Still slow site response, but I have to respond (having Auro-3D with 11.1.6)
I've played with numerous configurations with or without "top middle" (acting like a dual VOG "middle" in some respects) and also shrinking the room down to effectively half size (moving rear height to "top middle" instead with only side surrounds). Let's call that "small room" with Auro-3D and Atmos and X.
Small room with heights.... Works fine. FULL overhead sound on ceiling. Think of it this way. It will pan between the front/rear heights at whatever height level they're at. If that height level is essentially on the ceiling (even if at 30/150 angles), it still PANS in a straight line across that height "plane" (an inch or two from the ceiling). There is effectively NO DIFFERENCE from "tops" speakers in this size room except that the sounds start next to the screen instead of 1/4 the way out into the room.
Longer room with heights. Once you get past a 120 degree angle (perhaps slightly less or more depending on how tall you are and other factors), the "directly overhead" (90 degree elevation straght up) starts to come apart like you're sitting in a gazebo blocking sound above you. This is what people who think "heights suck" are probably experiencing. Their rooms are too large for height speakers without option #3. the same thing would eventually happen with tops speakers also if you lengthen the room even further (say a 40 foot long room). It's just the angle between the two sets of speakers relative to your ears that limits the phantom imaging directly overhead.
OPTION: Add "Top Middle" speakers. This bridges the distance in either case. It's MORE effective, IMO with heights than tops in most home rooms simply because they need them more. Note that if you mount tops at 45 degrees relative to ONE row of seats, it will always pan fine overhead because the distance apart between the two is small enough to work fine. But you can't cover 4 rows of seats with two sets of ceiling speakers 45 degrees apart. It just won't work. Thus, it's the same problem as the room gets larger. This is why cinema Atmos has many many overhead speakers and why home Atmos has up to TEN speakers overhead (that's enough to cover like 6-12 rows depending on the spacing. You can go further by adding matrixed pairs (20 sets of overheads). That could get you up to 24 rows I think or 10 rows of really comfy recliners).
In any case, heights + top middle (or VOG) = direct overhead sounds work fine. For longer rooms, you will want surround and rear heights (copied) for Auro-3D to give full coverage (same for rear bed surrounds if you don't have a 13.1 Auro capable system). I use my surround heights PLUS the rear heights by extracting the surround heights as a "middle" point (like top middle) instead and that stretches it across the entire room (24 ceiling). Copying the rear height to surround height also works fine for all three rows (sounds pretty good, IMO).
Auro-3D movies handled like THAT are great sounding. Atmos is only slightly better in my room with 11.1.6 (Auro uses 9.1.6 here). With 13.1 Auro, it would sound as good or better than Atmos 7.1.6 up to 9.1.6 as it pretty much covers the same range (plus the options of center height and VOG to "lock" the sound into place for off-axis rows (something Atmos CANNOT do!)
Auro-3D music doesn't use direct overhead much (most music albums don't employ the VOG channel) and even with an extracted top middle, little goes up there. They're just not mixed (or recorded in the case of dual-quad miked recordings) that way. I mean how many instruments are on the ceiling in a concert hall?
Even some true Auro-3D movie mixes (like Death Machine) have a more "wall of sound" type mix (thunder was directly overhead in that movie, most most other scenes were wall to wall sound instead). Other movies like Flatliners sound JUST LIKE the Atmos version with voices wandering all over the ceiling in pretty much the exact same places!
The other thing I would address is Atmos not being good for music with ceiling speakers. I think this is because some home Atmos systems have "too much separation" between bed and overhead speakers. You get the same kind of gap mid-wall as you get with heights directly overhead if there's too much distance to the ceiling (e.g. a 10 foot ceiling might have issues with ear level speakers at 3.5 feet or something; I can't be sure of the exact numbers needed since I haven't heard them in person, but at some distance it will do that. You'll have ear level and overhead and little in-between. With heights and ear level, you typically have a nice smooth transition between the layers to the point where you can't tell where one ends and the other begins assuming the speakers match well. But then you might have the direct overhead issue without top middle added so....
