So, just found this thread, and it's going to be a lot of help!
I'm a long-time AVS member, and enthusiast. I've finally built a home where I will have a dedicated theatre in the basement. The room will be about 20'x20' with 9' ceilings. I'm beginning the design phase for the system. My plan is to focus on movies, with a 2.35:1 140 " acoustically transparent screen, and hidden speakers for a 7.1.4 Atmos system. I had been thinking about trying to find some good prices on use JTR, or similar speakers, but have now been leaning toward DIY.
I want to have a lot of head room. I like to listen at reference type levels most of the time (100-105 db). And would like to have all 11 of the speakers be able to keep up with it. I also imagine keeping common tweeters across every speaker will be important (unless the ceiling speakers really have limited frequencies from ATMOS). The front LCR will be behind the AT screen, the 4 surround speakers will be hidden in false posts, or recessed in the walls, and the 4 height speakers will be in the ceiling (probably a drop ceiling for future proofing).
For the subwoofer, I have behind the screen a 42" wide x 18" deep x 9' tall concrete cavity that would just need a top and baffle on the front to have a super rigid subwoofer enclosure, right in the front of the room. I've built several transmission line and ported boxes in my youth, so I'm licking my lips at the thought of what I could do with the space, but honestly don't have the time to design/plan it (or develop the base of knowledge for doing it competently.
Please let me know if you'd be willing to help point me in the right direction for speaker selection/driver selection. Ideally, I'd buy flat packs and have Mig do the crossovers. I tend to not like bright speakers/tweeters, and find myself drawn to horn tweeters (HSU HB-2 for bed room speakers), ribbons, or soft dome. Ideally, I'd like to spend $400-500/front speaker, and $150-250 for surround and ceiling.
For amps, I'm planning on going with separates and balanced inputs from a processor. Maybe used Emotiva amps (or similar) and an Onkyo/Marantz refurb processor with Atmos and DTS:X upgrade.
Thanks for your time.