splw 152x subwoofer box

I have a friend who needs a box built for 4 of these Spl Gorilla subs. The spec sheet calls for 4 ft of air per sub (which we have) The problem is this is going to be an open chambered enclosure and the spec sheet only gives round port size. Could someone please tell me what size slot port this enclosure would need to get tuned to between 35 and 40 hz? The box is 48" w x 37.25" l x 20" h  and the round port size for 1 sub is (2) 4" x11.75" I do not know how to convert the port from round to square. The website for spl is www.splusa.net and the subs are the SPLW-152x. Your help is greatly appreciated.

go to the calculators page on the12volt.com and enter your specs.  itll tell you what you need to do.    i use this calculator for all of my enclosures and its pretty accurate.   good luck. i hope it works out for you.

splsled wrote: I have a friend who needs a box built for 4 of these Spl Gorilla subs. The spec sheet calls for 4 ft of air per sub (which we have) The problem is this is going to be an open chambered enclosure and the spec sheet only gives round port size. Could someone please tell me what size slot port this enclosure would need to get tuned to between 35 and 40 hz? The box is 48" w x 37.25" l x 20" h  and the round port size for 1 sub is (2) 4" x11.75" I do not know how to convert the port from round to square. The website for spl is www.splusa.net and the subs are the SPLW-152x. Your help is greatly appreciated.

They are using 25 sq.in. of port for 4 cubic foot, per sub. So a slot port say 10"x2.5" would be the same as the 2 4" round ports. 4" round port. R2 x Pi= area. So 2 x 2 x 3.14= 12.56sq.in you have 2 needed for that airspace so 12.56 x 2= 25.16sq.in of port area. Using the calculators on this site will help you to find the length you need for you selected tune, however you need to use net volume for them to be correct. Net is minus port volume, driver displacement and any additional bracing. That will occupy the gross internal airspace.

Thanks alot for the help, I have it figured now and after reading the paper that came with the subs it called for 4 ft of air per sub, the driver displacement and port is figured into the 4 ft so it makes it a little easier. Great site!!