The bottom line is that "perfect" Atmos needs more than 11-speakers in a larger room. For small rooms, 11 is probably enough for a nice ear to ceiling bubble, but then in that sized room heights and tops will both work. As the room gets larger, you have to pick between priority with that many speakers (strong overhead or smooth transition with full ceiling coverage). Add more speakers and you don't have to compromise.
The full ceiling is another matter. If you go with tops in a 24' long room like mine, you end up using only 12' of the ceiling! (25% to 75%). That's only HALF the ceiling! (compared to the entire length of the floor). Think about it. You've got front, side and rear speakers in 7.1 beds (and front wides in 9.1 plus an extra side surround in 11.1) to cover that entire 24' length. Now you want to cover the entire ceiling with only 4 speakers? It won't work! So to get the strong overhead, you cut out half the ceiling to get around it! But add top middle with front heights and you get the FULL 24' length with smooth imaging (not counting the "special" center speaker case, it's then even again! 6 bed and 6 overhead! You now have a helicopter that can circle high or low or anywhere in-between without limits. Using only tops, it can only fly 1/2 the ceiling! That's why I went with 6 overhead. The helicopter sounds pretty much identical at bed level (you can do this shutting off overheads and playing the same demo) and ceiling level here. It circles the ENTIRE 24' room length! That's the way to go, IMO.
We need more AVR/AVPs to support it (unfortunately locked Atmos is a problem; DTS:X Pro will soon solve it for everything else on models supporting 13+ channels).
You might be right about needing six ceiling speakers for a four row theater. However when I researched this for my room the consensus seemed to be that for most domestic situations four ceiling speakers is optimal.
Now unfortunately most domestic spaces are not really optimal for multi channel audio. It really does require a custom built room for optimal results. Few have that opportunity.
Fortunately I have had that luxury to design a room with almost perfect dimension ratios.
The room is 29' long with 9' ceiling.
So I did the layout to Dolby specs. It is 7.2.4. It is a three row 9 seat room.
Now the first row needs to be at least 12' from the screen and front speakers.
That being the case the front Atmos speakers are just in front of the front row, and immediately to the left and right of the outside seats.
The second row of Atmos speakers is in line with the first row, right between the second and third row. That second row is about 6' ahead of the rear backs.
In practice this has worked out well. The results from the Dolby up mixer has been excellent. I have no complaints with movies, they are terrifyingly realistic. I have never localized to an individual speaker. There seems to be an excellent 360 degree sound field with height illusion.
Personally I was highly skeptical of this new technology, but have to admit it works far better then I anticipated. All speakers seem to be a distance apart where a seamless sound field can be created but not so close together that they interfere with each others FR. Form my observation and measurements I can see why another two ceiling speakers might well be a downgrade.
The other issue in the relatively confined domestic situation is the downside of adding more channels. Even the very best systems make a bit of noise. So as you add channels then you downgrade the S/N of the system. So you have 11 audio channels plus the sub/LFE channels. So at a minimum for a system like this you are going to have 13 amp channels. In this system because of active triamping of two speakers and active biamping of three, the number of amp channels is 18.
Anyway you slice it that is a significant outlay on power amps to say the least, to say nothing of the power bill, space required and the design and implementation of the necessary ventilation.
So with the power amps and active crossover on alone, the room is quiet and no improvement in S/N would be required. Add the pre/pro in the mix, and you can just hear noise in a very quiet room. It does not ever intrude in program. However you can see that adding further channels would probably push things over the edge.
So I think for the size of a domestic room we are at the realistic limit now, unless we go to more expensive electronics with improved S/N beyond the weighted 100 db.
That is the S/N of each channel in the pre/pro. The power amps are 105 db unweighted, which is why you do not hear them.
Putting 30 or more speakers in a domestic space is just not sensible or practical on any level. Actually it is daft.
So my view is that 11 audio channels and 2 sub channels works very well indeed for a properly spaced three row cinema. I can see that 13 audio channels might be required for a four row theater. After that you are getting into the realms of professional audio.
I suspect the number of domestic AV rooms of the size of this one is very small and ones greater then 4 rows is likely miniscule.
