General Settings

Generates a deterministic periodic pink-noise test signal covering 20 Hz to 20 kHz
- Spectral slope: −3 dB/octave (represents typical programme material)
- Band-shaped: 12 dB/oct high-pass at 20 Hz, 24 dB/oct low-pass at 20 kHz
- RMS ≈ −24 dBFS, peak = −6 dBFS (crest factor ≈ 12 dB)
Applies all active filters to the test signal
Warns when filter output exceeds the configured threshold
Suggests gain reduction to bring peak below 0.95 × threshold (leaving a small safety margin)

Threshold setting: The threshold controls the detection sensitivity relative to digital full scale (0 dBFS):

0 dB (default): warn when the filter output reaches or exceeds full scale — the standard safety level
Negative values (−1 to −5 dB): conservative — trigger the warning before reaching full scale, leaving extra headroom.
Positive values (+1, +2 dB): lenient — only warn when the output is significantly above full scale. Use with caution: values above 0 dB allow actual clipping to go unreported

⚠️ Setting the threshold above 0 dB means clipping can occur without any warning.

Important clarifications:

⚠️ Measurement levels are not tested - Clipping warnings are purely about filter processing, not your imported measurements. The test signal is synthetic and independent of measurement amplitude.

⚠️ Phase processing can cause clipping even with flat magnitude responses - Filters with visually reasonable frequency responses can produce temporal peaks exceeding 0 dBFS. This is especially common with:

Phase correction filters combined with other filters (without crossovers)
All-pass filters that only modify phase
Multiple FIR filters with different causality settings

Why this happens: Phase distortion (or correction) shifts frequency components in time, causing them to align constructively at certain moments. Classic example: a square wave with magnitude 1.0 can exceed 1.0 after phase processing, even though the Fourier magnitude spectrum remains unchanged.

Why disable:

May improve performance on slower systems
Removes safety warnings if you’re confident in your gain staging

⚠️ Warning: Disabling removes safety checks. Always test with your actual audio content when clipping detection is disabled.

Warn when phase FIR guard fails

Default: Enabled

When enabled, LinFIR shows a warning toast if the phase correction auto-correction guard exhausted all its attempts without producing a FIR with flat magnitude response.

The auto-correction guard is always active. It automatically raises the minimum/maximum correction frequency (f_min/f_max) in 1/3-octave steps — up to 100 iterations — until the FIR’s magnitude deviation falls within the per-filter tolerance threshold. If every attempt still exceeds the threshold, the guard gives up and (if this warning is enabled) shows a toast.

To resolve the underlying issue, try:

Reducing the phase correction amount
Reducing the Kaiser β parameter (high β clips filter oscillations and directly causes deviations)
Increasing the tap count
Increasing the per-filter tolerance threshold (“Guard Tolerance” in the phase correction filter settings)

The per-filter Guard Tolerance parameter (0.1–15 dB, default 0.5 dB) is set directly in each driver’s Phase Correction settings and in the Global FIR Phase Correction settings.

Disabling this setting

Silences guard-failure toasts only — the guard still runs silently.
May be useful in advanced workflows where you consciously accept the trade-off.

⚠️ Warning: Disabling hides failures silently. Only disable if you understand the implications.

Auto Causal Alignment

Default: Enabled

Automatically optimizes FIR impulse positioning when using multiple FIR filters with causality, based on logarithmic energy distribution analysis.

How it works:

Computes logarithmic energy for each sample
Shifts log values to positive range while preserving relative distribution
Calculates the log-energy ratio before and after the impulse peak
Positions the peak at ratio × n_taps within the FIR window
- Example: 30% log-energy before peak → peak positioned at 30% of FIR taps
- Example: 50% log-energy before peak → peak centered at 50% of FIR taps

Why logarithmic energy:

Gives more weight to weak signal components (pre-ringing, post-ringing) relative to the dominant peak
Compresses dynamic range to better detect energy asymmetry in the impulse response
More robust than simple amplitude threshold methods with complex filter combinations

Activation conditions:

At least 2 FIR filters are active (correction, low-pass, high-pass, or phase filters)
At least one filter has non-zero causality (> 0.0)

Why it’s useful:

Prevents truncation of both pre-ringing and post-ringing artifacts
Adapts positioning to actual signal energy distribution
Handles asymmetric impulse responses from causal filter combinations
Maximizes useful signal capture in the final cropped FIR window

When to disable:

Manual control over impulse positioning is preferred using custom FIR Compensation Delay adjustments
⚠️ Only disable if you understand signal processing and impulse alignment implications - incorrect manual alignment can cause truncation artifacts or loss of filter effectiveness

Show Manual FIR Delay Compensation

Default: Disabled (hidden)
Type: ⚙️ Advanced Setting

Controls visibility of manual FIR delay compensation fields in both driver FIR filters and global FIR correction window.

What it shows:

FIR Offset Delay field in each driver’s FIR filter section
FIR compensation delay field in the global FIR correction window

Purpose: These fields allow fine-tuning of FIR filter impulse alignment by manually adjusting delay compensation. This is primarily useful when:

Auto Causal Alignment is disabled and manual control is needed
Fine-tuning filter timing when FIR ringing characteristics permit adjustments

⚠️ Warning - Advanced Users Only:

This is an advanced feature requiring solid understanding of:

Digital signal processing fundamentals
FIR filter behavior and causality
Impulse response alignment and windowing
Phase relationships in multi-way crossover systems

Incorrect use can result in:

Filter truncation and loss of effectiveness
Audible artifacts (ripples in frequency response)
Degraded time-domain response

Recommendation: Keep this option disabled unless you have sufficient confidence in your signal processing knowledge. In most cases, use:

Auto Causal Alignment for automatic optimal positioning
Time Delay adjustments for primary timing alignment between drivers
Delay Compensation (in IR Management) for microphone positioning corrections

Default Values for New Projects

Configure default settings that apply when creating new projects. These do not affect existing projects.

