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Message: <blockquote data-quote="mat3833" data-source="post: 7725589" data-attributes="member: 587645">to make this question simple i am going to just give a basic scenario instead of my actual problem. i have a box that is currently tuned to ~ 42Hz. it is a prefab HT box using a small 6.5 inch sub. with the current settup it performs VERY well except when a building falls or whatnot. it just cant reproduce the lower frequencies that well with its current tuning. so i decided to do some tests using some cardboard to add an external port to the box to lower the tuning and the results are fantastic. adding ~ 30 inches of port(port diameter is only 3 inches) has lowered the tuning into the low 30s to high 20s( tested using a visual method of measuring cone excursion and a computer program playing a steady tone) the only problem is i dont have enough room for 30 inches of port where the sub normally sits. so here is the question:can i make the external port LARGER than the internal port. if i take the 3 inch port and make it a 6 inch port i can effectivly half the required port and i can fit the sub where is currently is and still load the port properly in a corner load settup. BUT i dont know how the change i port diameter will afffect the airflow. i would be using a cone to adapt the larger pipe to the smaller one and using epoxy to secure the cone without leaving a "lip" on the insede of the pipe. then silicone will be applied to the interior of the joint to form a smooth transition, with the same thing being done to the cone-to-large pipe transition.how will the transition from a 3 inch port to a 6 inch port affect the enclosure? i plan to do a test with more cardboard(actually its a fiberglass reinforced cardboard sheet, pretty darn stiff and only ~ 2 mm thick.) to see actual results, but i wanted to get your opinions before i wasted my time.Matt</blockquote>

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