How to Set High-Pass and Low-Pass Frequency Filters in Car Audio [EXPLAINED]

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Car Audio High-Pass and Low-Pass Frequency Filters settings

70 to 80Hz is a general rule for a car stereo sub-low pass filter (LPF) setting. After you’ve set it, slowly fine-tune and listen to find the best sound. For high-pass frequency filters (HPF), manufacturers frequently include specifications indicating the best cutoff frequency to use. Often, it is explicitly stated as the preferred cutoff, while on other occasions, you’ll have to rely on frequency response info from a speaker.

Step-by-Step Instructions for Setting High-Pass Frequency Filters (HPF)

Here are the steps you need to follow to set high-pass frequency filters.

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Step 1: Refer to the Speaker Manufacturer’s Recommendations

Manufacturers frequently include specifications indicating the best cutoff frequency to use. Often, it is explicitly stated as the preferred cutoff, while on other occasions, you’ll have to rely on frequency response info from a speaker.

If neither is provided, the tables below can be used. The good news is that there is generally some information available to tell you the frequency response range of a speaker, which you can use to set the high-pass filter.

Step 2: Refer To Car Audio High Pass Crossover Frequency Table

During bass-heavy music and particularly under high power, car audio systems are prone to poor sound, warping, and “bottoming out.” However, this can be avoided somewhat by using the recommendations in the car audio high pass crossover frequency table.

Speaker type/system Crossover frequency
Front or rear full-range coaxial or component speakers 56, 60, to 80 Hz high pass
Subwoofer subsonic filter 20-30Hz high pass.
Tweeters 3-3.5kHz high pass
3-way speaker systems 3.5kHz (mid/treble) & 500Hz (mid/woofer)
2-way speaker systems 3kHz to 3.5KHz to tweeters
Midrange or woofer speakers 250-500Hz high pass 

Step 3: Set the Crossover Slope for High-Pass Filter

The slope is the degree to which a crossover’s filtering capacity is steep. In other words, it measures how effective it is at preventing sound from passing through the crossover’s cutoff point.

Slopes are measured in decibels (dB) per octave, which is written as “dB/octave.”

In general, a -12dB slope is often the best option and works well with most sound systems. To block bass from reaching tweeters or small speakers, I suggest at least a 12dB slope, or preferably an 18dB slope if you have the option.

Step-by-Step Instructions for Setting Low-Pass Frequency Filters (LPF)

Here are the steps you need to follow to set low-pass frequency filters.

Step 1: Start by Setting Low-Pass Filter to 70 to 80Hz

70 to 80Hz is a general rule for a car stereo sub-low pass filter (LPF) setting. After you’ve set it, slowly fine-tune and listen to find the best sound.

Ideally, you should only hear pure, smooth bass from the subwoofer and no gaps in the audio signal when listening to music or watching a movie. If the level appears to be too low, you may need to enhance the gain on a powered subwoofer.

Step 2: Refer To Car Audio Low Pass Crossover Frequency Table

You can refer to the table below when looking to set low-pass frequency filters for different woofer types.

Woofer type Cutoff frequency
Powered or amp-driven subwoofers 70 to 80Hz
Woofers/midbass in a 2-way speaker Depending on the design and speakers, the frequency range can range from 1.5 to 3.5 kHz. 
Midbass woofers in a 3-way system 250Hz

Step 3: Set the Crossover Slope for Low-Pass Filter

In general, a -12dB crossover slope is often the best option and works well with most sound systems. A sub with a slope of 12dB or 18dB generally sounds great.

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