twas actually mad easy pimpin
regular ported box calcs for the chamber holding the driver half that for the smaller chamber....determine the response you want and base the tuning of the chamber holding the driver off of that and then the empty chamber tuning should be 15% less then that of the larger chamber....so experimentation will incur to get it just right for each woofer tho..took me three tries of sizes and tunings to get the assassin right..in the end it was 1.85ft tuned to 31 and .925Ft tuned to 26