Ok. ive got 3 JL Audio 12w3's in a truck box. they are running off a Lanzar Vibe 1200D mono amplifier. ive got it wired so that the amp recieves a 1.5 ohm load. the outside 2 subs are wired in series, and the middle one is in parallel. i have 4 ga. power wire and 12 ga. speaker wire. the wires are spliced as soon as they enter the box. when i have a song w/ lots of bass in, and turn it up, the middle sub makes a horrible noise. i dont think it is bottoming out, but maybe overextending. what could be causing this, and what can i do to fix it?