This is a rebuild for a box I built 3.5 yrs ago. The owner was so pleased with the sound it was brought in to repair water damage, after accessing the damage the decision was made to rebuild it and tweak the design using bassbox. The original frequency and volume was not changed but bassbox modeling showed the enclosure would be louder with one shared chamber(original box was duel chamber and two end ports) for all the subs and one port would be more efficient instead of two. Center ports for large enclosures take advantage of better airflow and free bracing offered by the port walls. More upgrades for this enclosure include screws every three inches and two circle braces that connect the side walls to the port walls and bottom to top rigidity. Graphics and a 3/4" port flange finish off the exterior look.