i going to build a ported box and was wondering if there is a ratio of box lenght to port tube length or something like that. any help is much appreciated.

 

what sub do you have? look on their website and they should have recommendations for the specs and port size

 

thanks
can belive i didnt think of that

 

If you're looking to build a box, first find out the maximum external dimensions that you want to use. then, find out the recommended airspace and tuning for your sub. this information should be on the sub manufacturers website. if not, call them. then, use calculators here:
http://www.the12volt.com/caraudio/boxcalcs.asp#porsq
to help you figure out the length/width of your port. then it's just time to cut and build...

 

I'd download WinISD. Should have lots of subs preloaded, or able to add your sub based on ts specs. Should be able to calculate out a box easily if you know a net airspace volume.

might take a little knowledge to understand frequency graphs and design a box you like, but I think it's worthwhile to learn.