formula for highest spl

I know that their is a computer program that will assist in finding the best box type and size for subwoofers.

I saw it used a few years back and I would like to get one.  If any knows of such program I would like to know the name and how to get it.

I'm pretty sure their is an old school way of doing the same thing thing on paper.  Any thoughts on that would be nice also.   

Hey Audio Xclusive,

My personnal fave is a freeware at:

http://www.linearteam.dk/isd.html

There are two programs FREE for grabs, one is WinISD and the other is WinISD Pro.

WinISD Pro Alpha is a great program under development but already has all the features of programs costing hundreds.  For example transfer function magnitude and phase, max power, delay, SPL, excursion, vent velocity and gain, etc......with the ability to see changes in "real time". 

I'm hoping that if enough guys download this program the author will be encouraged to add the final touches.  A boost is of course to let him know what we think and the bonus is to tell him what we'd like to see.

BlauBox is another popular program but see for yourself that the two don't compare.

If you feel like ya just gotta spend then try TERMPRO developed by Wayne Harris also the brain behind DB Drag. http://www.termpro.com

Also while your there follow this link to some interesting utilities : http://www.termpro.com/programs/archive.html

Have Fun!