Well. The LFE channel is fed to the sub woofer so we're talking the same thing. And when any speaker is set to 'small' all frequencies below the crossover setting are then added to the LFE channel which then makes it way to the sub woofer. The sub on its part uses its on Low pass filter which essentially passes frequencies below its setting. So if this setting is maxed out, you're in essence using only the LPF (or crossover) of the AVR only.
The LPF on the sub is useful lets say when you are feeding the L+R channels of the AVR to the Sub and the sub then outputs to your L+R speakers. In this scenario the Sub will filter the frequencies below your sub setting and pass the rest to your main speakers.
Regards,
Navin
The LFE channel is not the only one that is fed to the subwoofer. When you have a 5.1 system with "small" satellite speakers, the following signals get fed to the sub:
1. the ".1" LFE channel - the LFE crossover is applied to this channel
2. The bass component of the 5 satellite channels after the crossover is applied in the AVR's bass management module.
The bass component of the satellite channels never pass through the LFE crossover of your AVR, only the LFE channel is affected. So in effect you can set your satellite crossovers to 200Hz, your LFE crossover to 80Hz and still end up with the frequencies between 80Hz & 200Hz from your satellite channels on the sub.
As per the encoding standards and THX spec, the LFE low pass filter of your AVR should always be set at 120Hz and not changed.
When using an AVR's bass management and with the AVR driving the sub directly, follow these steps for your AVR's setup:
1. Set speaker size to small/large depending on your speakers, but in general this should be set to small unless you have speakers that can handle frequencies below 40Hz or if you are not using a subwoofer. Setting speakers to small lets the AVR do bass management for those speakers, so rather than small/large, it should perhaps be read as bass managed/unmanaged. Setting floorstanders to small with a cutoff frequency of 80Hz would also ensure that you do not have many issues with bass frequency interference between your floorstanders and your sub.
2. Set the HPF crossover frequency of each speaker based on the frequency response of that speaker. Typically when you are using floorstanding tower speakers with a lower -3db cutoff at around 40Hz, you would set the tower speakers to small & set the cutoff frequency to 40Hz. This will ensure that your sub gets used for frequencies below 40Hz. Unless you are using speakers that are not designed for primary use as satellite speakers, this cutoff frequency should be 80Hz or above. Setting this value to a higher frequency with small speakers may help you get more performance out of your speakers as they will not be overburdened with bass frequencies.
3. Set the LPF cutoff filter on your sub to its max value. This feature is useful only if you are feeding full range output to the sub. Adding this LPF to the AVRs bass management will not help in 99% of the cases.
4. Adjust the levels of your sub & speakers from the AVR. On most AVRs, there is a noise function, which allows you to feed white/pink noise to individual channels so that you can adjust their levels. This method is not very accurate w/o a db meter, but if you spend some time and quickly flip through the channels, you can get a reasonably accurate level matching.
5. Set the speaker distances. Start with a tape measure and measure the distance of your primary listening position from each speaker. Set the AVR to accept distances in the smallest increments and enter values with that level of precision. This is only the first step. For the sub, you may need to play with the phase functions, sub location the sub distance value in the AVR to get a accurate time alignment. To get this step done accurately, you will need to use some calibration tones. In a large number of cases, the sub distance will be quite different from the actual distance after you do the final adjustment. Remember that the distances obtained with the tape measure are only a begining point and that the final figures will depend on various other factors.
6. Set up the EQ for each speaker. This is easily done with a spectrum analyzer, doing it by ear requires a lot of past experience and is best left to the experts.
-- no1lives4ever
PS: Please read through batpig's denon to english dictionary and go through the linked audyssey threads on avsforums. Even if your AVR does not have Audyssey, the linked threads on avsforums will help you understand and clear up these concepts as applied to denon avrs.