macOS doesn't have a system-wide parametric EQ. So I built one in a day.
Built at 04:57 in Bavaria, listening to Opera by Ballarak on a Teufel Concept E 5.1. That's the only explanation you need for why this exists.
A native macOS system-wide parametric EQ with a real-time Pre/Post spectrum analyzer. No virtual audio drivers. No Electron. No paywall. Just Swift, CoreAudio, and a CATap doing what they should've always done.
The install process was a hassle. The UI was tiny and fiddly. Half of what I needed was behind a "Pro" paywall. Then my Mac crashed and took the software down with it. That's the actual reason iQualize exists.
eqMac uses a virtual audio driver. iQualize uses a CATap — Apple's native system audio tap introduced in macOS 14. No driver to install. No driver to break. No driver to fight with Bluetooth. It just works.
- macOS 14.2+ (Core Audio Taps API)
- System Audio Recording permission
Grab the latest .dmg from Releases, open it, and drag iQualize to Applications.
iQualize is signed with an ad-hoc signature, not a Developer ID certificate, and it isn't notarized. macOS puts a quarantine flag on anything downloaded from the web, and for an app it can't verify that shows up as a malware warning on first launch. Nothing is wrong with the download — Gatekeeper is reporting that the app hasn't been through Apple's notarization service, which requires a paid developer account.
The fastest fix is one command, which clears the flag so none of the warnings below appear:
xattr -dr com.apple.quarantine /Applications/iQualize.appThen open it normally. If the .dmg itself won't mount, clear the flag on the download first: xattr -c ~/Downloads/iQualize-*.dmg.
The GUI route works too, but it takes four screens and the first one looks like a dead end — worth knowing what's coming.
1. Open iQualize. You get this. There is no "open anyway" here; that is expected. Click Done — not Move to Trash.
2. Go to System Settings → Privacy & Security, and scroll to Security. The blocked app now appears with an Open Anyway button. This row only shows up after step 1, which is why the order matters.
3. Confirm. macOS asks a second time, more sternly, and may ask for your password. Click Open Anyway.
4. Allow audio capture. This one is iQualize asking, not Gatekeeper. The EQ cannot work without it — it is the permission that lets the app see system audio at all.
Older macOS versions expose the same Open Anyway option under System Preferences → Security & Privacy → General. Screenshots are from macOS Tahoe; Apple rewords these dialogs between releases.
If you ever see "iQualize is damaged and can't be opened" instead, that is a different problem — a genuinely broken signature rather than a missing one. That was #115, fixed in 0.45.0; report it if a current release does this.
bash scripts/install.sh # builds, signs, installs to /Applications
open /Applications/iQualize.app- No arbitrary limit on the number of EQ bands — the practical limit depends on your Mac's available processing resources. Editable frequency (20 Hz – 20 kHz), gain, and bandwidth per band
- Q / Octave display toggle — switch between Q factor and octave bandwidth globally (Q is the default, octaves for musicians who think in bandwidth)
- 7 filter types per band: Bell (parametric), Low Shelf, High Shelf, Low Pass, High Pass, Band Pass, and Notch
- Biquad frequency response curve using Audio EQ Cookbook formulas, rendered as a translucent backdrop behind EQ sliders
- Per-band ghost fills, anchor dots with dB labels, and split boost/cut composite fill
- Axis labels and detailed frequency/dB grid overlay
- Adjustable max gain range: ±6, ±12, ±18, or ±24 dB — or auto-scale to fit the current curve (up to ±24 dB)
- Input gain (±24 dB) — pre-EQ level control for proper gain staging
- Output gain (±24 dB) — post-EQ level control, applied before the peak limiter
- In/Out dB can be shared globally across all presets, or set per-preset — toggle in Settings → General (see Presets and Settings below)
- Dynamic peak limiter (AUPeakLimiter) — prevents digital clipping at 0 dBFS
- Only changed parameter values are written to the audio unit — no audible glitches on slider drags
- Add bands with + buttons on either side of the EQ — new band copies the leftmost or rightmost band
- Right-click context menu: Add Suggested Band finds the largest frequency gap and inserts a new band at the geometric midpoint
- Delete, or reorder via the right-click context menu (Move Left/Right)
- Minimum 1 band, no maximum
- Built-in presets: Flat, Bass Boost, Vocal Clarity, Loudness, Treble Boost, Podcast, Techno, Deep House, Hard Techno, Minimal, American Rap, German Rap, Luzifer's Void, DEADBEEF, 0xDEADBEEF
- Create, rename, overwrite, and delete custom presets
- Built-in presets can be deleted too (except Flat) if you don't want them cluttering your picker — bring a deleted one back anytime from the Preset Browser's iQualize tab
- Built-in presets auto-fork when edited (non-destructive)
- In/Out dB gain can be stored per-preset (default) or shared globally across all presets — see Settings → General
- Unsaved changes indicator (asterisk in title)
- Import/export as
.iqpresetJSON files with batch import and overwrite protection — also accepts AutoEQParametricEQ.txt/GraphicEQ.txtand OPRAeq_info.jsonfiles - Preset Browser: an OPRA tab to search and import community headphone/IEM EQ profiles directly from the OPRA database, and an iQualize tab to restore any built-in presets you've deleted
- Quick switching from the menu bar or EQ window picker — both use the same native preset picker, with Favorites, Built-in, and Custom sections
- Favorite presets (star icon, or ⌥-click a preset) to pin them to the top of the picker for one-click switching
- Pin a preset to an output device (pin button in the EQ window toolbar, or from the menu bar) — it's recalled automatically whenever that device becomes the active audio output, including at launch
Presets are .iqpreset files — plain JSON:
{
"bands": [
{ "bandwidth": 1.0, "filterType": "parametric", "frequency": 80, "gain": 5 },
{ "bandwidth": 1.2, "filterType": "lowShelf", "frequency": 200, "gain": -3 }
],
"id": "CDE9BB8A-12A5-420C-9619-2790E20030D5",
"isBuiltIn": false,
"name": "My Preset"
}Each band: frequency (Hz, 20–20000), gain (dB), bandwidth (octaves, 0.05–10 — 1.0 = one octave ≈ Q 1.41), filterType (one of parametric, lowShelf, highShelf, lowPass, highPass, bandPass, notch — defaults to parametric if omitted).
