1. ## Simple Ported Box Question:

Hey guys (and girls) I'm new here and I've looked for my answer by searching, etc. but there is so much information within all of the forums, I can't find exactly what I'm looking for. I was really into car audio a few years back, but until recently, I've been chasing the speed bug.

My question is: When you're building a box, do you count the port area as internal volume? Which of these boxes are correct? Thanks in advance!

Target internal volume: 2.43 Cubic Feet
Speaker Displacement: 0.48 Cubic Feet
Port Displacement (19" x 5"): 0.215 Cubic Feet

2.43 + .48 = 2.73 Cubic Feet

-or-

2.43 + .48 + .215 = 2.945 Cubic Feet

2. ## Re: Simple Ported Box Question:

it goes like this

target internal volume: 3.5 cubes
speaker displacement: .18 cubes
port displacement: 1 cube

so if your aimin for 3.5 cubes you need to build a box that is 3.68 cubes internally so that when the sub is placed in, it will get its 3.5 cubes. now add the port displacnement and that gives you yoru gross volume which is the whole box while net volume is wha the sub sees. let me know if i confused you

3. ## Re: Simple Ported Box Question:

Originally Posted by George
it goes like this

target internal volume: 3.5 cubes
speaker displacement: .18 cubes
port displacement: 1 cube

so if your aimin for 3.5 cubes you need to build a box that is 3.68 cubes internally so that when the sub is placed in, it will get its 3.5 cubes. now add the port displacnement and that gives you yoru gross volume which is the whole box while net volume is wha the sub sees. let me know if i confused you
So, you don't conpensate for port volume, correct? In you example, the box would need to have 3.68 cubic feet of air space (empty) and not 4.68 cubic feet?

4. ## Re: Simple Ported Box Question:

ok, the port does NOT count for the subs 'wanted' volume.

so if i wanted a RE SE 10" subwoofer (i have one ) and RE says "it likes 1.2cubes ported".

it needs 1.2 cubic feet behind it. the sub displaces lets say .2cubes (for ease). now i need my box to compensate for the area that the sub takes up, so it now needs to be 1.4 cubes. so now i have my box size. 1.4 cubes (after sub displacement)... so i go to the port calculation and i say, lets do 1.75 wide, but 11 tall, gotta be about 34" long (made up). that is gonna take up .37 cubes not including the wall of the port (lets say .75" thick, 3\4 MDF) and there is no bend in the port...that piece of wood takes .16cubes itself. so the gross port volume (inside the box) will be .53... so we need to make a box that is 1.4+.53. that would be 1.93 cubes for the entire box... and thats internal.

port does NOT include inner volume. the inner volume must be what is recommended for the sub, and the port should be added to this for the GROSS volume. everything that goes into the box must be taken into account so it stays at the required volume.

5. ## Re: Simple Ported Box Question:

Originally Posted by req
ok, the port does NOT count for the subs 'wanted' volume.

so if i wanted a RE SE 10" subwoofer (i have one ) and RE says "it likes 1.2cubes ported".

it needs 1.2 cubic feet behind it. the sub displaces lets say .2cubes (for ease). now i need my box to compensate for the area that the sub takes up, so it now needs to be 1.4 cubes. so now i have my box size. 1.4 cubes (after sub displacement)... so i go to the port calculation and i say, lets do 1.75 wide, but 11 tall, gotta be about 34" long (made up). that is gonna take up .37 cubes not including the wall of the port (lets say .75" thick, 3\4 MDF) and there is no bend in the port...that piece of wood takes .16cubes itself. so the gross port volume (inside the box) will be .53... so we need to make a box that is 1.4+.53. that would be 1.93 cubes for the entire box... and thats internal.

port does NOT include inner volume. the inner volume must be what is recommended for the sub, and the port should be added to this for the GROSS volume. everything that goes into the box must be taken into account so it stays at the required volume.
Great information, and it answered my question exactly... Thanks!

no problem.

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