Atmos in 5.1.2: where does the top rear audio go?

[ar surround]

Dolby themselves refers to the 7.1.2 as the bed. This is correct terminology.

https://professionalsupport.dolby.c...rence-between-beds-and-objects?language=en_US

"A Dolby Atmos input bed can be 2.0, 3.0, 5.0, 5.1, 7.0, 7.1, 7.0.2, or 7.1.2. Distribution of the bed in the Renderer is defined by the number of speakers in a particular room."

Anyone else's head spinning right now?

 

[sjcorne]

Anyone else's head spinning right now?

I wouldn't get too hung up on the whole bed/object thing, as it's really inconsequential from the listener-end. We can't tell from listening to encoded files (either lossy DD+ or lossless TrueHD) on our home systems whether the engineer has used just the bed, just objects, or some combination of both - but sometimes you can make an educated guess based on certain mix choices.

The main disadvantage of only using the bed is that you're always stuck in a 7.1.2 environment, even if you have more speakers in your setup (7.1.4, 9.1.4, 9.1.6, etc). So if you're mixing on a 7.1.4 array and you pan a backing vocal to the top, it will stay suspended between the front and rear height speakers. You can only control its left/right position, not front/back. If you wanted a specific sound to emanate only from the front or rear heights, or just in one of the top corners, you'd have to use an object.

 

[himey]

My amp allows me to specify the physical location of my two height speakers, either front wall, front ceiling, middle ceiling or rear ceiling. Choosing one of these options controls what audio is actually sent to the speakers.

I have tested two Atmos receivers, a Yamaha and a Denon, and both of them ignored the front wall setting, and treated a 7.1.4/5.1.4 Atmos test signal the same as if you selected the two height speakers to top middle. All four top test signals came out the front height speakers and were not re-routed to any of the surround floor speakers. Dolby's advice for only 2 top/height speakers, is to place them above the listener, in the center of the room, as you noted.

I did the same test, with the same two receivers, using DTS-X, and the results were different, and as expected. When you only use two height speakers and set them as front wall height channels in the setup menu, DTS-X will send the rear two height signals in a 5.1.4 test clip, to the floor surround speakers in the sides/back.