LPF for LFE

ls7z06

I have this on my Onkyo receiver menu. I have it set to it's max of 120Hz simply because somebody on a forum said that was where it should be. Can anybody explain what this setting is and what it does? I think it stands for Low Pass Filter for low frequency effect. I have all of my other speakers set to cut over at 80Hz. Thanks much.

kuntasensei

It's exactly what you said - a low pass filter for JUST the LFE channel (not redirected bass for the other channels, which is controlled by the low pass filters that are part of each channel's crossover). The only function this setting really has is for compliance with THX spec'd subwoofers that are designed specifically to not play content above 80Hz. The LFE channel by its nature is brickwall filtered on a digital level at 120Hz in the DTS and DD bitstreams, which is why you should set LPF of LFE to 120Hz - so you aren't removing any audio above 80Hz that might have been placed in the LFE channel by the original audio mixer.

That said, audio mixers rarely place any direct content above 80Hz in the LFE channel to prevent localization of the subwoofer... but there are, however, harmonics above 80Hz that lend a perceived tone to the sub-80Hz material in the LFE channel, and you would lose that by using anything other than 120Hz for LPF of LFE. Whether you would notice the difference depends on your ears and your subwoofer, but the 120Hz setting ensures that you are passing the entire LFE channel to your sub.

ls7z06

That was very, very helpful. I get it now. Thanks very much!