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Vent Size

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=14508
Printed Date: July 05, 2025 at 8:06 AM


Topic: Vent Size

Posted By: ucantbeme
Subject: Vent Size
Date Posted: June 05, 2003 at 4:12 PM

I am designing a new enclosure for my subs (2 audiobahn 1208q). The recomended air space is 3.0 cubic feet and it recomends using 2 4"x14.5" ports. Well I am wanting to design an enclosure with either one vent going straight down the middle of the 2 subs or have 2 vents on each side of the subs. I need help determinig what the vent sizes should be. I want to tune them to about 45 or 50 htz. If anyone knows where I could get any kind of info on vent or can help me out, please reply.



Replies:

Posted By: esmith69
Date Posted: June 05, 2003 at 4:39 PM
I dunno if this might help you at all?

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Ethan
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"Patience, persistence, and perspiration make an unbeatable combination for success"
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Posted By: ucantbeme
Date Posted: June 05, 2003 at 6:19 PM

yea i did thanks a lot





Posted By: bberman1
Date Posted: June 06, 2003 at 7:04 PM

Here are the calcs for your setup. Now not all the characters will post so if you want a copy give me your email address. These calcs are for 2 vents (one per chamber/sub)

SURFACE AREA OF PORT

To get the square inches of a ports surface area you multiply ¢³= 3.14 times circumference of the port. IE (4¡±)
If you have multiple ports you then multiply the results by the number of ports that you have. So if you have (2) 4¡± ports then you calculate as follows

3.14 X 4 = 12.56  12.56 X 2 = 25.133   25.133 Is the surface area of the two ports now combined

four is the size of port 12.56 is the surface area of one port the X 2 means that you have 2 ports and 25.133 is the total volume of both ports.

HOW TO CONVERT A CIRCULAR PORT TO A SQUARE PORT

If you want to use square ports, use a port whose height multiplied by its width equals the 'port area the port length will be the same as the round port.
Let¡¯s say you want to convert a 4¡± port which is 14.5 in long to a square port. Multiply 3.14 X 4 = 12.56 now calculate what times what would = 12.56 or 12.5 2 X 6.25 =12.56 so you have a port that is 2 X 6 ¨ù X 14.5 long 
Or if you have 25 sq/in of surface area and a length of 14.5  you calculate:  25 % by 2 =12.5 so you have 2 X 12.5 X 14.5 long.






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