Hello as a front system have the phase Linear 165.25 Fully active on a Helix 400 MK2 with the matching crosscards, as headunit I have the Alpine 9855 R. tweeter sits in self-built mirror triangles Now my problem of high sound is too intrusive not from the level but simply from the music. I find it dissolves too far still (frequency band). Does anyone know where I get a low pass filter from about 18kHz or, if I can build it myself ???? And then which values for Wi state and capacitor?? Thank you already in advance