seth350

11-26-2005, 07:27 PM

I've seen a lot of people having troubles with their calculations and asking how to calculate this and that. So I just thought I would post up my method for calculating everything and it has worked so far and is quite simple to do.

Calculating cubic foot

This only works for standard boxes, not wedge boxes or circular ones.

Ok, you got a sub and now you want to make a box for it. Then you decide if you want the box ported or sealed. Lets do both. :crazy:

Sealed Box

Lets say the sub needs 2.0cuft sealed.

What you would do now is measure the maximum amount of space in your trunk or where ever your putting the box. Measure Length, Width, and Height because you will need those 3 measurments for the box.

Lets say your maximum measurements are......45"x24"x20"

You now take those measurements and get the cuft for that amount of space.

You do that by taking each measurement and subtracting 1.5 from each one and then multiply them all together and then divide by 1728.

So it should look like this:

43.5x22.5x18.5=18106.875 then divide 18106.875/1728 = 10.49cuft

Ok naturally 10.49cuft is too much. So now you mess with your measurments until you get 2.0cuft.

Ok, 20"x16"x14.4" = 2.0cuft, but since I dont like working with uneven numbers, Im just going to go ahead and make 14.4 = 14.5. Which now makes the box 2.02cuft.

Now you have your measurments that you need to cut. But remember when you cut to compensate for the thickness of the MDF which .75

Like for instance on my box I built I forgot to compensate for it and I ended up have to trim the front and back down.

All you do is subtract 1.5" from your measurment and then the piece should fit down in between the sides.

Now, you have that....now take your subs displacment and add it to your cuft of your box. So its, 2.02cuft+0.08cuft = 2.1cuft. Now thats how big your box must be in order for your box to have 2.02cuft after the sub is put in. So once again you adjust your measurments accordingly.

So now your measurments become, 20"x16"x15" = 2.1cuft

Now your sub can go in the box and have 2.02cuft.

Now you have your measurments that you need to cut.(20"x16"x15") But remember when you cut to compensate for the thickness of the MDF which .75

Like for instance on my box I built I forgot to compensate for it and I ended up have to trim the front and back down.

All you do is subtract 1.5" from your measurment and then the piece should fit down in between the sides.

Hope this helped yall. My guide to designing ported boxes can be found here...

http://forums.caraudio.com/vb/showthread.php?t=128158

Calculating cubic foot

This only works for standard boxes, not wedge boxes or circular ones.

Ok, you got a sub and now you want to make a box for it. Then you decide if you want the box ported or sealed. Lets do both. :crazy:

Sealed Box

Lets say the sub needs 2.0cuft sealed.

What you would do now is measure the maximum amount of space in your trunk or where ever your putting the box. Measure Length, Width, and Height because you will need those 3 measurments for the box.

Lets say your maximum measurements are......45"x24"x20"

You now take those measurements and get the cuft for that amount of space.

You do that by taking each measurement and subtracting 1.5 from each one and then multiply them all together and then divide by 1728.

So it should look like this:

43.5x22.5x18.5=18106.875 then divide 18106.875/1728 = 10.49cuft

Ok naturally 10.49cuft is too much. So now you mess with your measurments until you get 2.0cuft.

Ok, 20"x16"x14.4" = 2.0cuft, but since I dont like working with uneven numbers, Im just going to go ahead and make 14.4 = 14.5. Which now makes the box 2.02cuft.

Now you have your measurments that you need to cut. But remember when you cut to compensate for the thickness of the MDF which .75

Like for instance on my box I built I forgot to compensate for it and I ended up have to trim the front and back down.

All you do is subtract 1.5" from your measurment and then the piece should fit down in between the sides.

Now, you have that....now take your subs displacment and add it to your cuft of your box. So its, 2.02cuft+0.08cuft = 2.1cuft. Now thats how big your box must be in order for your box to have 2.02cuft after the sub is put in. So once again you adjust your measurments accordingly.

So now your measurments become, 20"x16"x15" = 2.1cuft

Now your sub can go in the box and have 2.02cuft.

Now you have your measurments that you need to cut.(20"x16"x15") But remember when you cut to compensate for the thickness of the MDF which .75

Like for instance on my box I built I forgot to compensate for it and I ended up have to trim the front and back down.

All you do is subtract 1.5" from your measurment and then the piece should fit down in between the sides.

Hope this helped yall. My guide to designing ported boxes can be found here...

http://forums.caraudio.com/vb/showthread.php?t=128158