Atmos sound objects positions above your head are defined by some included data in the audio data stream and how that are interpreted are done in the DSP in the AVR, how much of the sound that will go out to each speaker to place the sound objects correctly in the room. So it depends of what the AVR manufacturer have decided where you should place your speakers. Not following the user manual will slightly shift where the sound are heard and will not perfectly match what the sound engineer where hearing when he did his sound mix.
What does the AVR
manufacturer have to do with the original mixing room setup and what he heard? Unless their decoder is broken, it's the Dolby guidelines that should be followed, although frankly the Trinnov guidelines are much better to explain optimization for multiple formats, multiple rows and generally realistic expectations rather than some ideal number some Dolby guy came up with for the home that somehow oddly doesn't remotely match their cinema setups for surround versus overhead placement (i.e. cinema surrounds are often much
much higher on the wall than "ear level" and seem to be designed to circumvent the Precedence Effect by using the ceiling speakers to localize sounds across the rows for multiple people (something that simply cannot work properly for off-center seats with just two surrounds on the far walls). Perhaps this is why so many Atmos soundtracks lack distinct ceiling objects as they are meant to be blended in a cinema to overcome stereo left/right imaging limitations in large rooms rather than just height effects?
It should be noted that no two mixing rooms are identical either (the studio guidelines have a LOT of leeway for speaker placement, going as low as 15 degrees for "Height" speakers, for example (compared to the original 30 degrees minimum at home, followed by the updated 6+ overhead change to 20 degrees) or as high as 55 degrees for setups using only "Tops" speakers (there's no way a Height only or Tops only setup is going to get mixed the same;
ideally a mixing room should have at least 9.1.6, if not 11.1.8, IMO) so there is literally no way to know
exactly what some dude in a mixing room heard or wanted, particularly when you're choosing whether to do 20 degree Heights + Top Middle versus 45 degree or even 55 degree Tops only. Which did the mixing guy optimize for? Who knows.
Worse yet, some soundtracks released only use "locked" or "pre-print" layouts and some only used 2 overhead channels at home (and there's traditionally been wide disagreement on here whether you're better off with 4 overheads or 6 overheads to deal with such soundtracks). We're assuming you're sitting at the MLP to match what the sound guy intended. Yet Atmos was designed for a large cinema audience, all sitting in different locations. Not everyone can sit in the perfect one seat in the movie theater and thus how can a cinema soundtrack be "intended" for ONE person? It
cannot.
Thus, I personally think many people place way too much credence on this fantasy notion of "what so-and-so
intended," which sounds good on paper, but we really have no real idea what that person was thinking or heard, let alone
intended. Sound mixes are all over the place and I doubt the people mixing these things
intended some of them to sound like a blurry mess, but then like any job, there's also flat out incompetence out there (as many a Disney
CrapMoist™ mix will attest). But I'm sure it sounds good to them in their minds.... Yes. My home theater is exactly as George Lucas
imagined it to be in 1977 (not what he actually saw/heard, but the fantasy magical version in his mind that lead to the god-awful edits of the original trilogy that should have been damn well left alone).
I think the best one can do is follow the guidelines that best matches the room requirements (rows, seats across) they're using combined with the number of processing channels they can afford and how many speakers they can properly place in their room. Again, I think the Trinnov guidelines are a good read to consider before planning a room/setup.
www.dolby.com
