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.
It's not that they're optimal, but until recently outside a Trinnov, very few AVR/AVP models offered more than 11-channel operation. Thus, it has been born more of necessity than any kind of optimal setup. There are a lot of people excited about the newer 15-channel AVRs that are just now becoming available (outside a Trinnov that costs the price of a mid-sized sedan). More speakers means more precise imaging for more seats in the home theater. Without those speakers, seats that are off-axis won't get as accurate placement of many sounds due to the
precedence effect, whereby sounds tend to pull towards the nearest speaker when you're not centered between a given pair. So while your home theater may sound great to you in the primary seat, I think you'll find it sounds quite different if you sit off-center. That is precisely the reason I have front wides and surround#2 speakers in my 3-row home theater. That keeps the surround effects from pulling as much to the left or right and imaging from moving in straight lines over head (keeps them in a circle around all seats). In other words, those speakers aren't actually needed for the MLP, but for the other off-center/off-axis seats.
As for overheads, without top middle, front-to-back overhead effects will similarly pull to the nearest overhead speakers (front-to-back) that you're sitting underneath. So say a sound is meant to be directly overhead in the middle of the room. If you're sitting closer to the front tops speakers, it will image towards those speakers instead of the top of the middle of the room and the opposite for the third row. Only the seats directly in-between will image properly. That is where Top Middle speakers fix the imaging as it creates an anchor point in the middle of the room the same way a center speaker keeps centered screen effects and dialog in the middle of the screen even if you sit to the left or the right. Without it, the dialog will pull towards the left or right speaker depending on whether you're sitting left or right of center between the main speakers.
Thus, the more speakers the better for proper imaging for all seats as the more discrete speakers you have, the less effect the precedence effect has on the imaging for any given seat. Again, this is not for the benefit of the MLP, so if you're the only listener, you don't need them. But if you have a lot of people in your home theater watching movies, those people sitting off-axis aren't getting optimal experiences without more speakers. That is why high-end Atmos home systems offer up to 34 speakers (plus subs).
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.
It doesn't "really" require any such thing. A good installer can make many rooms work well. Some will need more work than others. A custom room should probably have the speakers behind a transparent audio screen, for example and hide all the wires, use drop ceilings, etc. to make it classy looking with custom lighting and all that. I've seen some pretty "wow" rooms done this way. That doesn't guarantee they sound "better" than a well done retrofit, however. Moves aren't about watching the drop ceiling back-lit or star fields on the ceiling, however cool it looks.
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.
Something tells me you have also never sat in any seat but the MLP either or you'd notice the 360 degree sound field fall apart for the same Atmos demos. It's not possible to do four rows of seating and maintain the surround field where it should be for every seat with only 11.2 speakers. As soon as you sit off to the left, center height effects will pull to the left top Atmos speaker and surround effects that should travel through the middle of the room will pull to the left side of the room, all due to the precedence effect. That's precisely why the "extra" speakers in Atmos and X exist in the first place.
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.
How odd my 17-channel system manages to work just fine, but then I don't "triamp" speakers (particularly since they are all 2-way speakers to begin with). The way I "slice it" is to not waste money on bourgeois tri-amping and custom ventilation systems (my air conditioning system functions just fine for the entire 12x22x8.5' room). Oddly, I cannot hear any "hiss" from the seating despite 17 channels of operation.
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.
Now I think you're just being overly dramatic. If my 17-channel system works fine in a 12'x22'x8.5' room, I don't think even larger rooms would be
pushed over the edge. Any hiss decreases the further you sit from a given speaker. They do not all add together evenly.
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.
Sigh.
Putting 30 or more speakers in a domestic space is just not sensible or practical on any level. Actually it is daft.
Daft? Now you're getting insulting. I know people with maxed out Trinnov systems. They seem to like their systems just fine and don't bugger on about how it shouldn't work because someone out there wants to pat themselves on the back and tell everyone his system is the best it can possibly be which it clearly isn't outside your MLP seat and I can say that with 100% confidence without having heard a bit of it just by your speaker arrangement.
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.
I suspect someone should have kept their opinions to themselves before they dove into the deep end. Your home theater does not work well with only 11-channels and 3 rows once you sit off-axis. That's a FACT (again without hearing it because I know about the precedence effect and it's clear you do not). Home Atmos is not "professional audio" nor is there some super skill into arranging a room of speakers with given angles offsets. I use 10 speakers plus the center channel which means 36 degrees between speakers would be optimal for an even rendered 360 degree circle. Oddly, Dolby's specs are within a 2 degrees of that using 11-speakers in their 11.1.8 diagram.
