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.
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)
- Screen & System Audio Recording permission
Grab the latest .dmg from Releases, open it, and drag iQualize to Applications.
iQualize is unsigned. Apple charges $99/year for a developer certificate. If macOS blocks the app, run:
xattr -dr com.apple.quarantine /Applications/iQualize.appbash install.sh # builds, signs, installs to /Applications
open /Applications/iQualize.app- Up to 31 bands with editable frequency (20 Hz – 20 kHz), gain, and bandwidth
- 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
- Accurate 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
- Catmull-Rom spline interpolation connecting slider knob positions (dashed gray line)
- 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
- Dynamic peak limiter (AUPeakLimiter) — prevents digital clipping at 0 dBFS
- Smooth, glitch-free parameter updates — only changed values are written to the audio unit
- 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, reorder via drag-and-drop or right-click context menu (Move Left/Right)
- Minimum 1 band, maximum 31
- Built-in presets: Flat, Bass Boost, Vocal Clarity, Loudness, Treble Boost, Podcast, Techno, Deep House, Hard Techno, Minimal, American Rap, German Rap
- Create, rename, overwrite, and delete custom presets
- Built-in presets auto-fork when edited (non-destructive)
- Unsaved changes indicator (asterisk in title)
- Import/export as
.iqpresetJSON files with batch import and overwrite protection - Quick switching from the menu bar or EQ window picker
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).
- 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 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
- Rapid adjustments coalesced into single undo entries
- Open iQualize (Cmd+,) — 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
- Bypass EQ toggle (Cmd+B) — pass audio through unprocessed
- Peak Limiter toggle
- Hide from Dock toggle — run as a menu bar-only app
- Start at Login toggle — launch automatically when you log in
- Current output device display
- About iQualize — shows version info
- 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
- Smooth Catmull-Rom spline rendering with peak hold lines
- Lock-free double-buffered audio-to-UI transfer for glitch-free 60fps updates
- Monochrome white/gray spectrum layers with z-ordered rendering; blue EQ response curve is the only colored element
- Spectrum toggle states 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
- Automatic output device switching and reconnection
- 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
iQualize uses Core Audio Taps (CATap), introduced in macOS 14.2, to intercept system audio without a virtual audio device. Virtual devices (like BlackHole or eqMac's driver approach) 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, processes it in-process, and sends it to the output device.
┌─────────────────────────────────────────────────┐
│ macOS Audio Server │
│ │
│ App Audio ──┬── Output Device (muted by tap) │
│ │ │
│ └── CATap ──► iQualize IOProc │
│ │ │
│ ▼ │
│ Ring Buffer │
│ │ │
│ ▼ │
│ AVAudioSourceNode │
│ │ │
│ ▼ │
│ AVAudioUnitEQ │
│ (parametric EQ) │
│ │ │
│ ▼ │
│ Output Gain Node │
│ (AVAudioUnitEQ, 0 bands) │
│ │ │
│ ▼ │
│ AUPeakLimiter │
│ │ │
│ ▼ │
│ Output Device │
└─────────────────────────────────────────────────┘
The ring buffer decouples the real-time IOProc callback from AVAudioEngine's pull model. Parameter changes are written atomically — no locks in the audio thread, no glitches on slider drags.
iQualize detects the output device's sample rate and converts internally so the audio plays back correctly regardless of what device you're on. Bluetooth sends stereo (2ch) only — SBC, AAC, and aptX all max out at 2 channels. If your speaker system supports 5.1 (e.g. Teufel Concept E via USB), the hardware handles channel routing and upmixing (Dolby Pro Logic II etc) on its end.
I build tools that shouldn't need to exist.