FIRDesign 1.0
The FIR filter designer for loudspeakers and rooms
A linear- and minimum-phase FIR filter designer, in the spirit of rePhase. Design a correction by hand and from measurements; see exactly what it does across magnitude, phase, group delay and impulse; then export a filter for your convolution engine.
Native macOS, Windows & Linux. Self-contained — nothing else to install.
Designing filters
- Three independent channels. A filter is built from parametric bands (each carrying both magnitude and phase), a magnitude correction curve, and a phase correction curve — combined into one FIR.
- Parametric bands in banks of 16, with types peak, low/high shelf, low/high pass, all-pass, phase EQ and linearize; drag on the chart or type exact values; per-bank gain range (±6 / ±12 / ±24 dB).
- Phase modes. Linear, Minimum, or Intermediate — a continuous blend via α.
- Synthesis windows. Auto (picks Blackman for steep filters, Hann otherwise), plus Hann, Blackman and Kaiser with adjustable stopband attenuation.
- Fidelity-aware auto-centering. Finds the minimal latency that still reproduces the design faithfully — including steep low-frequency filters — or set centering by hand.
- Full control. Sample rates 44.1–192 kHz, tap counts 1024–65536, selectable optimization passes, and output gain with one-click Normalize.
Measuring & correcting
- Measurement import. Load
.frdmeasurements with smoothing and a level offset; impedance-looking traces are detected and refused. - Targets. Flat, a tilt/slope, an imported curve, or a built-in house-curve builder (bass boost, treble cut, slope).
- Auto-EQ (magnitude). Fits the correction to your target — as a smooth curve or as bands — with sensible max-boost / max-cut limits and warnings when a limit is reached.
- Excess phase. Removes excess phase (crossover, driver, delay) beyond minimum phase, always gated by per-frequency measurement reliability, with a clear verdict.
- Verify loop. Load an after-correction measurement to overlay the real result against the baseline, plus a delta-prediction that tracks further edits without double-correcting.
Seeing what you did
- Six hand-drawn, high-resolution charts (log-frequency): magnitude, phase, group delay, impulse and error — with legend, hover read-out, a shared crosshair, zoom and masking.
- Audibility-graded Design Check. Continuously grades the filter and flags issues by audibility — a green "OK" when there's nothing to worry about, with notes like "≈45 dB below peak, likely inaudible" so warnings stay meaningful.
Output & projects
- Export the impulse response as WAV, raw (headerless float), or text (rePhase-style, one coefficient per line).
- Projects (
.firproj) save and restore the full design. - Undo / redo with coalescing history (a continuous fader drag collapses to one step).
Help & expert control
- Comprehensive in-app help — searchable, cross-linked topics, opened from the toolbar ?, F1, or contextual ? buttons. Rendered natively, so it adds nothing to the download.
- Expert panel exposes a few normally-baked-in judgment-call constants (auto-centering tolerance, auto-window steepness, Auto-EQ Q cap), saved per project.
- Generous-but-sensible value limits throughout, so a stray entry can never push the engine into nonsense.
Platforms & installation
Native, self-contained installers — a trimmed OpenJDK and OpenJFX are bundled, so there's nothing else to install.
- macOS — Apple Silicon (arm64) + Intel (x86_64),
.dmg - Windows — x64,
.msi/.exe - Linux — arm64 + x86_64,
.deb/.rpm/.AppImage
Try, then unlock
FIRDesign installs once and runs as a trial: every feature works except project save and impulse export, which are shown but locked, and the title shows "(Trial)".
Buy the full version — $39, one-time — and you receive a license key. Paste it into Activate… (or load it from the file you were sent) and FIRDesign verifies it on your machine. No login, no server, no phone-home — activation is fully offline, and your copy is "Licensed to you". Restart to unlock everything.
Design your first filter today
Try every feature free, then unlock with a one-time $39 license.