Port Length Forumla Help

[Lonewolf32 10+ year member]

I dont understand why you add 1.5 (1/2 of port width to connect to the middle going up). This is how I got it:

Your External Dimentions 30 x 14.5 x 19.5

19.5-.75 (board thickness)-1.5(1/2 port width)=17.25

17.25-25.5=8.25

8.25-.75(slot 1 bord thickness)-1.5(1/2 port width)=6

I dont think the 1.5 (1/2 of port width to connect to the middle going up) is right.

I could be wrong.

 

[berserker 10+ year member]

Okay what you are showing me makes sense, maybe somebody else can pitch in and confirm this as I am now questioning if I measuring the port length incorrectly. But now at least, thanks to you, I know that I was doing the formula correctly.

 

[berserker 10+ year member]

Okay so what you said got me thinking and I grabbed one of Moes Lesters designs to retest myself on how to measure port length and this is what I came up with.

18.75 - .75 (board thickness) - 1.75 (1/2 port width) = 16.25

34.75 - 16.25 = 18.5

18.5 - 1.75 (1/2 port width) = 16.75

But on that design it says that piece should be 15 inches long.

So where did the 1.75 go?

Now if you do it like how I do it, it works out.

18.75 - .75 (board thickness) - 1.75 (1/2 port width) = 16.25

34.75 - 16.25 = 18.5

18.5 - 1.75 (1/2 of port width to connect to the middle going over) - 1.75 (1/2 of port width to connect to the middle going up) = 15

or (if you already know your cut pieces)

13 + .75(baffle) + .75 (port piece 2s thickness) + 1.75 (1/2 of port width) = 16.25

15 + 1.75 (1/2 of port width to connect to the middle going over) + 1.75 (1/2 of port width to connect to the middle going up) = 18.5

And that is what I did before on my example, just added it up going from the beginning of the port. Because I already figured it out by subtraction to get my length for the port pieces.

Does this make sense, can someone clear this up?

 

[Lonewolf32 10+ year member]

Now you got me thinking. So I went to the JL website and found this

http://mobile.jlaudio.com/products_subs_enclusure.php?series_id=10

If you do it the way I do you get the 8.875" that they do if you do it your way you get 7.875".

 

[Lonewolf32 10+ year member]

Can someone clear this up for me are we both right?