# Single Port



## greg.r26 (Mar 2, 2010)

Hi. I'm new on here so firstly hello to everyone.
Been tinkering with car audio for a while, usually toward SQ using sealed enclosures. Tried 8, 10, 12, and 15" subs but thought I would try ported for a change. At the moment I have 2 x JL 8w3v3's. 
OK, onto the question:
What is the math behind using 1 port for 2 woofers in a common enclosure? Do we double the Vas and cone area and then use the normal calculators?
Tried searching the forum and google but no real luck.
Thanks
Greg.


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## cubdenno (Nov 10, 2007)

same math as 1 woofer. Its based on volume. Since you are moving double the air, you need to figure on a larger port area to compensate for this added air in the case you are trying to avoid chuffing. I figure a couple of 3"ID ports or a 4"ID should work fine with minimal chuffing. Look up WinISD pro and try installing that on your computer. Slight learning curve but not terrible.

The other thing that a lot of SPLl guys do, is figure 12-16 square inches of port are per cubic foot of volume.


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## greg.r26 (Mar 2, 2010)

Thanks Cubdenno. I was beginning to think no-one cares 
There is a way to use the standard enclosure calculators for one woofer but by doubling a couple of the parameters (or halving some?) the results for Vbox and port dimensions are calculated for 2 woofers in the common enclosure. I found the 'trick' a few years back but have lost it.
Any more insight would be appreciated.


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## cubdenno (Nov 10, 2007)

I use WinISD Pro for my port dimensions. Plus it allows me to see air velocity in the port.

What is the volume of your enclosure?


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## greg.r26 (Mar 2, 2010)

I wanted to calculate the enclosure with the 2 w3 woofers and a single 4" port tuned to 35Hz. Going to look into WinISD now.


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