LFE Filter is a single channel filter for easy inserting in your 5.1 Master section. Its filter shape is over 48dB/oct, so you can use cutoff frequencies over 90 Hz (standard) and get much more punch and sound than other solutions can give.
The x.1 Low Frequency Effect channel is not defined as a full range channel. In most cases its sampling frequency is scaled down to 240 Hz so you have to insert an LFE filter in this channel to prevent alias frequencies. The Starplug LFE Filter is designed with pd Quantum-Filter-Technology.