The main source of information and how to setup is here
For qpaeq, it is recommended you try git versions (listed on the wiki).
(old) Screenshots are available here
Video of equalizing in action (skip to 2:20) here
Here is a list of pros/cons for the pulseaudio equalizer vs the ladspa/mbeq backed equalizers (psyche83's eq. script thus included)
- realtime adjustments
- unlimited bands* (qpaeq dynamically scales the bands to the width of the window)
- higher accuracy
- frequencies are natural (mbeq's frequencies are proportional to the real frequencies we hear in)
*the limit is half the sample-rate of your master sink/sound card. One cannot specify any more useful information beyond that number of bands (theoretical limit).
- general/tradeable presets not implemented yet, slowly being worked on though (server side preset "states" exist though)
cons with a mbeq backed equalizer:
- frequencies (coefficients you specify in control) above it's 1024 hz are ignored
- aliasing occurs because the filter doesn't sample sufficiently, see the bottom two graphics here for a visual description.
- frequencies are proportional to the real frequencies we hear in
cons with psyche83's gui (mbeq backed):
- need to hit apply for changes to take effect (not real-time)
- fixed to 15 bands
Also note that this equalizer is in upstream pulseaudio and will be probably be released in the next official version (whenever that is).