I posted a short list of what I would change if I had known more in my build thread, but I should share it here:
- I went with a fairly large screen, hoping to get a little more height than a 120" and have a wider screen for movies. In theory it is great, and in reality it is great, but it also came at great cost. You can't just throw up a DIY screen or even a woven AT screen when you have a 150" wide screen, unless you have a light canon like a $60k Sony 5000es. You need screen gain to make it work with HDR, even with the excellent tone mapping that is available today with some projectors and processors, and screen gain over 1.0 in an AT screen means you go with perfed vinyl. Micro-perfed Vinyl has drawbacks, even if you sit the required 11 ft + back from it, and worst of all it is very expensive when you get to this size of screen. Simply going smaller on the screen and sitting closer would have saved a LOT of time and money. I could have gone with DIY spandex or a high end woven screen like a V6 Dream Screen and saved thousands of dollars just on the screen.
- Seating. Given that it is hard to sit in specialized seating before purchase, this one was particularly difficult to deal with. In my case, I started with Fusion seating, which is a good value for the money but the ones I went with lacked lower back support and the headrests were just too far forward for a front row. I put them in the back row and went with Palliser seats I had tried out a couple years earlier at a showroom in California when I was traveling. The problem is, Palliser custom makes the seats to your spec, and the level of stuffing changes from seat to seat, so the one in the showroom might be softer, and there is a fairly long break in period before they are more comfortable. Plus the showroom had the high end 3000 leather, and to save a few dollars I went with cheaper 1000 grade leather, which is WAY less flexible. The result was seats that are not nearly as comfortable as they were in the showroom, even after breaking them in and even after removing some fill from the seats. In hindsight I wish I had spent a couple thousand more on the better leather. And really, while home theater seats look cool, sometimes just a good old fashioned couch will work just as well at a fraction of the price. You sit there for 2 hours or more, and you need to be comfortable or you might as well just go to a public theater. Heck, get a few Lazy boy recliners, put narrow end tables between them, and call it good. Much more comfortable and really the big benefit of the home theater seating is having places to put your drink, snacks, and remotes without them falling between the cracks of the couch... Not easy to do when you have 4 across seating and you sit in the middle.
- Design. As mentioned in the post before this, having a complete, detailed design before you ever start building is a major time and money saver. I took the approach of getting a rough idea, build a house around that rough idea, and just wing it from there. I spent hours trying to solve problems and design it on the fly, and I should have done this ahead of time. It's tough for a DIY guy to pay someone to do the design, and for me it only cost me my time when I had to stop and ponder a problem before proceeding, but if I were paying a contractor to do it, it would have been very costly, so there is definitely value in having a pro do the design with details. When building a room that costs $15-20k in materials alone, a few thousand for a design really isn't too far out of a cost.
- Subwoofers. I caught some flak for saying this, but if I were doing it again, I would at least design the bass setup differently if not just scale it down. Part of the reason I went with 6 18's in large vented enclosures was to just try to tame the room by hitting it from all sides. It was successful, but in reality I use about 5% of what I have on "normal" viewing, and maybe 50-70% of the total in the most extreme situations. I had it jacked up higher but it was causing problems like cracked grout upstairs and making the projector move around on the shelf. It's fun, but not really practical. I would have been better off with maybe 4 subs and some MBM's or something... You just don't really need 125db+ at 10hz.
- Soundproofing. If doing it all over, I would either enclose the entire theater in thick concrete walls, or build a single level house so I don't have people above or below it. In both cases, I would go triple drywall with a full room in room construction. The fact is, soundproofing works excellent for frequencies above 100hz, and even fairly well down to about 50 hz. Below that, your DD+GG is like tissue paper, and when you have over 120db of 10hz making everything move, you might as well have just saved the money and not done any soundproofing. If I am going to go through the efforts again, I want it to work well enough to not hear a movie played at a normal volume to be heard outside the room. That would take a lot, I know, but anything less seems like a waste of money. I get all the reasons to do it, including making the room quiet to start, and that is great, but I can do 95% of that with acoustic absorption materials.
- Lighting. You can NEVER have too much, and you should NEVER leave it all on over night. Also, spend the money for better quality stuff. My LED strips in the ceiling degraded and I am now in the process of replacing them, which sucks because I didn't design it to be easily replaced. I prewired for full RGBW, which is good, but this is a lot of work to replace. I will eventually add wall sconces and reconfigure switches to be controlled differently, and thankfully I can hide it all in the ceiling and behind panels on the walls. Dark walls and carpet make for dark rooms in the brightest light. It is great for hiding the dust that collects in the corners and on trim, not great when you need to clean or fix something. And when you have a LOT of lights, they make a LOT of heat. My LED's are powered by supplies in another room, but they still get hot (the reason they are degrading), and the very nicely dimmable incandescent lights give off a lot of heat. I left it all on over night once and the room was over 90 degrees when I went in the next day. Oops.