What size port would I need?

Question

I have a box that is 18 high x 16.5 wide x 20 deep (Internal measurements of 16.5 high x 15 wide x 20 deep). I was wondering what size I should make the port. I was going to make the port like an actual seperate little box inside the speaker box but it would be alot easier if I just used the inner wall of the sub box. But now I am not sure how wide I should make the opening if I do use the inner wall of the box. In the manual I have for the sub it said to make it 3high 11.5 wide x 22.5 deep. I called kicker and they said to tune it to 41hz. That seems a little high doesn't it? (I have a kicker cvx 12"). How would I know how big to make the port and how deep to make the board?

Link on the sub I own:

http://www.kicker.com/06/tech-support/manuals/manuals/2006/2006%20CVX%20Sub%20a01%20WEB.pdf

Answer 1

a general rule of thumb is to use 12-16sq" of port area (its opening) per every cu' of the enclosure. and yes 41 is pretty high. for this we will not use kickers diemesions at all.

the formula for find port length is as follows...

Lv = [(1.463 x 10^7 x R^2)/(Fb^2 x Vb)] - 1.463 x R

Lv = length

Fb = tuning freq.

Vb = int. vol in cu"

R = radius of port (for slot/square port: R = sq.rt. A/Pi)

so....if we make you port 16.5H x 2.5W thats gives us 41.25sq" of port area....and tune to 32Hz...

Lv = [(14630000 x 13.14) / (1024 x 4950)] - 1.463 x 3.62

Lv = (192238200 / 5068800) - 5.30

Lv = 37.93 - 5.30

Lv = 32.63

32.5 will get your 2.8cu' box tuned to 32Hz using 41.25sq" of port....now, if your box is already built, by adding this port into it, your making your box smaller so you would need to account for the port displacement. the volume of the port, if you using 3/4" mdf, will be 31.75 x 3.25 x 16.5 (the 31.75 comes from subtracting the front face of the box and the 3.25 comes from adding the side 3/4" side wall of the port)  = 1702 cu"....subtract this form your original box volume and do the calculation over again. in this case you get a port that is 52.5" long. being this is pretty long, you may want to have a higher tuning freq. or less area. the main thing to remember is the smaller the box, the longer the port needs to be to tune low...the more area the port has, also the longer it needs to be to tune low.

i gave you the formula with a really good example. play around with it to have it work for you. i wouldn't go over 38Hz for tuning and no less than 12sq" of port per cu' of box (in your case about 35sq")

one last note: if you use the side of the box as a wall to you port (usually this is the case) you need to add 1/2 of the port's width to it length. add this after all calculations are done. this is only done when a port shares a wall with the box. (this is called the port correction factor)

if you have any Q's...hit me up.

Answer 2

idk how wide to make it so i'm not going to lie but make it as long "deep" as possible it will tune it lower and lower the longer it is did kicker say you should port it?? cause not all subs need to be ported some subs sound bad in ported boxes and others sound beter in them if kicker said to do it then ask them the width to make it  that would be the most reliable source you can find i hope i helped even a lil