This is another one of my hobbies... I do atleast 6-7 a summer outdoors.. Its awesome.
I've never projected onto a block wall, but I really don't think you will see the lines in the block. I've put my screen up with wrinkles all through it and once the movie starts, its not noticed. I've had people comment afterwards when its time to take down and they couldn't believe the wrinkles in the screen. If its not white already, I'd try to paint it, but its not even that critical. You could even get a bed sheet or painters canvas and project onto that as well.
You will need a projector with good light output if you want to hit a screen size that big. Many business class projectors have a high lumen rating since they are meant to project with some backlight in the room. If you have a projector, check out this website to see the specs and also calculate the throw distance/max screen size.
http://www.projectorcentral.com/projection-calculator-pro.cfmMy normal screen is 8'x10' inflatable. I do have a cloth screen that is ~10'x20' which is the max my projector is supposed to do. I haven't used it yet because I don't have any place to mount it yet.
Sound system.. I started out with a stereo and a set of good bookshelf speakers. It worked great. Since then, I've upgraded to a pair of 12" powered DJ speakers run through a preamp.
DVD player-- I use my Xbox most of the time.. We usually end up playing games after...
Backyardtheater.com is a good resource and a great forum.. Its probably close to as friendly as this site. If you look at the gallery on that site, you will see a picture of my original setup - under Bubba.
