I got a sub enclosure from a friend that works at best buy, its a band[pass box. It came with a chart where you use some stats from the speaker to tune the port length, but it says that the ports should be 37 inches for my alpine type r.

There are 4 ports total on the box and 2 enclosures for 2 subs, the chart doesnt really specify wheter each port should be 37 inches each sub should have 37 inches of port or if its a total for all four. Right now each port is only about 6 inches, how could I lengthen it?

By the way, polyfill is supposed to make the box seem bigger would that help? and where would I get some from?

Thanks for any help