On Sat, Dec 23, 2006 at 05:58:34PM +0100, Pelle Nilsson wrote: > Thanks! Apart from letting me know how to create the AC3 from the > command line if I should need to do that, it also hinted at a standard > recipe for dealing with the LFE channel: Mix all the other channels > into one and apply a lowpass filter with a cutoff frequency of > 150Hz. I will assume that this is a good method for now and look at > the results. This is actually not so good advice. Moving the LF content from the 5.0 signals to the subwoofer may be required in many systems if the 5.0 speakers can't reproduce LF because they are too small. But it should be done at the reproduction end, simply because it depends on the reproduction system. Most 'receivers' can be set up to do this - it's called 'bass management'. In a 5.1 system the subwoofer signal is not the same as the LFE channel. The signal that goes to the subwoofer should be the LFE channel amplified by 10 dB, plus any bass that can't be reproduced by the five main speakers. But the latter can only be decided at the reproduction end. Users that have full range 5.0 speakers will expect the LF in the main channels. The may still want to redirect some of it to the subwoofer, but it should be their choice to do so or not. The LFE channel is meant for effects such as earthquakes and bombs. In a correctly set up system it will also have 10 dB more gain than the other channels. It should not be used for music. Even the center channel has little use - if you calculate the psychoacoustically correct signals for a 5.1 layout, it contributes little. It exists mainly as a dialogue channel for movies. -- FA Lascia la spina, cogli la rosa.
