The Low Pass Filter is applied to Left/Right inputs (Not LFE). This setting allows you to select the frequency (points at which the filter starts) and order of the Low Pass filter. (The order of the filter refers to how steep the roll of it is, each additional order noted is another 6dB of roll off per octave, 1st order is 6dB, 2nd order is 12dB, etc.) These settings depend on how low your main speakers play. It is often best to set to bypass and use your receiver/ preamp’s bass management settings so there is no overlap or missing information between the main speakers and the subwoofer.