ch mode? And in 24ch mode it doesn't upmix? Try not only switch the upmixer on on the PCM audio management page of the preset but also the normal Dolby Surround upmixer on the preset. I think Imencounterd last time that PCM upmixing only worked when both settings are on.
You can only choose HDMI1-4 as inputs when you activate 24ch, there's no way to choose others at least I don't know-how.
So far I only saw the side center speakers mixed up. They are named Lsc and Rsc in the Realiser (Left side centre,...) and they named them Lcs and Rcs in some documents.
What other channels you found with different names?
Mandatory are the names inside the Realiser, in the Ref column for example when you load a specific listening mode to a listening room. And then the PRIR you choose must have speakers with the same labels as Vspkr.
If you look March update and 15.1.8 description: 5.1.8ch (C, Lcs, Rcs, L, R, Lw, Rw, Ls1, Rs1, Lss, Rss, Lrs1, Rrs1, Lb, Rb, Lfh, Rfh, Ltf, Rtf, Ltr, Rtr, Lrh, Rrh, SUB)
for example Lhr = Lrh
Also when looking user manual and this table on manual page 98, there's also mixups with those 3 letter acronyms. Also if you compare manual page 98 to internal names of the Realiser you'll notice differences. There's internal channels compared to page 98:
1. L
2. R
3. C
4. SW
5. Ls
6. Rs
7. Lb
8. Rb
9. Lss
10. Rss
11. Cr
12. SW2
13. Lw
14. Rw
15. Lbs
16. Rbs
17. Lc
18. Rc
19. Lg
20. Rg
21. Cg
22. Ch
23. Chr
24. T
25. Lh
26. Rh
27. Lhs
28. Rhs
29. Lhr
30. Rhr
31. Ltf
32. Rtf
33. Ltm
34. Rtm (Ltm)
35. Ltr
36. Rtr (Ltr)
37. Lsc
38. Rsc
39. Ls1
40. Rs1
41. Lrs1
42. Rrs1
43. Lrs2 (marked 44 on map)
44. Rrs2
45. Lhw
46. Rhw
47. Lhs1
48. Rhs1
(49. Lgb)
(50. Rbg)
There are 50 positions, but only 48 available on Realiser. Also there are some errors on that map, which I tried to mark as ()
Thanks for asking btw, I finally got arsed to thru these actual names in my Realiser, now I can make corrections to this manual page until there's official fixed one.
Its way too easy to mix up these channel names, but when I'm doing measurements I want to be absolutely sure I measure correct channels so I don't have to redo them.
Now, I remember that there's is also a channel map in the command server manual pdf on page 19. There are 52 speaker positions and its different...
Now I wonder which one I should look... *SIGH*