Originally Posted by gmore
Obviously a tight space and a tough build. If you're looking to do an atmos set-up, not sure the reason for front height? If you're looking to maximize dts-x, than lots of options there(and I have little experience there). Not much I can add other than if atmos is priority, you will probably focus on couch as pll(unless love seat is very important) and keep spkrs aligned based on atmos posted guidelines and with 12' ceilings, maybe consider the 30-degree models(763l,ers610,ert) in-rear-wall facing down(for 4 matching atmos) with surrounds on side-walls as far behind couch as possible to complete a 5.x.4. This is me getting experimental(which I tend to do) but obviously your money and not sure there's a perfect answer here. Sorry, I know nothing about the AV123s.
The reason for front height is that I cannot install 4 ceiling speakers and still be within Atmos guidelines for proper ceiling angles due to the distance between the couch and the rear wall. Having a 12 foot ceiling makes getting the angles right a lot harder versus some of the shorter ceilings many of you have. It's impossible to get proper minimum angles on ceiling speakers behind the listener. I estimate I'll need at least 5 ft of distance between the MLP and the rear wall. I only have about 30 inches.
So the suggestion was to just do a pair of ceiling speakers at about 25 degrees forward of MLP (which is what Dolby guidelines suggest) using the C763Ls. Front heights were suggested by another person on this forum to replace the second pair of ceiling speakers that I cannot install. Dolby considers this to be a lesser solution (a holdover from the Dolby Surround IIz days) but it is a legal solution with most processors including my Marantz 7703.
It is possible to do a pair of ceiling speakers for "height front" and Dolby Atmos enabled speakers in the rear as a hybrid solution according to Dolby. But since the ceiling isn't completely flat (a barn style configuration) which may lead to unwanted reflections. I've cobbled together a DIY Dolby Atmos-enabled arrangement with a couple of old satellite speakers I have sitting on my front towers. It works....sort-of. But the speakers are small and I think i can certainly do better. The other problem with doing rear Atmos-enabled speakers is that if I sit them on top of the rear towers, the left surround speaker is really close to the MLP which would be audible in not good ways to the listeners on the left side of the room.
The idea of mounting a couple of C763Ls in the rear walls above and behind the head of the listener and tell the processor that this is a rear ceiling Atmos speaker is interesting....certainly clever. But true ceiling Atmos speakers usually work better with higher ceiling mounting in order to get a more diffuse soundstage. If you have a lower ceiling, Dolby recommends Atmos-enabled speakers and this was borne out in many of the early published reviews of Atmos theaters. In-wall C763ls in your suggested configuration would only be about 6-7 feet off the ground, which is too low to work effectively, especially working with a pair of ceiling speakers at 12 ft high off the ground.