Math check on sa 12 box

[lilrezy50]

I am wondering if someone would be willing to check my math on this enclosure for 2 sa 12's

14.25" h

30.25w

12" depth 1

15" depth 2

(wedge enclosure)

3/4" material 

= 2.55 ^3ft internal air space

Sa's will displace .28^3 leaving 2.77^3

To achieve 35hz tuning, aero port will be 4" diameter by 9.25" long

port displacement V = radius x pi x length = 4^3 x pi = 50.26 x 9.25 = 464.9 ( 465 cubic inches) - converted to .269 cubic feet rounded to .27

so remaining displacement of 2.77 will end up being 2.0^3 after port displacement 

[Jessica]

1 4" aero is not enough. try 3

[Jessica]

i ran 4 sa'12's in 9cuft with 126" of port area. it was pretty nasty. 

[lilrezy50]

I might consider that, but how does that math look

[Triticum Agricolam]

I get 2.21 cu ft net after sub and port displacements.  

That's too small for a pair of SA-12s and like strangeduck said, no where near enough port area.  

Here is a port area calculator to help you get a better idea how much port area you should have: https://goo.gl/STAv4p

[lilrezy50]

What I am thinking is a new design that is 4.243 net volume

3.96 cubes after woofers

I need at least an 8" port for 50 cubic inches roughly as my minimum port area is 47 with 1600watts, and tuned to 35

My question is, if I have 3.96 cubes to work with, an 8 inch port internally will take up 22 inches and displace too much 

can I mount two 4 inch aeros internally to make that 8" area up? they will only be roughly 4 inches long and take .11 cubes of displacement each leaving 1.87 cubes per woofer

or I can mount the 4 inches externally to leave 1.98 per woofer

[Jessica]

Two 4" ports is not the same as 8". I'm going to ask you to find the area of a circle. Once you know how to do that you can figure out to achieve your port area

[lilrezy50]

Area = pi * r^2 so 

8" port = 

16 sq in  * pi = 50.26 sq in

[lilrezy50]

I see as well, 

4" port = 4 sq inh * pi = 12.56 x2 = 25.12 sq in for both ports where as 50.26 for the single 8 inch 

[lilrezy50]

Here is where I think I land best

Height 14.25
Width 30.25
Depth1 22
Depth2 25

4.66 cubic feet = 4.38 after sub displacement (.28)

Port Diameter (D) 8    Box Volume (Vb) 4.38    Tuning Frequency (Fb) 35hz         Port Length   19.4

Pi(r)^2(height)/1728

3.14 * 16x19.4 = .56 displacement

4.38 - .56 = 3.82 = 1.91 per woofer

 

How does that look?