Box Design Help

[cheqmate 0]

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.

[///M5 2,833]

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

[cheqmate 0]

I used the following website for the calculations:

slot port calculator

I appreciate your help.

[Lord Baccus 1]

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

[///M5 2,833]

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.

[ANeonRider 3]

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.

[Lord Baccus 1]

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, 2007 by Lord Baccus

[cheqmate 0]

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, 2007 by cheqmate

[Lord Baccus 1]

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...

[cheqmate 0]

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.