The dB loss you measure per doubling distance would be the same in any situation. Proper treatments will assist in a flatter frequency response within your room (bass traps, panels) however most people with properly furnished rooms will be fine. You will come to a point where you will rather just enjoy the system versus worrying about 1-2dB's which you can't perceive anyway.
The thing is, people on this site are saying 3db per doubling, and elsewhere it is 6db per doubling. At 3 meters, that can mean either 4.5db down or 9db down. 4.5dbs makes quite a difference, considering it can mean the difference between needing a 200W amp and a 500W amp.
Ah, another question I forgot to ask in the last post. How much headroom is generally recommended? Is 3db a good rule of thumb? If it is more like 1 or 2db of headroom, is that sufficient, or flirting with disaster? I mean, let's say I know I need 226W to get to 105. And I calibrate my system so that 0 on the volume knob is reference. Would getting a 250 or 300W amplifier be "safe", or should I really go for that 3db of headroom, and get a 500W amp?
I guess the real question is, how many movies have peaks above reference? Properly mastered movies should peak out at 105db... but it seems there is no shortage of movies with bad mastering...
