- FIR Filtering – Analog Passive Crossover Phase Linearization VS Active Linear Phase CrossoverFor this first blog post we wanted to dive into a subject that’s been barely democratized and is very contemporary in large PA sound systems: FIR filters Quick introduction, FIR stands for “Finite Impulse Response”. It represents an advance in digital audio possibilities that’s seen its use rise in the… Read more: FIR Filtering – Analog Passive Crossover Phase Linearization VS Active Linear Phase Crossover