LinFIR

A linear-phase crossover sums drivers without the phase rotation and group delay of classic IIR or passive crossovers, so the impulse and step response stay coherent.

FIR filters can correct magnitude and phase independently: flatten driver irregularities and excess group delay, or match a target curve, with limits and smoothing so the correction stays sensible.

Blend drivers with linear-phase versions of Linkwitz-Riley, Butterworth, and Bessel filters. Need asymmetric slopes? No problem. Want to apply a gentle low-pass to one woofer in a D’Appolito configuration? Easy.
Use this to:
• Compensate rising frequency response from high-efficiency drivers
• Tweak baffle step compensation
• Improve directivity by reducing frequency overlap

What you hear in a room is a mix of direct and reflected sound. That's why I design against the Directivity Index and the Predicted In-Room Response as well as the on-axis curve. Those curves say much more about how a speaker will sound in a real room.

LinFIR includes a minimum-phase conversion based on homomorphic filtering (Oppenheim et al., Signal Analysis by Homomorphic Prediction, IEEE TASSP, 1976), and a continuous causality control between linear and minimum phase.
This keeps the magnitude response intact while minimizing latency. It's useful for live sound, low-latency correction and hybrid designs.

LinFIR sends its filters directly over USB to the Hypex DSPs, FusionAmp amplifiers included, and exports them for CamillaDSP, MiniDSP, Q-SYS and Powersoft Armonía. Any other convolution engine can load the FIR filters as WAV, CSV, text or raw binary files. You set your DSP's sample rate and number of taps in the project, and LinFIR designs the filters within those limits.

A measurement microphone, its calibration file and an audio interface. LinFIR runs the sweeps and records them itself. If you already have measurements from REW, ARTA or another tool, you can import them as impulse responses (WAV or text) or as FRD files, which LinFIR converts to impulse responses.

Everything that works on the on-axis response: FIR and IIR crossovers, driver and room correction, time alignment, measurements and every export. The Advanced Module adds off-axis measurements and what is built on them, such as directivity, the spinorama and near-field splicing. It also unlocks the spectrogram and distortion windows and Hypex FusionAmp mode.

You choose. The lifetime license costs €149, tax included, paid once, and updates are free for all 1.x versions. The monthly license costs €14.99 a month after a 14-day free trial, and gives access to every version released while it is active. You can cancel it at any time, and the Advanced Module stays unlocked until the end of the month already paid. Either way, the Advanced Module runs on one computer at a time and you can move it to another one. If you haven't activated the key of a lifetime license, you can ask for a refund within 14 days of buying it.

Yes. LinFIR runs on Macs with Apple Silicon, on Windows through the Microsoft Store, and on Linux (x64 and ARM64) with .deb, .rpm and AppImage packages. A project saved on one system opens on the other two.

rePhase is free and many DIY builders know it. You build the correction band by band, much like with a parametric equalizer, for one driver at a time. LinFIR starts from the other end. You set the target curve, LinFIR calculates the filters of every driver within your DSP's limits (sample rate, number of taps), and you see the effect on the measurements and on their sum while you adjust. It also runs on Mac and Linux.

I do. I'm Arnaud Demion, an engineer with a PhD in physics, and I use LinFIR for the loudspeakers I design. Other designers use it too, and so does Amadeus. More about me.