Found this post on avsforums about THX RE-EQ I thought it was interesting.
"With regards to Re-Eq, movie soundtracks are mixed "hot" in the upper frequencies to account for what is known in the industry as the X-Curve. The X-Curve is defined in ISO Bulletin 2969 as pink noise that is flat to 2khz and dropping 3db per octave as measured from 2/3rds of the way back in the theater. Because of the difference in size between the movie theater and the average livingroom, such a soundtrack would be perceived as being excessively bright. THX's Re-Eq flattens out the response curve for proper playback in the home. So, without Re-Eq, it wouldn't be "as the director intended" in the home environment."
