• You have: Pulseaudio, and an audio output device (sink).
• You want: Change the frequency response of exactly this audio output device.

Equalizer curve

Use qpaep to adjust the equalizer curve.

Pulseaudio setup

By default, the Pulseaudio equalizer will only attach to the default sink. If you want the equalizer on a specific sink, add an equalizer module using:

pactl load-module module-equalizer-sink sink_master=$SINK

where $SINK is the sink name obtained from pactl list sinks.