Well on my first attempt at designing it I had the port length right but I was measuring it wrong. I took one of the free box plans and re wrote all the values to what I need them to be to show my plans. So some of the proportions are a bit off but it should show my point.

I get 30" for port length this time because the box is 25" deep so subtract .75 for the back wall and get 24.25". Now since the port is 5.75" wide subtract that from 24.25" to get how long the first port wall should be = 18.5". Then I subtracted .75 for the front wall and .75 for the port 2 wall and got 17" for the actual piece of MDF. 24.25"- 18.5" = 5.75. Then divide that by 2 for the middle point of the port= 2.875. Add that to 18.5 and get 21.375".

Now for the second port wall I took my total target length of 30" and subtracted 21.375 to get how much more I needed. 8.625" is how much more is needed. From that subtract 2.875" for the middle point of the port. You get 5.75". So the length of the second port wall would be 5.75".

The picture should show everything if my wording of all of that confused you. Before I was getting my port length as wall 1 + wall 2, so it was pretty far off. Anyways after sub and port displacement I get 5.86 cu ft tuned to 33.49 hz.

It would be great if someone could look it over and make sure I am doing the port length and displacement right this time. Thanks.

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