I've set up my home theater in an old room that was added to the house and there's really no sound proofing done at all. Last summer my parents came to visit and I was demonstrating my home theater to some friends and I put on The Lord of the Rings full blast just to show them how loud it could play (pants-dropping bass that's for sure!
). Anyway my dad went outside the house and stood right in front of the outside wall where that room is located and he barely could hear some thumping, nothing major; I had to check myself and I couldn't believe how quiet it was.
It's a little louder inside the house but definitely not bothersome. All in all I'm very satisfied with the results considering I didn't do anything to the room!
