What Is a High Pass and Low Pass Filter?

When setting up your speakers and subwoofer, understanding high-pass and low-pass filters is essential for getting clean, accurate bass, and avoiding overlap or gaps in your sound.

These filters control which frequencies go to which speakers, helping your system work together rather than fight against itself.

What is a Low-Pass Filter?

A low-pass filter (LPF) allows low frequencies to pass through to your subwoofer, while filtering out higher frequencies that the sub shouldn't play.

Most subwoofers, like all Arendal models, include a low-pass filter you can adjust directly on the sub itself or through your AV receiver or DSP.

Example:
If you set the sub’s low-pass filter to 80Hz, the subwoofer will start to gradually reduce output above 80Hz, depending on the filter’s slope (typically 12dB or 24dB per octave). It doesn’t completely cut off at that frequency. Think of it as the start of a fade-out.

What is a High-Pass Filter?

A high-pass filter (HPF) does the opposite: it allows higher frequencies through to your main speakers, while blocking lower frequencies.

This is especially useful in 2-channel or integrated amp setups where small speakers might struggle with deep bass. High-passing the speakers sends the low frequencies to the sub, allowing both to perform better.

Example:
This filter is commonly used in tweeters on crossover networks to ensure that only the high-frequency sounds are amplified and reproduced, while bass sounds are eliminated.

Where to Apply These Filters

• AV Receivers: Apply both high-pass and low-pass filters via bass management.
• 2-Channel Systems: May require a miniDSP or external crossover to apply proper high-pass filtering to speakers.

• Streamers with Sub Outputs: Most modern streamers with sub outputs apply both low-pass to the sub and high-pass to the main outputs, but it's best to check with the manufacturer or user manual to confirm.

   

Best Practices

• Set both high-pass and low-pass filters at the same crossover point (e.g., 80Hz) for a smooth handoff between speakers and sub.
• Avoid stacking filters unintentionally (e.g., using both the AVR and the subwoofer’s LPF simultaneously) unless you know how the combined slopes will affect the system.
• Use measurement tools like REW or Dirac if you want to fine-tune phase alignment and response.