Port length help

[KyleBechtold 5,000+ posts]

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 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?

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[Kangaroux 5,000+ posts]

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 5,000+ posts]

I am entering what the sub will see before port disp as I don't know the port displacement

 

[Kangaroux 5,000+ posts]

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 5,000+ posts]

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 5,000+ posts]

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 5,000+ posts]

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 5,000+ posts]

Yeah you can. What's your target box volume & port area?

 

[Kangaroux 5,000+ posts]

This is what I did for a port since doing a long L-port would come in contact with the sub

 

[KyleBechtold 5,000+ posts]

3.5cuft after port for target box..

42-49 for port area 12-14 per ft

 

[KyleBechtold 5,000+ posts]

this is what I had in mind I didn't want to do it in sketchup since it takes a second

 

---------- 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 5,000+ posts]

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 5,000+ posts]

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 5,000+ posts]

up

 

[KyleBechtold 5,000+ posts]

alright so should I do...