Anybody know anything about subwoofers?

Just found this http://support.alpine-usa.com/products/documents/OM_iDA-X303_EN.pdf

its shows that your head unit has a subwoofer ON/OFF setting.

1. press and hold IMPRINT for 2 seconds to activate audio selection.

2.Turn the double action encoder to select the SUBW mode then press enter.

3.Turn the double action encoder to select Subwoofer ON/OFF then press enter.

in the same area of the settings are the subwoofer volume settings and output settings and what not too.

Also I see there is a SYS1 setting and a SYS2 setting ....I read somewhere that one of the settings forces the subwoofer to maintain once specific volume even when the volume is raised on the headunit itself.

there is alot of other info in that link I posted also....hopfully it is of some use ( you probably already have the same info in your manual) but I figured it wouldnt hurt to mention it and give you a couple other things to look into on top of what I and others have already mentioned.