Port Length

Ok. I need to know how long to make my ports. The calculator on the site is only for 1 port. I want 2 for the lower port velocity. I went to www.caraudio.com or www.carstereo.com and they have a calculator for 2 ports. That site said to make them 14.51 for each. I emailed Audiobahn and they finally wrote me back and said to make them both 22 inches. Here's the details. The box has 3 chambers for 3 12's, Audiobahn AW1208T's. There is 2.69 cubic feet in each chamber. There are 2 ports in each chamber on the top at the back. The speakers are mounted backwards on the front of the box so they don't take up any air space. I want each chamber tuned to 38Hz. The port diameter is 4 inches. If any can tell me which number is right I'd really appreciate it. I hope it's the 14.51 because I cut and mounted the ports today before I got the Audiobahn email. Peace

That is wrong.  Port math does not work like that.  You cannot simply cut the length in half as it will not function the same as one longer port.  For example, to tune a 3 cuft enclosure to 30Hz, a single 3" diameter port neds to be 4.86" long.  Using two 3" diameter ports, each needs to be 11.92" long.  Here's a good calculator.