I am looking to figure out port size for my project. I the port requirments are as follows:
(2) 4"x 10" ports per sub x (4) subs= 8 ports !Yikes!
I want to drop down to 2-3 ports tops. Can this be done and if so can someone tell me the size requirments.
You could look at making this a slotted port. You are also obviously using these subs in a common chamber. You should first figure out how you are going to constuct the box, how many chambers and how many subs will share a chamber. Each chamber will have to have a port. So...in the case where you put two subs per chamber, you can have one slotted port per chamber for a total of two ports on the project.
Use pi R^2 to find the area of a circle. pi = 3.14. R = radius of the circle.
One sub needs the equivalent square inches to two 4" round holes. And the depth remains at 10".
Two subs need the equivalent square inches to four 4" round holes...and the depth still remains at 10".
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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.
Here's how to do the math:
- pi R ^2 is 3.14 X the radius squared.
- The radius of a 4" circle is 2".
- 2" squared is 4".
- 3.14 X 4 = 12.56 square inches.
So the equivalent square inches of each circle is 12.56 inches, and since each subwoofer needs two 4" circles of opening, double that for 25.12 square inches. Four subs at 25.12 square inches of port opening each = 100.5 total inches for the project.
If using one slotted port for two subs, the slotted opening would have to be 50.2 square inches. The box will have two of these slotted ports for the total four subs. Since we just converted the opening size from round to square, you will not change the depth...so it remains at 10".
To find out what dimensions a 50 sq.in. slot should be, first decide on one of the two rectangle dimensions. Say you want the longest side to be 12". Divide that number into 50 to find the other dimension of the rectangle. ( 50 / 12 = 4.2 ) so the rectangle opening would be 4.2" X 12" for each pair of subs.
The tuning frequency will remain true to specs as long as you build the box with the amount of interior volume that is recommended along with those particular port specs you listed...making sure you deduct the total amount of space being used by the port structures and the subs, bracing, etc. As long as you keep the opening size equivalent you just leave the depth at the specified 10" for the same tuning frequency.
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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.