Next you select two of the 36" panels and draw lines to indicate the center points for the woofer, tweeter, and port. The tweeters should be mounted asymmetrically, 1" off center. Here are the critical dimensions: 1) the tweeter cutout is centered 2-1/2" from the top and is 1" off the center line of the panel (be sure to build mirror image enclosures). The cutout diameter is 3-1/8". 2) The woofer cutout is centered 8-7/8" down from the top of the panel. The cutout diameter is 7-5/16. 3) The port cutout is centered 12" from the bottom of the panel. The cutout diameter is 4-1/4.