Not familiar with FLE.
LFE = low frequency effects. Basically the subwoofer for home theater surround sound.
HPF = High pass filter. HPF can be a small capacitor put in the signal path at the input of an amplifier which filters out low frequencies. This relieves the midrange drivers from having to reproduce lower frequencies. This can also be a setting on a surround receiver.
LPF = Low pass Filter. Filters higher frequencies typically for subwoofers.
