Bruno, that setting affects only the LFE channel which contains low frequency effects occasionally present in movies. It isn't the crossover(80Hz or whatever)between the sub and speakers on regular material(movies or music)channels. The LFE channel extends to 120Hz, but in practice little or nothing above about 80Hz is mixed into it. Some want to set the filter to 120Hz in case something useful is occasionally up there, others say that the only thing there is some random noise which could be lessened with a 80Hz setting. Not a matter of much concern either way.
