Rick, the relevant distance should be measured from the center of the woofer cone, also counting the distance traveled along the front and/or side of the enclosure.
So if somebody states their 17" deep 80's are placed 6" from the back wall, in reality they are 23" from the back wall and should be stated as such?
My primary reason for asking the original question was due to the equidistant issue regarding back and sidewall placement, in my warped mind I view the rear port as a sonic source from the speaker and try to integrate that into the placement of the speakers, but with a 17" deep speaker one can understand where there could be confusion with just exactly where the reference line should be regarding back and side wall placement.
It has always been one of those little nagging questions that often comes to my mind whenever I get into the measuring mood.
