High-pass and low-pass filters are crossover settings used in car audio systems to control which frequencies are sent to each speaker or subwoofer. They help ensure each speaker only plays the frequencies it is designed to handle, improving clarity, reducing distortion and helping protect the system.
A high-pass filter allows higher frequencies to pass through while reducing lower bass frequencies. This is commonly used for tweeters, midrange speakers and door speakers so they are not forced to play deep bass that may cause distortion or damage.
A low-pass filter does the opposite. It allows lower frequencies to pass through while reducing higher frequencies. This is most commonly used for subwoofers, helping them focus on bass instead of playing vocals, instruments or higher-frequency sounds.
Some systems may also use bandpass filters, which combine high-pass and low-pass filtering so a speaker only plays a specific frequency range. This can be useful for midrange or midbass speakers in more advanced setups.
A subsonic filter, also called an infrasonic filter, reduces extremely low frequencies that may waste amplifier power or cause unnecessary subwoofer movement. This can be especially useful in some ported subwoofer enclosure designs.
There is no single correct filter setting for every vehicle. The right crossover points depend on the speakers, subwoofer, amplifier, DSP, enclosure design, vehicle acoustics and listening goals. Incorrect settings can make a system sound harsh, muddy, weak or unbalanced.
For the best result, speak with your nearest Focal Authorised Australian Dealer. A professional dealer can set high-pass and low-pass filters correctly, tune the system and ensure your Focal speakers and subwoofer perform cleanly, safely and reliably.
