#25 foo_input_apt-x100 LFE filter for 5 channel files

[Anonymous]

I think the filter should be a Butterworth rather than a Linkwitz-Riley filter.
The dts studio mixing guide says **The subwoofer information is
filtered with a steep lowpass at 80Hz and is added to each of the surround channels. ... Upon playback,
each surround channel is crossed over with the subwoofer at 80Hz.

[Maxim V.Anisiutkin]

Linkwitz-Riley is in some sense "squared" Butterworth because of advantage of -6 dB at crossover frequency (instead of -3 dB for Butterworth). Could you give an exact formula for the filter please?

[Gunter]

Linkwitz-Riley has its merrits for speaker crossovers. But the roll-off happens over wider frequency range.
What dts is doing is not a crossover thing but transporting a separated channel in the surround channel. For this purrpose a filter with a flat response in the passband is preferred.
The dts 5channel LFE processing is not well documented therefore I do not have the spec for the filter.
However, I might be able to do some measurements with a dts player to estimate the order of the filter.