How/What to set the cutoff frequency AC3Filter?

[OpTicaL]

My current setup is Windowx XP Pro XP3 with Creative X-Fi Fatality and Altec Lansing 5100 (5.1) and have a question on what to set the crossover frequency to.

First off, what's the difference between "cutoff" frequency and "crossover" frequency?

I'm using AC3Filter 1.63b to decode surround sound audio with bass redirection option checked and set to 120 "cutoff" frequency.

Creative's software comes with a program called THX console which has the "crossover" frequency set to 80Hz 'THX'.

Should my "cutoff" frequency be set to 80 in AC3Filter as well?

Here are the specs for my speakers:

TOTAL CONTINUOS POWER - 73 Watts RMS

* Front Speakers: 7 Watts/Channel @ 4 ohms @10% THD @ 100-22000 Hz 2 Channels Loaded
* Rear Speakers: 7 Watts/Channel @ 4 ohms @ 10% THD @ 100 - 22000 Hz 2 Channels Loaded
* Subwoofer: 23 Watts @ 4 ohms @ 10% THD @ 30 - 85 Hz Single Channel Loaded

 

[jinjuku]

Cross over can be thought of a baton handoff between speakers. One speaker hands X audio range Y speaker handles the next audio ranged.

Cutoff does what it sounds like.

 

[MDS]

The 'cutoff' frequency is the highest frequency from the LFE channel (the '.1') that should be sent to the subwoofer. The LFE channel can go as high as 120 Hz so that is the default setting for the cutoff frequency. If you only wanted really low bass in the LFE channel to go to the sub, you could set it lower but then you'd be cutting off some of the frequencies in the case of an LFE channel that does contain information above the frequency you set.

The xover frequency is the frequency that is sent to the sub from each of the other channels and is not related to the cutoff frequency. 80 Hz is the THX recommended value for most setups.

 

[OpTicaL]

Thanks for the explanation guys, I have having a read over here, but it doesn't talk about cutoff freq.

The 'cutoff' frequency is the highest frequency from the LFE channel (the '.1') that should be sent to the subwoofer. The LFE channel can go as high as 120 Hz so that is the default setting for the cutoff frequency. If you only wanted really low bass in the LFE channel to go to the sub, you could set it lower but then you'd be cutting off some of the frequencies in the case of an LFE channel that does contain information above the frequency you set.

The xover frequency is the frequency that is sent to the sub from each of the other channels and is not related to the cutoff frequency. 80 Hz is the THX recommended value for most setups.

How do I know how high or low I should set my cutoff freq. to?