View Full Version : round port to slot port conversion

04-14-2010, 12:35 AM
I am trying to design a ported box for my subs but I'm having some trouble. The manufacturer requires a 4" x 14" round port. When converting from round to slot port, do I only need to worry about surface areas of the port? So each 4"w port would have 12.57^3 in of surface area, so I would need 25.14^3 of port area for 2 woofers in 1 chamber? Then the length would determine the tuning freq?

04-14-2010, 04:29 PM
The box's net size determines the port, you need a certain port area for the given box dimensions, you figure it like this
Net box x 16 = port area necessary for max output (or close to it). This is the formula Digital Designs uses and it works very well for most applications. I never really had great luck going by the manufacturers recommendations, they tend to leave a little on the table most of the time...

So basically for a 2.0 ^3 chamber after displacements of woofer and port, you need about 32 SQ" of port opening to be in the upper efficiency range of that particular box.

pawn man
04-14-2010, 05:24 PM
pi times the radius squared

04-14-2010, 06:22 PM
Could anyone answer the question better? And are there any differences in port/sub placement on the enclosure? (rear subs and port vs. up subs rear port or up port rear subs)

04-14-2010, 06:29 PM
The location of the ports is pretty car specific. In a trunk car (which I think yours is) unless you wall off the trunk behind the seat completely usually the best placement is sub forward port back, but sometimes sub forward port forward will work better, you kind of need to play around with your particular car unless someone here has done that specific car....

04-14-2010, 06:48 PM
trunk car, sub back port back. Lol.

Also when you say a "round" port do you mean a Aero port? If so then you dont need as much port area compared to a slot port

04-14-2010, 11:04 PM
The owners manual only says 4"x14" but nothing about an aero port. I would like to go with a slot port, but just needed clarification on conversion of the given dimensions for a round port to a slot setup.

04-15-2010, 12:28 AM
Not to hijack but I have a very similar question. I'm getting two subs and the factory specs recommend 20-30 inches of port, what does this mean??

04-16-2010, 10:42 AM
That's the "area" of the port opening....if you had a port that was 4"x5" then you would have 20" of port area....

04-17-2010, 12:26 AM
use the calculator on the 12volt. just remember to use 14 - 16^in of port per cubic foot of air space(so 14 X net cubic feet). multiply height times width of the slot port opening to get square inches. input your width and height and net box volume and desired tuning freq and it will give you the required port length.

Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators (http://www.the12volt.com/caraudio/boxcalcs.asp)