Hello,

I am new to this forum and the proud owner of a new dual 2 ohm Q12 with BP option. I am looking to build a ported box for the sub tuned to the recommened 32hz. I would appreciate some help with the design. The sub will be powered by a Soundstream PCA1500D. I will most likely run the sub at 4 ohms for a while until I upgrade my Big 3 sometime this summer.

I would like the box to be a slot port with rounded corners somewhere in the range of ~2 cubic feet. The box will be made out of 3/4" mdf

Box outer size (max):

12.5" tall

30" or 32" wide (can't recall the correct measurement right now)

Depth is variable

So far my calculations have brought me to the following:

2.0 cubic feet

slot port 11" x 3" internal

33.18 inches long

Does this look correct? I am open to suggestions on any changes, etc. Should I make the internal volume large with a shorter port? More or less port surface area?

Thanks in advance for the help.

For 33sq inches your port is too short to hit 32hz. How did you come up with 33" long?

I used the following website for the calculations:

slot port calculator

I appreciate your help.

Box Parts (Square Prism)

1 Top, 1 Bottom: 13.5 x 30 in

0.75 (thick) in

1 Front, 1 Back: 11 x 28.5 in

0.75 (thick) in

2 Sides: 11 x 13.5 in

port :

6 x 3x 21.5 long

Box Properties:

Type: Vented Box

Shape: Prism, square

Vb = 1.934 cu.ft

Fb = 32 Hz

Fill = minimal

No. of Vents = 1

Vent shape = rectangle

Vent ends = one flush

Hv = 6 in

Wv = 3 in

Lv = 21.5 in

Box Parts (Square Prism)

1 Top, 1 Bottom: 13.5 x 30 in

0.75 (thick) in

1 Front, 1 Back: 11 x 28.5 in

0.75 (thick) in

2 Sides: 11 x 13.5 in

port :

6 x 3x 21.5 long

Box Properties:

Type: Vented Box

Shape: Prism, square

Vb = 1.934 cu.ft

Fb = 32 Hz

Fill = minimal

No. of Vents = 1

Vent shape = rectangle

Vent ends = one flush

Hv = 6 in

Wv = 3 in

Lv = 21.5 in

You need way more port area than that!

I don't trust those online calculators, I'd prefer to do it by hand.

Box Parts (Square Prism)

1 Top, 1 Bottom: 13.5 x 30 in

0.75 (thick) in

1 Front, 1 Back: 11 x 28.5 in

0.75 (thick) in

2 Sides: 11 x 13.5 in

port :

6 x 3x 21.5 long

Box Properties:

Type: Vented Box

Shape: Prism, square

Vb = 1.934 cu.ft

Fb = 32 Hz

Fill = minimal

No. of Vents = 1

Vent shape = rectangle

Vent ends = one flush

Hv = 6 in

Wv = 3 in

Lv = 21.5 in

You need way more port area than that!

I don't trust those online calculators, I'd prefer to do it by hand.

I don't trust them either, so I use my spreadsheet to verify.

i did it in BassBoxPro6

i addmitt i dont like designing / not knowing what sub or the T/S specs...

just trying to help, i use it for my designs anf it usually bangonn

Edited May 31, 200718 yr by Lord Baccus

Do you think that 18" vent area will be enough? It seems as though Fi recommends 12 to 16 inches per cubic foot of box. That is why I was using such a big vent area.

Does anyone know if the equation from the following website is any good/accurate?

http://mobile.jlaudio.com/support_pages.php?page_id=165

Was the port of the above enclosure a slot port or a normal rectangular port? I would really like to find a way that I can reproduce the same results as the box from above so that I can play around with the enclosure specs myself.

Wow, there was 3 updates while I was typing my response ... Could you point me to where you got the equations you used in your verification spreadsheet?

Edited May 31, 200718 yr by cheqmate

i just copied the specs from BBP6 & pasted em on the reply...

if you have the link to the T/S i can get you a plot...

& i dont recomend using a box designed for a JL sub when your using DD, your foot wont fitt my boot,,, i recomend designing a bof just for the DD ...

problem is the boxx is so small you cant go too bigg with the port...

So I now have BBP 6 installed and I have started to play with it. I am getting slightly different numbers than Lord Baccus did, but they might be rounding errors.

The t/s parameters for my sub are in the link below:

t/s params

Approximately what length would you expect for a port area of between 24 - 32 sq. inches.

Does anyone know how to calculate vent air speed? I want to make sure that the port area is large enough to not have port noise.

I will be designing tonight and post what I find.

Thanks for the help so far.