View Full Version : Need help getting my box built.

07-12-2008, 02:02 PM
I have a 12'' Alpine type r, swr-1242d dvc sub. Alpines website suggested .75-1.75 cubic ft box for a slotted port at 33hz tuned.

They gave these external dimensions 18x13.5x16.5 and after vent and sub displacement the internal gross volume would be 1.7 cubic ft.
The vent length they give is 22.75'' with no height so I am assuming the height will be the internal height of the box. They also do not give the width of the port, or I might just not understand the part that specifies it.

My question is this, is 1.7 cubic ft tuned to 33hz gonna be perfect for this sub? I see other boxes on here tuned to 32-34 hz and they are over 2.0 cubic ft. I here a lot of people talking about slot ported boxes being bigger and better.

If anyone has any advice or a blueprint for this box or a box that will work for this sub I would greatly appreciate it.

It will be going in a 2000 VW VR6 powered by an ALPINE MRP-M500 at 2ohms 500 watts rms

07-12-2008, 04:22 PM
2-2.5cf at 32hz would be better.

07-13-2008, 02:22 AM
I figured out the box size I think. I came up with roughly (internal) 21.25x13.75x14.5 = 2.2.
I then subtracted the sub displacement .071 and got 2.1 cubic ft rounded off.

I figured out the slotted port length at 28.8'' at 33hz tuned
To get the vent displacement I did as follows- 28.8x14.5x0.75= 313cubic inches
the 28.8 is the vent length- 14.5 is the internal height and the 0.75 is the mdf thickness.
I'm not 100% positive this is how to get the vent displacement but it seemed to work.

I then added that volume 313 cubic inches to the box and got 2.4 cubic ft.
My new dimensions to keep the box tuned to 33hz after the vent displacement are as follows, internal measurments 22.5x12.5x14.5 = 2.39 cubic ft rounded up.

Is this correct? I Friggin hope it is. I never did this much math in my life. Someone, anyone please shed some lite on this subject.

Thank You

07-13-2008, 02:04 PM
Umm you'll want you port to be wider than .75"

And you will also want to take into account the port wall.

07-13-2008, 06:29 PM
That .75 is the thickness of the mdf not the port. The port will be 2'' x 28.8''. The measurement of 28.8 x .75 x 14.5 is the vent wall that will be in the shape of an L.

07-13-2008, 10:18 PM
Ok, sounds like you got it down..

07-14-2008, 12:14 AM
Hey I stumbled upon this website during my internet journey.
Reaudio.com I used the calculator on the site and got different numbers but not by much. Just wondering if anyone has used this and if it worked out good for them?

07-14-2008, 12:26 AM
I use carstereo.com