1. ## Designing a ported box with George

So i notice some guys here need help designing box. well may i suggest you try and give it a shot yourself first? ill help ya

Step 1: Measure your trunk too see what your max dimensions are. Then subtract twice the thickness of the mdf your gonna use (usually 3/4" so subtract 1.5"). This gives you the internal dimensions you need for the upcoming equations. example, your max dimensions are 10" high and 20" wide so so your internal dimensions will be 10-1.5=8.5" and 20-1.5=18.5".

Step 2: Now remind your self of what internal box volume you need, pick a tuning frequency, and pick a port area.

Step 3: Figure out port length using this formula
Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2] - 0.823*sqrt(Av)

Lv is port length (what your solving for)
Av is your port area (height x width of the port face)
Vb is the internal volume of your box
Fb is the tuning frequency you want

Step 4: subtract half of your port width from your port length(Lv) to get physical Lv

Step 5: now you need to figure out how long your second wall is gonna be, so pick ANY number shorter than pLv. you can do this because your displacements always gonna be the same no matter how deep your box is.

Step 6: now take your physical Lv and subtract the external depth ( the number you decided on in the previous step +1.5" for the mdf. ex: if you picked 12 then your external depth is 13.5) from it. now this will give you the length of the 2nd wall.

Step 7: take this length (step 6) and multiply it by your port width+.75 and then multiply it by your internal height and finally divide by 1728. this gives you the displacement.

example, your 2nd wall length is 20", port width is 4", and height is 10"
so you get this 20*4.75 (since you need to add the thickness of the mdf to the port width)*10 for height/1728= .5497ft^3

Step 8: Now find the first wall length which is internal depth-port width. like in step 6 lets use 12. but this time since its internal depth we do not add the 1.5" for the mdf. example: 12-4=8. 8 is the length of your first wall. now do step 7 with these numbers to find the displacement. example: 8*4.75*10/1728=.2199ft^3

step 9: now find out how much your sub displaces by lookin in your owners manual or the company website. when you find out how much is displaces, well use .21 (15" xxx). so now you add all the displacements.

example: .5497+.2199+.21+(the internal box volume you chose earlier, well use 4 cubes) so the gross volume is 4.9796ft^3. this means your TOTAL box will be 4.9 cubes including port, this way your sub gets its reccomeneded 4 cubes (15" xxx in this example)

Step 10: Now we need to find out how deep we need to make the box in order for the sub to get its 4 cubes. well i know what your thinking...
"we used 12 inches for internal depth earlier in the example, how can it change now?" well like i said, displacement always stays the same so we just chose a number inorder to find the displacement, now we need to figure out how deep we need to make it to actaully fit within the 4 cubic foot reccomeneded volume.

so to do this we need to do the gross volume (step 9)*1728/(HxW).
example: 4.9*1728/(10x20) and we get 42.336. so the internal depth would be 42 inches for a box that is 10 inches high and 20 inches wide, in order for it to be 4.9 cubes total(gross volume).

Step 11: find the real port wall lengths.

for port wall one, its just internal depth-port width. example: 42-4=38" is your first port wall length.

for port wall two its your phyisical port length - (internal depth + 1.5")
example: lets say your pLv is 20 and your internal depth is 10 so you get 20-11.5=8.5". thats the length for your second wall.

and your DONE . now of course all the numbers in this post are screwed up cause i was just makin them up as i was going along and not actually tryin to make a box, so the numbers wont match. either way try it out. good luck!

2. ## Re: Designing a ported box with George

ttt for a good place for people to learn some things.

3. ## Re: Designing a ported box with George

Originally Posted by Jmac
P.S. I hate you
Jmac do u also hate me 4 the sticky??

didnt u c the STICKY on the BOX construction. place.
u could have just added ur info

4. ## Re: Designing a ported box with George

Originally Posted by Jmac
It should be noted that you still have to know what you're doing

I have a feeling it's going to be like when I posted this stuff and and people started complaining about how their enclosures sounded bad or kept PMing me to check over their designs ... I don't really have a problem with checking over designs, I just have a problem when I have literally a dozen or more requests a day to check over designs ... It was also frustrating because my actual design request count went down from about 2-3 a day to 3-4 a week ... So I basically went from making ~\$150 a week to ~\$35 a week ...

P.S. I hate you
just say no.

5. ## Re: Designing a ported box with George

Originally Posted by BASS OUTLAW
Jmac do u also hate me 4 the sticky??

didnt u c the STICKY on the BOX construction. place.
u could have just added ur info
i did...but i read over it and i still couldnt design a box. so when i learned i decided to post step by step with lots of examples and make it as easy as possible for the person to actually succeed.

Bump

7. ## Re: Designing a ported box with George

i havnt read this - seeing as im at work, but from the looks of it, its really in depth. ill have to give it a try. im planning on building a box for the next car i get (my dads) so i may try this out this weekend.

tune low + big port area + big box = loud as hell

ill post my thoughts on saturday when i give it a go. just gonna be rectangular with an elbow port most likely.

8. ## Re: Designing a ported box with George

Thanks for an awesome tutorial George

9. ## Re: Designing a ported box with George

your welcome. it should be noted that this is for L shaped ports. ports with MORE than 2 walls i did not write about. as soon as i have time, and i get help from a certain member of CA.com about how to do those again, ill post it up. but yea, this tutorial is easier with a little bigger boxes, and higher tunings.

10. ## Re: Designing a ported box with George

ok that is what i wanted to know too. was this tutorail for square shape ports.

11. ## Re: Designing a ported box with George

Originally Posted by LBX2G
ok that is what i wanted to know too. was this tutorail for square shape ports.
by square shaped ports do you mean "slot port"? like a rectangular front face, with the port wall runnin in and then turnin in a L fashion?

12. ## Re: Designing a ported box with George

yeah, slotted ports

13. ## Re: Designing a ported box with George

so am i correct .

14. ## Re: Designing a ported box with George

Originally Posted by LBX2G
so am i correct .
yup. slotted port

15. ## Re: Designing a ported box with George

I'm experiencing deja vu...

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