port size with 1 or 2 subs

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=133271
Printed Date: May 06, 2025 at 6:31 AM

Topic: port size with 1 or 2 subs

Posted By: thor492001
Subject: port size with 1 or 2 subs
Date Posted: January 11, 2013 at 2:25 PM

Does the port size change based on the amount of subs? Is the size (Cubic FT) the deciding factor? I realize the subs will take up some space too.

Replies:

Posted By: DYohn
Date Posted: January 12, 2013 at 10:34 AM

Both factors are in play. The size of the enclosure determines it's tuning frequency with any particular port size, but multiple drivers produce more SPL per watt than a single driver so that will determine port air velocity. You want to choose a port size that will create the tuning you require while making it large enough that the port air velocity stays low.

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Posted By: thor492001
Date Posted: January 12, 2013 at 11:02 AM

how do i calculate the larger port size. i'm building a box 25" X 15" X 15" with a 2" Slotted port to tune to 34hz. i'm able to get the length for one driver from the RE audio box designer.

Posted By: DYohn
Date Posted: January 12, 2013 at 11:45 AM

The length of the port to tune your enclosure to 34Hz will be the same no matter how many drivers you use (as long as you take into account the volume occupied by the drivers.)

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