I am trying to use WinISD (its free, eh) to design a bandpass box for a couple IDQ10 D2 V.2 subs. I have all the required parameters except Le and BL (Qts, Vas, Fs, Re, Xmax, Z, Qms, Qes, SPL, Pe, dia, Sd). Do these make any difference whatsoever in the design of the box, can I calculate them from the other parameters? BL - The magnetic strength of the motor structure. Le - Length of wire immersed in magnetic field, in meters. Doesn't look like it to me.