Originally Posted by audioguy
I left subs out of my comments. I have eight F18's.
So to get to your "sweet spot" I need to buy (if I were at 7.x.4) another 8 channel amp (in my case another ~$4500), upgrade to an Altitude 32-24+ (another ~$13,000), and buy 8 more speakers (in my case ~$12,000 in order to match tweeters and midrange drivers - one of my requriements). So for an additional $30,000, how much more immersive will it be?
We'll be happy to spend your money, Chuck. What are hobbyist friends for?
Seriously, we may also be caught in terminology. I think we both would agree that for 3D audio with Atmos or DTS:X, 7.x.4 is a minimal prerequisite unless you have a room that's so small that you can only do 5.x.4 with one pair of surrounds. Maybe what I think of as "sufficient" is what you call "sweet spot", which to me implies optimality.
Anyway, from my POV you don't so much lose content (something you're not hearing) with 7.x.4 vs. 13.x.8 as hear a particular Atmos mix with well-defined object passthrough as having more realistic - precision, a higher sense of dimensionality of physical presence - sound with higher channel count. If that's diminishing returns, so be it, but I could say the same thing about a 5.1 mix in native mode vs. one using speaker arrays, or upmixed with a high quality upmixer that doesn't destroy the soundstage. I just think it's better when it's possible.
Take these two Atmos examples: the movie Oblivion's scene in the giant cave with blast doors where Tom Cruise and the resistance are holed up, and the TET is sending a pod to exterminate them. With two pairs of side surrounds, I hear the pod moving inside my room between my wides, front side surrounds and bed side surrounds and vibrating subtly before Morgan Freeman's assistant shoots it down (if memory serves). That effect is exciting and helps to bring me inside the scene. Without the front sides it's more subdued. Or War for the Planet of the Apes, where in a battle scene, ape cries that stay within the center pan more from left to right using Lc/Rc when I tested with 11.x.6 (no Lc/Rc) vs. 13.x.6 (with Lc/Rc). And it's distinct from what I heard from the mains, that is inside the screen vs. just on the edges or just outside the screen with mains, from about 11 feet from the screen.
The question is cost, of course. Is it worth it? Only your wallet and your ears will know for sure. I didn't spend more than $500 to get my timbre matched Lc/Rc bookshelves as presence speakers for my own speaker manufacturer, and I had the available channels open. I wouldn't buy new amps and upgrade from an Altitude 16 to a 32 just to get that effect. But if it's possible for someone, I'd say at least think about it.
As for massive improvement, well, I know at least one guy (hint: he's from the UK, has a giant ear in his AVS avatar, and is allergic to Emotiva pre-pros
) that spent over $60K on his room and insists on staying with a Marantz, a MiniDSP running Dirac, and 7.1.4, no matter than he could easily afford a Trinnov setup and actually use his wides and top middles that he installed and wired but doesn't have connected to a processor that can render them. All is relative.