ive re grounded both subs, both work perfect when on, and if i put one of them on (right one) then works fine, but if both are on,they still make that "engine noise" type sound i wiggle about cables (eg grounding cable) in the amp, and it works ok, so im guessing its the amp, but you think this can either be repaired, since its prob a loose socket? or covered under warrenty, since its not my fault?