Presets may also carry inputGainDB and outputGainDB (dB, optional — omitted or absent means 0 dB, and they're only applied when In/Out dB is in per-preset mode; see Settings → General).
- Full undo/redo for all EQ modifications (gain, frequency, bandwidth, reorder, add, delete)
- Slider drags coalesced into single undo actions
- Cmd+Z / Cmd+Shift+Z
- Click a band or drag its slider to select it (accent-colored border indicator)
- Arrow Up/Down to adjust gain (±0.5 dB per step)
- Arrow Left/Right to adjust frequency (semitone steps)
- Tab / Shift+Tab to cycle between bands
- Scroll wheel over sliders to adjust gain
- Scroll wheel over frequency/Q inputs to adjust those values
- Cmd+B — toggle Bypass EQ (works from the EQ window or menu bar)
- Cmd+, — open Settings
- Rapid adjustments coalesced into single undo entries
- Open iQualize — first item in the menu for quick access
- Option+click the menu bar icon to open the EQ window directly (skips the menu)
- Presets submenu with checkmarks and active preset name in parent item — changes sync to the EQ window in real time
- Bypass EQ toggle (Cmd+B) — pass audio through unprocessed; while bypassed, the Post-EQ spectrum line and its color/fill controls are hidden/disabled (post-EQ would otherwise just mirror pre-EQ)
- Current output device display, with a pin/unpin item to remember a preset for that specific device
- Help… (Cmd+?) — opens an in-app Help window rendering the README's Features section, with a "View latest on GitHub" link
- About iQualize — shows version and a "View on GitHub" button that opens the project page in your default browser
Accessible via the gear icon in the EQ window, the Settings item in the menu bar, or Cmd+,.
- Audio: Peak Limiter toggle, Max Gain range (±6/12/18/24 dB), Auto Scale toggle
- Display: Pre-EQ / Post-EQ spectrum toggles, per-spectrum line color picker, per-spectrum Fill toggle with its own color picker, reset buttons to return to the dynamic system colors, Q / Octave bandwidth display toggle
- General: Theme (Auto / Light / Dark), Hide from Dock toggle, Start at Login toggle, Share In/Out dB across all presets toggle, Install Command Line Tool button
- Dual real-time spectrum analyzer: pre-EQ (raw input) and post-EQ (processed output)
- Independent toggle checkboxes for pre-EQ and post-EQ display
- 2048-point FFT via Accelerate vDSP with Hann windowing and log-frequency binning
- Catmull-Rom spline rendering with peak hold lines
- Lock-free double-buffered audio-to-UI transfer, so 60fps UI updates never block on the audio thread
- Customizable line and fill colors per spectrum (Settings → Display) — defaults to cyan for pre-EQ, orange for post-EQ, both adapting to Light and Dark appearance; reset returns to the dynamic system color
- Per-spectrum fill toggle (off by default for pre-EQ, on for post-EQ) with its own color, independent from the line color
- Post-EQ spectrum auto-hides when EQ bypass is active (post-EQ would otherwise just mirror pre-EQ)
- Spectrum toggle states, fill toggles, and color choices persist across app restarts
- L/R balance slider in the bottom bar, centered by default
- Snap-to-center with double-click reset
- Applied as per-channel gain in the audio render callback
- AirPods hand off automatically between your Mac and iPhone mid-playback (Apple Continuity), the same as any other app — no need to quit iQualize or manually switch output first
- Automatic output device switching and reconnection
- Apps launched after iQualize is already running get picked up into the EQ automatically, no restart needed
- Calls (FaceTime, WhatsApp, Discord, Zoom, phone calls) play at normal volume: an app that's actively using the microphone is passed through untouched for the duration of the call, then picked back up into the EQ when the call ends. Call audio skips the EQ while the call is live — macOS would otherwise duck the call's voice far below normal
- Sleep/wake handling — pauses on sleep, resumes on wake
- Window state and all settings persist across launches
- Codesigned for stable TCC permissions across rebuilds
- Built with Swift Package Manager — no Xcode project needed
Control a running iQualize instance from the terminal — skip the menu bar entirely, and script iQualize with it: Shortcuts, launchd jobs, keyboard-shortcut launchers, etc.
