1. ## Port length and size..I **** at this.

My box is going to be 30x20x17, sub firing up, aero ports (or tube, i dunno if aero is the actual name for them) on the bottom back of the box firing towards the back of the hatch...I'll prolly be ordering them off partsexpress, but I'm completely lost as to what diameter and length I should get for a tuning of 30hz? I'd like to have one on each bottom corner of the box..or just a big one in the middle? I have no idea what would work best..Any help would be appreciated, thanks!

2. ## Re: Port length and size..I **** at this.

http://www.the12volt.com/caraudio/boxcalcs.asp

Using that port length calculator, if I used 2 4" ports totaling an 8" diameter, if the box was 4.7ft^3 and if the desired tuning frequency was 30hz, the total port length would be 26.17", making 2 13" ports that were each 4 inches in diameter correct?

3. ## Re: Port length and size..I **** at this.

No, each port is 26".

As your port volume increases, so does its length.

4. ## Re: Port length and size..I **** at this.

Originally Posted by diatribe
No, each port is 26".

As your port volume increases, so does its length.
each port 26"? umm are you sure about that? what Zxcvtypo said about using 8" diameter and dividing the final port length by 2 makes sense.

5. ## Re: Port length and size..I **** at this.

Originally Posted by js09
each port 26"? umm are you sure about that? what Zxcvtypo said about using 8" diameter and dividing the final port length by 2 makes sense.
No, his way is completely wrong and illogical. First off, two 4 inch diameter ports are no where near the surface area of a single 8 inch diameter port.

Also, the more port area you have, the longer the port becomes. If you add more ports, you add more port surface area which means you need to increase the length. Adding all the lengths together does NOT give you the total port length.

6. ## Re: Port length and size..I **** at this.

its ok guys, i went with a slot port..and it slams, i'm happy

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