View Full Version : 1 or 2 port sub box

07-12-2009, 10:49 AM
:wow:Hi all, Im building a ported sub box and im trying to use a port length calculator found on the web(http://www.carstereo.com/help/Articles.cfm?id=31). I need help understanding the results for 1 port vs 2 ports. The box volume is 2.5 cubis feet, the tuning freq is 25hz, and im using a 3" port. Now with 1 port I get 10" length and with 2 ports I get 22.19". I know increasing the ports reduces the resistance of air flow but do I have to divide the 2 port number by 2 to get each port length or is that for each port. No, Im not new at this but Im really having a hard time with this and any advise would be great. Thanks

07-12-2009, 10:55 AM
if you use 2 ports, both ports will be much longer than one port will be. i would suggest you use one larger round port or a slot port.
one 3" port will have a lot of port noise and haveing 2-3" ports may as well.

areo ports work wonders as well with port noise.

07-12-2009, 11:10 AM
Thanks, I do know about port noise and slot ports. I do have a Precision Port 3" Flared Port Tube that works great and because of the design of my box a slot port is not practical. The other problem is going with a bigger single port increases the length and will cause problems.

07-12-2009, 11:12 AM
what kind of sub is this for? thats a really low tuning

07-12-2009, 11:35 AM
Its for a JL 13" W3V3 2ohm sub. I got the numbers off the web site. Did I get the wrong numbers? Thanks