Setup (one-time): open iQualize → Settings (Cmd+,) → General → "Install Command
Line Tool". This prompts for your admin password once and adds iqualize to your
PATH. Open a new Terminal window afterward — a window that was already open won't
pick it up. (Building from source instead? scripts/install.sh symlinks it automatically, no
button needed.)
iqualize # same as `iqualize status`
iqualize status # app version, bypass state, active preset, gain, balance, output device
iqualize version # just the app version and build commit
iqualize presets # list all presets (* = active, ♥ = favorite)
iqualize preset "Bass Boost" # switch the active preset by name or ID
iqualize bypass [on|off|toggle]
iqualize gain input [<dB>] # omit the value to read the current one
iqualize gain output [<dB>]
If iQualize isn't running, the CLI launches it and retries for about 5 seconds before
giving up. If Terminal still says command not found after installing, double-check
you opened a new window/tab, and that /usr/local/bin is on your PATH (echo $PATH).
For the long version — why CATap, what fought back, and how the audio graph came together — read the blog post: Building iQualize - A System-Wide EQ That Doesn't Suck.
iQualize uses Core Audio Taps (CATap), introduced in macOS 14.2, to intercept system audio without a virtual audio device. Virtual devices (like BlackHole) create a secondary audio path — you lose system volume control, break some DRM-protected audio, and add latency. CATap captures the audio stream directly from the HAL and processes it before it reaches the output device.
The tap and IOProc run in a small helper process (iQualizeCapture), separate from the app that renders the processed audio. A process that both holds an active tap and drives the render stream on the same output device gets treated by coreaudiod as non-preemptible — which silently blocks AirPods from auto-switching between your Mac and iPhone (Apple Continuity). Splitting tap-ownership from rendering into two processes keeps that path free, so Continuity handoff works the same as it would with any other app.
Apps in a call are excluded from the tap while the call is live. macOS ducks all "other audio" on the output device during a voice session but exempts the session owner's own stream — and a tapped call re-rendered through iQualize counts as other audio, so the OS ducked the call voice itself by ~18 dB (#131). The helper watches for processes running both audio input and output (the signature of a call — mic-only processes like dictation stay in the tap), removes them from the live tap's exclusion list, and re-includes them when the mic is released. Excluded call audio plays directly at the session-owner volume; the EQ skips it for the duration of the call.
flowchart LR
subgraph capture["iQualizeCapture (helper process)"]
direction TB
apps["App Audio"] -->|CATap| aggregate["Tap-only Aggregate Device"]
aggregate -->|IOProc| shm[("Shared Memory<br/>Ring Buffer")]
end
subgraph main["iQualize (main process)"]
direction TB
source["AVAudioSourceNode"] --> eq["AVAudioUnitEQ<br/>(parametric EQ)"]
eq --> gain["Output Gain Node"]
gain --> limiter["AUPeakLimiter"]
end
shm -->|CaptureClient| source
apps -.->|muted by tap| device["Output Device"]
calls["Call Apps (mic active)"] -->|"excluded from tap, play direct"| device
limiter -->|AVAudioEngine outputNode| device
The shared-memory ring buffer decouples the helper's real-time IOProc callback from the main app's AVAudioEngine pull model — no locks in the audio thread, no glitches on slider drags. If the helper process ever dies unexpectedly, the main app detects it and stops cleanly rather than leaving audio in a broken state.
iQualize captures audio at the tap's native sample rate; AVAudioEngine's output node converts it to whatever rate the current output device needs, so playback stays correct across device switches. Bluetooth sends stereo (2ch) only — SBC, AAC, and aptX all max out at 2 channels. If your speaker system supports 5.1 — a Teufel Concept E via USB, say — the hardware handles channel routing and upmixing (Dolby Pro Logic II etc) on its end.
Huge thanks to @nordicdata (Gary) for the detailed, well-written bug reports and feature requests — a lot of the fixes and improvements in the changelog exist because he took the time to file them properly.
The Preset Browser's headphone and IEM EQ profiles come from the OPRA project — Open Profiles for Revealing Audio, an open, community-maintained directory of product information and EQ compensation curves. OPRA's data is licensed under CC BY-SA 4.0; each imported profile credits its original author in the browser.
I build tools that shouldn't need to exist.