when i first ran auto cal thought the very loud was a precaution .. they arent kidding .. the 2 bursts on the normal channels are potent .. but as you said the 3 or 4 bottom burts on the sub made me think it was ( bottoming the VC..) but once it dialed in it sounds great in actually movie .. but yes scared me at first.. thought it would blow sub .. make sure if $$ sub it has BASH technology ..