speaker distance settings effect on soundstaging

I was experimenting w/ the "speaker distance" settings on my Yamaha pre/pro for my center ch and left/right mains. My sitting area is 12 ft away. However, to me, it seem that if i put the distance setting on the yamaha to 14-15 feet the soundstage is much better, action from left to center to right main is much more transparent. The sound now seems more fixated to the video image(56" samsung dlp).

What actually happens to the audio signal when i do this? Is it a suppression of the sound? I figured that fellow goners could educate me on what i am actually doing to the soundstage. thanks for any possible info.....
It should only be a time delay to account for the distance. However, what you may be hearing is the difference between no delay processing and added delay.