i have to build a box for the first time without any dimensions and i am sooooo lost. i have built boxes before, but always had dimentions to start with and i added an inch here and subtracted one there etc etc. i have all the info on the sub and was curious as to weather or not anyone would be willing to help me out. it is an enclosure for 2 12" woofers and i want it to be a slot port with individual chambers.airspace req is 1.3 cu ft it only gives specs for a round port (another of many things that is making this difficult for me)port diam. is 4 in at a length of 13.5 inches. if you feel like helpin me out thanks if not well.... thank you too. the box is going into a tahoe so there is plenty of room for the box, the customer has the car so i dont know exact measurements but like i said if you guys can give me a starting point i can modify the design.
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Here's a starting point: figure the square inches for a 4" round port opening and convert it to the rectangle of your choice. Use pi R^2 to calculate the area of a circle, so the dimensions you have to work with is a 12.56 square inch opening that is 13.5 inches long. Now all you have to do is decide what size slot opening you want that will come to 12.56 in^2, and leave the length as it is. So decide what the longest side of the slot should be....let's say it's 12". 12.56 / 12 = 1.047, just a hair on the big side of one inch in width. If you want wider width, use less slot length such as 6". As long as you convert the circle to an equivalent square inch opening, the length of the port will remain the same.
Here's a link to an MTX box that has dual chambers and the slots share the common wall: https://www.mtxaudio.com/caraudio/products/enclosures/sledgeHammer8500.cfm
To find what size to make the box so that each chamber is 1.3 ft^3, here are the basics:
12 x 12 x 12 = 1728 cubic inches = 1 cubic foot
1.3 cubic feet * 1728 = 2246.4 cubic inches.
Find three measurements (in inches) that when multiplied will arrive at 2246. ( ex.: 15 x 15 x 10 = 2250). Add volume for port structure and driver displacement, using these guidelines, so that the overall dimensions will net 1.3 ft^3 in each chamber after deducting the driver and port structure.
Then make the chambers mirror images of each other.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.