if it's the subwoofer feature, then you should be able to press the multi-control, go to the settings tab (or w/e it's called), and then scroll through to the subwoofer on/off and either press in on the multi key or press it left/right (not sure on that model) to turn it on/off or select it.
should give you an idea.
i have an 860mp so i'm not 100% sure.