Amplify makes your Mac louder than the built-in maximum, with a graphic EQ, 3D surround, and per-app volume.
This installer adds the Amplify app and its audio driver. You'll be asked for your password, and your Mac's sound will restart for a second or two during installation — that's normal.
After installing, click ⚡ in your menu bar and turn Boost on. When asked, allow microphone access — that's how Amplify reads your audio to boost it.