PulseEffects - Limiter, compressor, reverberation, stereo equalizer and auto volume effects for Pulseaudio...
FxSound - Clearer Sound for Your PC. The new FxSound boosts your sound quality, volume, clarity and bass.
Equalizer Pie - Equalizer Pie is a free audio manipulation application for OS X.
Equalizer APO - A system-wide equalizer for Windows 7 / 8 / 8.1 / 10 with channel remapping/copying capabilities
JamesDSP for Linux - An audio effect processor for PipeWire and PulseAudio clients.
Boom 3D - Audio enhancer with 3D surround sound