I try to install my Alpine PDX1.600 amp today for my Image Dynamics IDQ12 but the sub isn't hitting hard. I have the gain set midway and the voltage switch is set at 1.0-8.0 volts since i am using a pioneer premier 680mp headunit with 4v preouts. However when i switch the voltage switch to .1-1.0 volt, the sub hits hard like it should. However i don't want to leave it at this setting since it might destroy my system. any reasons why my sub do not hit hard when the voltage switch is at 1.0-8.0 volts?