Can anyone tell me what might cause a distorted sound / Speakers working backwards. My set up is Ampeg SVT 3 Pro with two Markbass 104 HF / 4 Ohm cabinets. I'm playing Epiphone T-bird pro. Problem occur when I hit low notes on E string. Time to time coils pull back hard. Signal is clear when I use my back up amp (EBS 250W head).