concentrate on ur shooting la... still playing carhifi meh?that medium pass must be full range la, or flat, or filter off, etc etc etc
anyway, MBQ is cap ayam, what do u expect for RM350
the original one is called MB Quart, and their amps would be around 2k-3k
keep it at lowpass, bcoz the sub is only supposed to play low frequencies (bass, sub bass). the rest of the frequency range (midrange and treble as u call it) should be played by your other speakers (midrange and tweeter)
anyway, my guess is the amp isnt powerful enough....