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KyleBechtold
07-25-2011, 09:39 PM
hey I was looking at doing a slot port out the top of a truck box. I have a 4.36 box before port and so 12-14sqin of port area is 52.32-61.04.. My max dimensions are 3in(was 4.5" but .75" wood x2 =1.5) and I made the rest of the needed area up by making the other 20"... Well in Port calculator (http://www.carstereo.com/help/Articles.cfm?id=31) it makes one height and one width.. the thing is when I change to 3 to height and the 20 to width the required length is different so if the port is on top which is which?

Kangaroux
07-25-2011, 09:41 PM
It shouldn't matter which you put in what input field. Have you tried keeping slot port set to "no"? And are you sure you're entering in the net volume of what the sub will actually see?

KyleBechtold
07-25-2011, 09:45 PM
I am entering what the sub will see before port disp as I don't know the port displacement

Kangaroux
07-25-2011, 09:48 PM
The length is gonna be messed up if you don't put in the accurate box volume. What I find helps is, if you are using something like sketchup, is to first make a box your target net volume. Then from that, calculate port and add it onto the box. It takes away a lot of the back-and-forth between calculating port and what actually fits.

KyleBechtold
07-25-2011, 09:48 PM
alright so I did it as "no" on the slot port and it now requires me a length of 34.81" so my question is.. I know in a slot port the second wall can be part of the length but in a square vent can you add walls inside of it to extend the length?

Kangaroux
07-25-2011, 09:50 PM
alright so I did it as "no" on the slot port and it now requires me a length of 34.81" so my question is.. I know in a slot port the second wall can be part of the length but in a square vent can you add walls inside of it to extend the length?

The port should be a minimum of the smallest value in the port area dimensions from the wall. For example if your port is 4" x 20", it shouldn't be any closer than 4" from the wall it's perpendicular to. If it's close like that you can count it as being part of the port.

KyleBechtold
07-25-2011, 09:56 PM
The port should be a minimum of the smallest value in the port area dimensions from the wall. For example if your port is 4" x 20", it shouldn't be any closer than 4" from the wall it's perpendicular to. If it's close like that you can count it as being part of the port.

My box is 26.5" tall.. the required port length is 33.45" to be exact.. besides sticking out of the box 7"+ can you add walls inside the square port almost like a maze inside the port to make the length longer?

Kangaroux
07-25-2011, 09:56 PM
Yeah you can. What's your target box volume & port area?

Kangaroux
07-25-2011, 09:59 PM
This is what I did for a port since doing a long L-port would come in contact with the sub

http://i.imgur.com/BIKo2.png

KyleBechtold
07-25-2011, 10:01 PM
3.5cuft after port for target box..
42-49 for port area 12-14 per ft

KyleBechtold
07-25-2011, 10:04 PM
this is what I had in mind I didn't want to do it in sketchup since it takes a second

http://i438.photobucket.com/albums/qq101/KyleAndrewBechtold/porthelp.jpg

---------- Post added at 09:04 PM ---------- Previous post was at 09:03 PM ----------

that is the front of the box subs firing forward port up.. you can see through the box at the port but its working its way up

Kangaroux
07-25-2011, 10:05 PM
If you bring down the 20" dimension for your port around to 15 (thats 45 sq. in of port area, 3.5 cubes is ~42 sq. in minimum) then you cut down 10" on your port length if you are aiming for 33hz.

KyleBechtold
07-25-2011, 10:25 PM
even if I tuned to 33hz and did 3x15 it still would require a 24.81 height which would only be 1.xx off the bottom..

KyleBechtold
07-26-2011, 08:47 AM
up

KyleBechtold
07-26-2011, 01:06 PM
alright so should I do...
http://i438.photobucket.com/albums/qq101/KyleAndrewBechtold/porthelp-1.jpg
http://i438.photobucket.com/albums/qq101/KyleAndrewBechtold/porthelp.jpg
http://i438.photobucket.com/albums/qq101/KyleAndrewBechtold/porthelp2.jpg

Kangaroux
07-26-2011, 01:10 PM
Yeah you can do that. If you can, I would put a 45 in that corner there as it will help with the air movement quite a bit

KyleBechtold
07-26-2011, 01:17 PM
Yeah you can do that. If you can, I would put a 45 in that corner there as it will help with the air movement quite a bit

you are talking about the bottom right corner at the port correct? and which would be better? getting the length out of making it an L or adding the the maze type walls inside the port?

second question.. the bottom of the box is wider that the top as it is a wedge.. Should I make the port expand on its way down or make it the same length and width down? the reason I was thinking to expand it is so that the whole side acts as the port vs the port being on that side and there being space around it..