[1] I'm just trying to describe the types of approaches.
[2] I don't know what we're arguing about. We agree that object based mixing exists. Are we just arguing over it being new or not? ...
[3] My main point was that mixes designed for Atmos like the Beatles Sgt Pepper fold down into 5.1 mixes that don't work properly on a lot of systems, though if a system has a reasonably strong phantom center ine middle of the room, a lot of the appeal of the effects of Atmos come though.
[3a] Four walls approach is a lot more compatible with less than ideal home theater sound systems.
1. I realise that you're just trying to describe types of approaches. You've created explanations and conclusions of your impressions of listening to certain mixes on your system and used terminology to describe those conclusions. The problem/danger, is falling into the exact same trap the audiophile world so commonly falls into and for exactly the same reason. Audiophiles listen to mixes, get "impressions" and then create explanations and conclusions from those impressions using terminology. What usually results is confusion from misusing/misappropriating terminology and explanations/conclusions which are inaccurate (or just plain wrong) because there are other facts about the way things work and the way mixes are created which they either don't know about or are failing to consider. For example, it's perfectly possible to listen to a bunch of HRA recordings and gain the ACCURATE impression that HRA recordings are better than CD recordings and conclude that HRA is therefore superior to CD audio. We both know this conclusion is incorrect, this accurate impression can be caused for example by different masters and intrinsically there is no audible difference between HRA and CD audio. To a certain extent this is what's going on here, it's why we have a Sound Science forum and why I'm responding to your posts. For example: ...
2. We do agree that object based mixing exists but unfortunately, you are misusing/misappropriating the term, it has a specific and different meaning from the one you are using it for. What you are describing as "object based mixing" has existed since 5.1 was invented but "audio objects" and "object based mixing" has a completely different meaning and only exists in Dolby Atmos.
3. No, none of the effects of Atmos "come through". The only effects which can "come through" are those effects which can be created with 5.1. The only potential difference is that the 5.1 effects available might have been experimented with and employed more liberally than other 5.1 mixes.
4. The "four walls approach" you keep repeating doesn't really exist, it's just a term you've invented to explain your impressions and, it would be no more or less compatible with less than ideal home theatre setups.
[1] Blu-ray Atmos doesn't have as many channels as theatrical Atmos, [1a] which I think is capable of as many as 64,
[2] but in the average living room it should be able to make a significant improvement on imaging in the center of the sound field.
[3] Also, as I understand it, multichannel playback equipment has a built in ability to fold down mixes with more channels than the system has speakers, and to scale up using DSPs if the recording has fewer channels than there are speakers.
[3a] Again, nowhere near the precision of theatrical Atmos, but I have heard what is possible scaling stereo up to 5.1 using DSPs and it is a significant improvement.
[4] ... Both of these discs have lots of examples of sound occupying the center of the room and crossing from front to back and from one corner to the opposite diagonal corner.
1. Yes it does! Blu-ray Atmos has 8 channels (7.1), the same as theatrical Atmos. The problem here is that you are thinking in terms of the old paradigm, the paradigm that applied to all previous formats, which is audio channels routed to speakers. Dolby Atmos creates a new paradigm and you have to think about it differently or end-up making incorrect assumptions/conclusions! Atmos has the same number and function of audio channels as 7.1 but adds a new concept, the concept of "Audio Objects". Audio objects are certain sounds which can be designated as "audio objects" and are not recorded to any audio channel, they just exist as data/metadata. The decoder/processor then assigns these audio object directly to the appropriate speaker/s. In theatrical Atmos, the decoder/processor is in effect programmed with all the cinema's speakers and their position during installation and this is the real advantage of Atmos. If you have a small cinema with say 25 speakers or a large cinema with 120 speakers, the processor can intelligently work out for an audio object when and how to use a phantom position or point source position depending on what speakers the system has installed. So for example, let's take a sound panned to the centre position of a standard 2 channel stereo system. Obviously this centre position is a phantom centre but what happens if we add a centre speaker and a third audio channel? When mixing we now have the option of doing the the exact same thing, creating a phantom centre by recording the audio equally to both the left and right channels but we also have the different option of recording this sound to the third audio channel which is routed to the centre speaker. The advantage of using this second option is that we get an actual centre position rather than just a phantom centre but the disadvantage is that this mix is no longer compatible with a standard 2 channel stereo system, everything in that 3rd audio channel will simply be missing. Now let's apply the new Dolby Atmos paradigm to this example. We still have two audio channels but in addition we have the concept of an "audio object". When mixing we can still use the two audio channels as we would with a standard stereo system and pan our sound as a phantom centre but if we want, we can assign this sound as an "audio object" (which is not recorded to any audio channel/s) and pan it to the centre. What happens then is that the decoder/processor knows whether your specific system has an additional centre speaker or just a stereo pair and on playback routes the audio object (our sound) to the centre speaker if there is one or applies the panning law and routes it to the left and right speakers equally to create a phantom centre if we don't have that additional centre speaker. From this somewhat simplified example, I hope you can now see that if you've only got a stereo two speaker setup, the end result is exactly the same, regardless of whether you mix using the "audio object" paradigm of Atmos or just a standard stereo mixing. The real advantage of Atmos only makes a difference in cinemas, large spaces with loads of speakers. Of course, this explanation of Atmos ignores the height info, which is also an advantage/improvement over 5.1/7.1 but that's all folded down when reproduced on a 5.1/7.1 system anyway and I've ignored it to make the explanation simpler.
