Apply LADSPA filter to only one channel of multichannel output with Alsa and PulseAudio

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http://askubuntu.com – I want to apply a filter, specifically SWH's glame-bandpass-iir, to only one of several output channels. I want unfiltered output to go to the front, rear and LFE channels with bandpass filtered output for the center channel. I'm assuming that this needs to be done with Alsa's /etc/asound.conf but I cannot understand the documentation well enough to figure out how. If there is a better way, via PulseAudio, Jack or whatever, I'm open to whatever works. Thanks. (HowTos)