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View Full Version : Finding a drivers Vb.



mackin13
03-04-2007, 09:34 PM
Turns out this involves more thinking than im used to. I dont have any trouble building a physically sound box, its just i cant seem to design one worth ****.

Im trying to find out what volume i should use for my massive cw12. At first i thought i knew what i wanted and i built a box for 2 ft^3 tuned to 32. Box needs to be bigger, isnt hitting real low, but i have no idea as to how big. I tried using this formula:

Vb = Qts 2.87 x 15 x Vas

According to my drivers specs, my box should be 4.373 ft^3. This sounds a little big for a not so big speaker, or am i wrong? Other people on this forum run their cw12's in around 2.5 ft^3 but i am clueless as to how they determined this other wise arbitrary calculation. Some one please help. I have no trouble calculating anything else, and im so close to finishing this build, just need to re-cut my side pieces according to my boxes VB. Thanks

Fs: 33
QTS: .642
VAS: 27.12 (liter?) or 1.04 (ft^3?)
QL: ???
QES: 0.733
xmax: 20.5

And, any one know how to use those stupid free ware box designers? I cant seem to get windows to run mine.

Thieroff
03-04-2007, 09:35 PM
I can design a box for you, if you'd like


CT

ngsm13
03-04-2007, 09:59 PM
See the sticky at the top of this forum.

For that driver, I would do around 2.5 cubes tuned to 33hz.

nG

mackin13
03-04-2007, 10:05 PM
Phew, thanks.

My currents box has 4.8 ft^3 before you figure in port displacement. I will be using a slotted port wich will be using the walls of the box. My two known port dimensions are 17.75 in x (optimal width?) x (unknown). My port length cant be any longer than 36 inches (so i dunno how that affects tuning). I would like for this box to be tuned around 33, but i dont know if i can get a port long enough for that to happen.

This is a custom box similar to that one that guy threw in his camaro, except the angles arent as sharp. Here are some pics for what my box should look like. I have most pieces already cut and angles done, so if the box needs to be smaller im just going to reduce its width (17.75 in).

http://www.tundrasolutions.com/forums/attachments/classifieds/16047d1167783402-sale-audi-xxx-12-subwoofer-custom-re-sub-4.jpg

http://www.tundrasolutions.com/forums/attachments/classifieds/16044d1167783402-sale-audi-xxx-12-subwoofer-custom-re-sub-2.jpg

mackin13
03-04-2007, 10:55 PM
I have the outline of that box done. The side measures 478.91 inches squared. My orignal width was 17.75 inches, wich would give me a net volume of 4.97 ft^3. (My driver displacement is .095 ft^3)

I am having trouble guesstimating the width of the box as i have no idea how much area the port is going to subtract from the net volume... Wich is why i find this whole thing very confusing and inexact. Not a big fan of guesswork. Sorry, this is only my 3rd box.

16 inches wide.
Vb: 3.5 cubes

mackin13
03-05-2007, 05:09 PM
Nevermind, finally figured out how to narrow it down. Came down with somthing reasonable given my strange box shape.

3.07 ft^3
Should be around 32 hz.
Port dimensions are 3x16x34.75