Sample Rate

Options: 44.1 kHz, 48 kHz, 88.2 kHz, 93.75 kHz, 96 kHz, 176.4 kHz, 192 kHz
Default: 48 kHz

Default sampling frequency for new projects.

44.1 kHz: Compact DSP platforms with limited processing power
48 kHz: Professional audio standard, most DSP platforms
88.2 kHz: High-resolution audio (2× CD rate, relatively uncommon DSP sampling frequency)
93.75 kHz: Hypex DSP platforms (FA123, FA253, FA502, etc.)
96 kHz: High-resolution audio
176.4/192 kHz: Ultra-high resolution - only use when DSP platform specifically requires it (higher CPU load, larger filter sizes)

FIR length (taps)

Range: 32 to 65536 taps
Default: 512 taps

Default number of taps for individual driver FIR filters (low-pass, high-pass, and correction filters).

512-2048 taps: Sufficient for most crossover and correction applications
4096 taps: Typical maximum needed for standard loudspeaker design
8192-16384 taps: Specialized use for subwoofer phase and magnitude correction in very low frequencies
>16384 taps: Rarely needed - primarily for extreme low-frequency correction or research purposes

Trade-offs:

More taps = better frequency resolution and steeper slopes
More taps = higher latency (taps/2 samples for linear-phase filters)
More taps = larger file sizes and more DSP processing required

Global FIR Taps

Range: 32 to 65536 taps
Default: 512 taps

Default number of taps for the global FIR correction filter (applied to the summed system response).

Same considerations as FIR length (taps) apply.

Curve Smoothing

Options: None, 1/48 octave, 1/24 octave, 1/12 octave, 1/6 octave, 1/3 octave
Default: None

Default smoothing applied to frequency response curves in plots.

No smoothing: Shows raw response with all detail
1/48 to 1/24 octave: Subtle smoothing, reveals trends while keeping detail
1/12 octave: Good balance between detail and readability
1/6 to 1/3 octave: Heavy smoothing, shows overall trends only

Adaptive Crossover Smoothing

Options: Enabled, Disabled
Default: Enabled

Controls whether smoothing is adaptively reduced near crossover frequencies to preserve slope visibility.

When enabled:

Smoothing progressively reduces within ±0.5 octave of detected crossover frequencies (LP/HP filters)
Reaches minimum smoothing (1/96 octave) at the crossover frequency itself
Helps visualize the actual filter slopes while maintaining smooth curves elsewhere
Only affects magnitude display curves - does not modify phase, group delay, or filter generation

When disabled:

Uniform smoothing is applied across the entire frequency range
Provides consistency with external measurement tools that use constant smoothing

Note: External measurements with uniform smoothing will show gentler crossover slopes compared to LinFIR’s adaptive mode. This is expected behavior - adaptive smoothing reveals the true filter response near crossovers.

Graph Display Mode

Options: FIR, IIR, FIR+IIR, Drivers/Measurements
Default: FIR

Default graph display mode for new projects.

FIR: Shows FIR filter responses only
IIR: Shows IIR filter responses only
FIR+IIR: Shows combined FIR and IIR responses
Drivers/Measurements: Shows complete processed driver/measurement responses

Keyboard shortcuts: Press F (Filters mode) or D (Drivers mode) to switch quickly.

Phase Display

Options: Unwrapped, Wrapped
Default: Wrapped

Default phase display mode for new projects.

Wrapped: Phase values constrained to ±180°, with discontinuities at boundaries
Unwrapped: Continuous phase values extending beyond ±180°

Note: Group delay is always computed from unwrapped phase; this setting only affects the phase graph display.

Keyboard shortcut: Press U to toggle unwrap/wrap mode.

Remove time of flight rotations

Options: Enabled, Disabled
Default: Disabled

Removes the linear phase component (constant group delay) from phase responses to flatten phase around 0°.

How it works:

Loudspeaker Design: Removes linear delay of Sum curve from all driver responses (or driver’s own delay for single driver)
Room Calibration: Removes linear phase component of each individual measurement independently (no shared reference)
Filters Mode: Removes linear phase component of each individual filter

Use cases:

Loudspeaker Design: Identify phase alignment issues between drivers relative to system response
Room Calibration: Compare phase behavior across room positions without timing offsets

Keyboard shortcut: Press C to toggle time of flight rotation removal.

Reset Application Settings

⚠️ Warning: This action cannot be undone!

Completely reset all LinFIR settings to factory defaults.

What gets reset:

All application settings and preferences
Application cache and UI state
Default values for new projects
Audio device selections
Graph display preferences

What is NOT reset:

Existing project files (your work is safe)

Process:

Save your current project before resetting
Click “🔄 Reset Application Settings” button
All settings restored to factory defaults

When to use:

Troubleshooting configuration issues
Starting fresh with default settings
Clearing corrupted preferences
Removing experimental settings after testing

Keyboard shortcuts

LinFIR Documentation