I'm kind of stumped here
 

I want to build a sub box for my 6.5" AVI SL-170 (http://www.avisound.com/pdf_files/SL-170-SP.pdf) driver. On the data sheet it says I need a 9ltr or 11ltr vented enclosure with a 2.5" by either 13.8" or 11.8" port. When I go to the DIY Audio and Video speaker box volume calculator/designer page it says a box made from 3/4" material 10.5x10x10" with a 2.5x11.8" is 10.9ltrs. Great! My question is how do I fit a 2.5x11.8" port in such a small box staying one port width away from the sides and the driver which is what I understand I need to do? Or am I totally out to lunch and don't have a clue and I need to build a totally different enclosure? If so what would the experts here recommend? Thanks for any help you can give me.

Well this is an interesting one. A 6.5 inch woofer is not going to need a 2.5 inch slot port. At least I cant imagine that. From my experience a 10 or 12 needs a wide port like 2 to 4 inches. To reduce port noise. The way it works is the wider the port the longer the port. But let say it does. I think the problem lies in your cube design. I think they intend for this speaker is designed to work in a car door. So can you create a design that is slim and long? You might be able to have a really long port that way. If not I would recommend a round port design. You might be able to get a small diameter that goes all most all the way to the rear wall or maybe even a 90 degree turn inside the box?

Hi Fathershelper,
Thank you for your reply.
It probably was designed to go in a car door but the problem is I drive a Jeep TJ which does not have enough depth to fit the speaker. I found a box design for a 6" driver on another website which I built and am using now.
It isn't perfect, even my old and very abused ears can tell that but it works good enough for me right now. I am thinking of using the driver in a rear door of my wife's Ranger when I get around to putting a better stereo in it for her and trying something new for the Jeep.
In that application I think I have enough room for a round and long port. I sure wish AVI would have given better guidance on this driver on their website instead of assuming every buyer is an audio expert but it is what it is. Thanks again for your reply.