1a. Without looking up the specs again: Dolby Atmos has 8 audio channels, up to 64 audio objects and (if I remember correctly) can address a system of up to 128 speakers. But remember, the paradigm of audio channels and speakers is quite different with Atmos.
2. No, it won't make any difference to the imaging of the middle position of the soundfield.
3. That same fold-down ability (from say 5.1 to stereo) is exactly the same as what Atmos uses. Atmos does not use the DSP upscaling ability found in some AVRs though.
3a. I have a somewhat different opinion of consumer upscalers. Some of the early ones just applied a big surround reverb to the stereo and more recent ones are more sophisticated, they attempt to deconstruct the stereo mix and extract elements which are then placed around the soundfield with some surround reverb added. With some material this more recent approach works surprising well but other times not so well IMO. Some people though just like sound coming from all around them and prefer even poor upscaling to stereo. It also partly depends on the acoustics and quality of the stereo system, how well the stereo system can reproduce the depth cues. None of this is related to Atmos though, there is no upscaling, extracting elements of the mix or equivalent DSP effects. The problem of extracting elements to route to additional speakers is bypassed with Atmos by not having those elements "mixed" in the first place, in effect they're stored separately (outside the mix) and then added to the mix on playback by the decoder/processor. This obviously isn't the case with a mix that's been folded-down prior to distribution.
4. That's just a mixing decision which has nothing to do with it being originally mixed in Atmos. They could have done the exact same thing in 5.1 or 7.1. Your point here resembles the HRA/CD example above, HRA recordings can sound better than CD recording but because of somewhat different mastering choices, not because of the difference between Hires and CD.
[1] ...It's an Elton John song where the guitar solos starts on the front wall and slowly walks towards the listener, ending when it is about 2/3rds of the way from the front to the listening position. That one was done for a 5.1 mix, not Atmos, so I know that it was possible before. But Atmos gives music producers the tools to do it in a controlled way if the home theater is equipped for Atmos blu-ray playback.
[1a] And if they do it for Atmos blu-ray playback, it will be folded down into the 5.1 as well, just not as tightly controlled.
[2] The Sgt Pepper mix was roundly criticized in internet forums for being "front weighted" and "flat sounding". On my system, it's the exact opposite. I hear depth and sounds within the room. But I can imagine that systems where the front speakers are full range and the rear speakers are small, and in systems where the front and rear speakers are so far apart that they don't reach the middle of the room, that would sound pretty much front weighted and flat sounding. It didn't help that they had a mastering error that attenuated the rear channel -6dB.
1. No, Atmos does not provide the tools to accomplish that effect in a more controlled way, neither for a home theatre nor a cinema.
1a. The tightness of control you end-up with should be exactly the same as if it was just mixed in 5.1 in the first place, although it is possible under certain circumstances that the folded-down Atmos mix would be less "tightly controlled"! Again, your impressions are the result of mixing decisions, not the format (Atmos) itself. Most likely what you're hearing is the result of more effort, time and money being spent to create the Atmos mix.
2. If there was a mastering error with the rear channels being -6dB then the criticisms were justified, it should sound "front weighted and flat"! The fact it doesn't sound like that on your system indicates that your system is incorrectly calibrated, your rear speakers are too loud.
G