View Full Version : Port size & Lenght

12-26-2006, 03:58 PM
I've done ready and tried the port calculators and am a little confused. I notice when a box is bought there are normally two ports per sub and at least 3 to 4 in in wide. The leghnth is normally less that 6 inches long. But when I use the calculator to figure out what i need and it is not in the norm of what ive seen.

I have a box that is 1.4824 cf I want a 3" port and it comes out to 8.29551 in leghnth. If I use a 2" port it goes to a 3.19923". & I thought it was the other way. The bigger the port the shorter, guess not.

Also if I go with 2 ports the ports get longer. There again I thought it would get smaller. Is this right or am I just missed up.?

Just through this out there cus my whole thought of ports is wrong. Can someone simplify the reason byhind this.

Thanks in advance


12-26-2006, 03:59 PM
prefab is junk :fyi:

12-26-2006, 05:44 PM
The length will increase as the volume of the port displacement increases. This is why you see the jump fro 2" to 3" dia and when adding ports you should see the length almost double for every one added.

It looks like your trying to tune to somewhere around 36Hz with the numbers your giving, but you need to remember to compensate for the port displacement when you do you math. If you do not tuning will be higher as tuning will increases as your box volume decreases.

12-26-2006, 08:01 PM
Thanks, that does help. I will make the adjustment and let u all know what happens. & yes I was aiming for 35Hz:)

12-28-2006, 10:02 AM
Hey, if I want to go with a slot port what would my specs be for that. I am not sure bout the length


12-28-2006, 10:54 AM
What are you max dimensions?

12-28-2006, 12:49 PM
I did not want to go over 26" wide and 15 High and depth about 14"

I did not want to go to big. its for a single 12" Alpine SWR-1242D

Thanks in advance:)