BookshelfBar: macOS menu bar app for KEF speakers

A native macOS menu bar app for KEF wireless speakers (LSX II LT, LSX II and the rest of the W2 platform), with a fix for common problems, including:

• Volume surge on wake: over USB, the speakers can wake at full volume. BookshelfBar wakes them silent and fades in.
• Speakers that wake right back up: with Wake On set to USB audio, any app holding a stream open (even paused Spotify) wakes them seconds after you turn them off. BookshelfBar lets them sleep.
• Output switching away: macOS can move audio off the speakers while they reconnect. BookshelfBar moves it back.

Not affiliated with KEF.

Features

• Control: power, input, volume and mute, plus desk/wall mode, bass extension, treble, balance, auto-standby, wake source and maximum volume.
• Smooth Start: wakes the speakers before audio plays, guards the moment the speaker reconnects over USB, and fades in from silence. The volume can be set while they're asleep; it applies when they fade back on.
• Keep Awake With Screen: optional. The speakers stay on while the Mac's screen is on and go to standby when it turns off, if nothing is playing.
• Volume curve: shape the slider so everyday listening levels get the most travel.
• Live: reflects changes made with the remote, top panel or KEF Connect.
• Native and light: SwiftUI with system controls and SF Symbols, no polling, and no network connection at all while the speakers are in standby and the menu is closed.

Install

Requires macOS 26 or later.

Homebrew:

brew install --cask yeutterg/tap/bookshelfbar

Or download BookshelfBar-<version>.dmg from Releases, open it, and drag BookshelfBar to Applications.

Opening an app that isn't notarized

BookshelfBar isn't notarized by Apple yet, so the first time you open it macOS says it can't verify the app. To open it anyway:

1. Open BookshelfBar from Applications. When macOS says it can't be opened, click Done.
2. Open System Settings → Privacy & Security and scroll down to Security. Next to "BookshelfBar was blocked to protect your Mac", click Open Anyway, then confirm with your password or Touch ID.
3. Click Open Anyway once more in the dialog that follows. macOS remembers this, so you only do it once per version.

Or, in Terminal, remove the download quarantine and open it normally:

xattr -dr com.apple.quarantine /Applications/BookshelfBar.app

Only do this for apps you trust. The source is all here, and you can build it yourself instead.

Quick start

1. Connect the speakers. Plug the primary speaker into your Mac with USB‑C for USB audio. The Mac and the speakers need to be on the same network.
2. Open BookshelfBar and click Allow when macOS asks for Local Network access. BookshelfBar uses it to find and control your speakers.
3. Pick your speakers. If there's more than one pair on your network, Identify wakes a pair briefly so you can tell which is which. You can switch later under About → Change Speakers…
4. Play. Choose your speakers (e.g. "LSX II LT") in the macOS Sound menu. Smooth Start is on by default: they wake silent and fade up to your volume.
5. Optional:
   • Turn on Keep Awake With Screen to have the speakers follow your display.
   • Open Sound for the volume curve, desk/wall mode, bass extension, treble, balance and the speakers' power settings.
   • If macOS asks whether BookshelfBar may record system audio, that's only so the speaker animation plays while sound is actually coming out. Nothing is recorded. Saying no just keeps the animation still.

Suggesting improvements

Found a bug or have an idea? Please open an issue. Pull requests are welcome too, but for feature requests and bug reports we prefer an issue first, so we can talk it through and throw our agents at it.

Build it yourself

swift build                 # library, CLI and app
swift test                  # unit tests
scripts/bundle.sh           # builds build/BookshelfBar.app
open build/BookshelfBar.app

On first launch macOS asks for Local Network access, which the app needs to find and control the speakers.

kefctl

A command-line tool on top of the same library, handy for scripting and debugging:

swift run kefctl discover
swift run kefctl info
swift run kefctl vol 30
swift run kefctl source usb
swift run kefctl events          # live changes
swift run kefctl usb             # KEF USB audio device state on this Mac

How it works

The speakers expose a local HTTP API on port 80, the same one KEF Connect uses. Since firmware 2.0, writes to settings (DSP, power options) must be signed with the speaker's HMAC_SHA256_AES256 scheme; KEFKit implements it. The USB port is a plain USB Audio Class device, so all control goes over the network.

When a sleeping speaker starts playing over USB, it wakes, drops off the USB bus about 3 s later, and comes back 1–4 s after that as a new audio device. Sometimes it returns at full USB gain before macOS restores the saved volume, and sometimes macOS moves output to another device and doesn't move it back. docs/RESEARCH.md has the measurements, the API notes and the design decisions.

Layout

Credits

Request signing is adapted from tkelkermans/KefSleepSync (0BSD). The API notes draw on EvotecIT/homeassistant-kef, N0ciple/pykefcontrol, hilli/go-kef-w2 and roberdorfer/kef-lsx-volume. KEF, LSX and Uni-Q are trademarks of GP Acoustics. Speaker artwork is rendered from KEF's product models.

License

MIT

Releasing

Push a tag like v0.2.0. The release workflow tests, builds a universal app, signs and notarizes it when the secrets below are set, publishes a GitHub release, and updates the cask in yeutterg/homebrew-tap. Repository secrets:

Without the signing secrets the workflow still builds a DMG, but it isn't notarized. Locally: VERSION=0.2.0 scripts/release.sh (set SIGN_IDENTITY and the NOTARY_* variables to sign and notarize).