Overview

LinFIR is a professional audio software tool designed for precise FIR (Finite Impulse Response) and IIR (Infinite Impulse Reponse) filter design, tailored specifically for loudspeaker crossovers and frequency response correction. The application provides comprehensive control over both magnitude and phase response characteristics, enabling engineers and enthusiasts to craft high-quality audio filter solutions.

Design Philosophy

LinFIR is designed to be both a filter creation tool and a DSP-faithful system simulator. It shows what the filters will actually do when applied to your measurements, not an idealized version.

What You See Is What You Get: LinFIR operates with real DSP constraints—impulse timing, causality, delay, phase rotation, and resampling effects all matter. The application does not silently recenter impulses or adjust phase for prettier graphs. What is displayed is what a real DSP would produce.

This approach requires some understanding of signal processing fundamentals, but LinFIR automates most technical decisions under the hood to keep the workflow practical. The trade-off is that results may sometimes look less “clean” than in tools that abstract away these constraints, but they are physically accurate and predictable.

Different by Design: LinFIR does not replicate the workflows or interface conventions of other tools. The internal DSP-like architecture drives both the workflow and presentation. This is intentional, the goal is to bring a time-domain perspective into DIY loudspeaker and room-correction work, not to replace existing approaches.

Understanding what LinFIR shows and why helps avoid confusion and makes the tool more effective for its intended purpose.

Dual Operating Modes

LinFIR offers two distinct modes of operation, each optimized for different workflows:

Loudspeaker Design Mode

This mode is dedicated to designing and optimizing multi-way loudspeaker systems. Key applications include:

• Crossover design with multiple filter types
• Individual driver frequency response correction
• Phase and time alignment between drivers
• Directivity pattern analysis and optimization
• Complete system integration and tuning

Room Calibration Mode

Focused on in-room acoustic measurements and correction:

• Multiple measurement position capture and averaging
• Automatic temporal alignment using GCC-PHAT algorithm
• Room response correction filter generation
• Spatially-averaged frequency response optimization
• Integration with existing room correction workflows

The mode is selected when creating a new project and remains fixed throughout the project’s lifetime. To switch modes, simply create a new project with the desired configuration.

Core Features

FIR Filter Design

LinFIR implements sophisticated FIR filtering with:

• Configurable filter length: From 32 to 65536 taps for precise frequency resolution
• Causality control: Continuous adjustment from pure linear-phase (0.0) to minimum-phase (1.0)
• Multiple filter types: Brickwall (Sinc), Linkwitz-Riley, Butterworth, and Bessel characteristics
• Kaiser window shaping: Fine-tune transition band characteristics

Frequency Response Correction

Advanced magnitude and phase correction capabilities:

• Target curve options: Flat response, Harman in-room curve, or custom user-defined targets
• Independent correction modes: Separate control for magnitude and phase correction
• Frequency range limiting: Apply corrections only where needed
• Maximum attenuation control: Prevent over-correction of deep nulls

IIR Filtering

Complement FIR filters with cascaded IIR sections:

• Parametric EQ: Precise peak/notch filters for resonance control
• Shelving filters: Low-shelf and high-shelf for tonal balance
• Crossover filters: Butterworth, Linkwitz-Riley, and Bessel topologies
• All-pass filters: Dedicated phase shaping without magnitude changes
• Auto-EQ: Automatic optimization to target curves with configurable parameters

Measurement System

Built-in exponential sine sweep measurement for impulse response capture:

• Configurable sweep parameters: Duration, amplitude, frequency range
• Quality validation: Automatic rejection of poor captures
• Microphone calibration: Import manufacturer calibration files for accurate measurements

Workflow Integration

LinFIR seamlessly integrates into professional audio workflows:

• Import/export WAV, txt, and specialized formats
• Direct export to Powersoft Armonia processors
• Export FIR coefficients in binary, text, WAV or CSV format
• Hypex FA Series amplifier configuration (HFD format)
• CamillaDSP filter export
• Comprehensive project management with auto-save

Platform Support

• Mac OS: Full feature support with low-latency audio
• Windows: Complete functionality with platform-specific audio optimizations
• Cross-platform projects: Projects are fully compatible across platforms