SDC ported box

[suprefly 0]

Hey I want to build a ported box for 2 12" SDC2.5s, but I've never built a ported box....and it confuses me

On the Audioque site it says each sub should have 2.5 cuft and that includes the port and sub. But what should the port length, width etc be?

I've searched and read up on a lot of stuff and other peoples' builds, but still am not sure what do.

[Kanaworm$ 292]

Dimensions of box?

Audioque recommends a tuning of 40hz or so.

Also check out there "System Design" tab and it lists all the info you need.

[suprefly 0]

A 31.75 width x 19.75 depth x 13.75 height (inside dimensions) gives me 4.99 cuft.... so i'd need 79.84 sq inches of port? And then the port width would be 5.81 in and 13.75 in tall...and then make it 16 inches long right?

Edited March 27, 2009 by FF5

[suprefly 0]

OK scratch the above....tell me if these are good measurements. The subs are going on the vertical face, not the slanted one.

Ideally these are my outside measures:

depth bottom=24.75, depth top=20.25 width=30.5, height=15.5

Inside:

db=23.25, dt=19.5, w=29, h=14

I got 5.022cuft..........port measurements (for the inside right?):

L=16, W=5.75, H=14 Area=80.352sq in. tuned to 40hz (i assume its 40hz from Audioq's website)

I used http://www.mobileinformationlabs.com/HowTo...0Volum_1%20.htm to check myself...

Please tell me if these are all the right numbers for 2 12" SDC2.5s! Thanks

Edited March 28, 2009 by FF5

[Joker 0]

depth bottom=24.75, depth top=20.25 width=30.5, height=15.5

I get 4.93cuft using 3/4" MDF with the above measurements . That does not include the driver displacement or the port displacement .

You need a bigger box , whats your maximum space height / width / depth ?

[suprefly 0]

Hmmmm....you're right.....let's see. Everything is inside dimensions.

The area should be .5(base1 + base2)wh=.5(19.5 + 23.25)(29)(14)=8678.25in^3=5.022cuft

If i want 4 cuft and a port tuned to 38Hz (DJ said is would sound better for daily) then my port dimensions if i put the port horizontal across the bottom are L=20 w=29 h=2.25 Now the volume of the port plus the thickness of the wood is (20)(29)(3)=1740in^3=1.01cuft

The subs, according to DJ=0.1cuft

4.582+.441=5.023cuft and -1.21cuft for displacement so 5.022-1.21=3.81cuft

So I'm still off, which I figured out right after i cut the top, and i'm going to fix it by using "steps" on the top" (see my build log). Kinda sloppy, but I'll probably just end up building another better box this summer.

[Joker 0]

Yeah you may have some problems with that box . First thing I see is the port area is alot for the final displaced volume .

Your internal port of 2.25" H x 29" W = 65.25sq in

65.25sq in divided by 3.81cuft = 17sq in per cuft (over the rule of thumb 12-16sq in per cuft most builds are based off of )

Another problem I see is the height of your port is small for how long it is giving it close to 9:1 length/width (in your case height) ratio.

The rule of thumb most go by is keep it under 9:1 , some like under 8:1 .

Just stating my observation by the information provided , your box may have some port noise is all .

If you reduced the port area you would gain internal volume .

[suprefly 0]

Didn't know about the 9:1 8:1 ratios, thanks! I'll keep that in mind for next time