I know the designer of this woofer. FEA was used extensively in its development. He(the designer)did say he preferred the sound of the swr series of drivers from alpine.
I own 4 SWR-1542d(21.4mm xmax) and have them in 3 cubic foot sealed cabs, driving them with a pair of ep4000. They are an earthquake machine....however overtime I have grown to find them to have a heavy sound.