Crossover filters are constructed using combinations of inductors and capacitors. Inductors resist changes in current and block high frequencies while allowing low frequencies to pass, making them suitable for low-pass filters that send bass frequencies to woofers. Capacitors resist changes in voltage and block low frequencies while allowing high frequencies to pass, making them suitable for high-pass filters that direct treble frequencies to tweeters. Midrange drivers typically require band-pass filters, which combine high-pass and low-pass filters to isolate mid frequencies. The design and value of these components dictate the exact crossover frequency and slope, so precise calculations and tuning are needed to achieve the best sound.
Phase and time alignment are important considerations when designing or selecting a crossover. Because the filters introduce phase shifts — delays in speaker crossover explained certain frequencies relative to others — misalignment can lead to cancellation or reinforcement of certain frequency bands where driver outputs overlap. This can cause uneven frequency response, dips, or peaks in the sound. Proper crossover design and sometimes physical alignment of drivers within the speaker enclosure help minimize these phase issues, ensuring smooth transitions between drivers and a more natural sound.
Crossover design also impacts the overall efficiency and power handling of the speaker system. Since passive crossovers operate after amplification, power loss occurs in the filtering components, which can reduce the efficiency of the system and generate heat in the coils and resistors. The quality and rating of these components affect durability and sound quality, as low-quality parts may distort or degrade over time. Active crossovers avoid this issue by splitting frequencies before amplification, improving power efficiency and allowing for more precise control over driver output levels and frequency response.
Many speaker manufacturers design crossovers specifically tuned to the drivers used in their systems. This tailored approach ensures that the crossover complements the unique frequency response, impedance characteristics, and physical placement of the drivers, providing the best possible sound. Audiophiles and sound engineers sometimes modify or build their own crossovers to customize sound profiles or adapt speakers to particular rooms or listening preferences. Modern software tools can simulate crossover designs, making it easier to predict performance before physical implementation.