How to Set High-Pass and Low-Pass Frequency Filters on a Car Stereo Receiver
As an Amazon Associate, we earn from qualifying purchases made on our website. If you make a purchase through links from this website, we may get a small share of the sale from Amazon and other affiliate programs. You can read our complete affiliate disclosure/TOS for more details.

If you want to route certain frequency ranges to specific speakers connected directly to the head unit, some car audio stereo receivers have integrated and user-adjustable crossover filter that allows you to do so. These filters are high pass and low pass filters. Here is how they work:

High-pass Filters: High-pass filters are used to pass frequencies in the upper ranges and restrict low and mid frequencies. In a “two-way” crossover system, they work by restricting bass frequencies from mid-to high-range speakers.

Low-pass Filters: Low pass filters are used to pass frequencies in the low range while restricting higher frequencies. This means ow pass filter frequencies only reach the subwoofer.

(If you have a Pioneer stereo, please check out guide on how to setup HPF on your Pioneer stereo)

Why Adjust High and Low Pass Filters?

It is very important to properly adjust the high and low pass filters on your stereo. Firstly, correctly adjusting these filters will result in a much better sonic response.Why Adjust High and Low Pass Filters on car stereos

In addition, this will also promote speaker longevity by ensuring each speaker is operating in the correct frequency range.

How to Set High-Pass and Low-Pass Frequency Filters on a Car Stereo Receiver

Here are the exact steps you should follow to adjust the low-pass and high-pass filter settings properly:

1. Scan Your User Manuals for the Frequency Ranges

Examine your speaker-and-subwoofer owner manuals to find the right frequency response (Measured in Hz and kHz). Disregard this if the car doesn’t have after-market speakers installed.

2. Check the Frequency Slope Diagram

From the coaxial or high-range speaker’s owner manual, note the specific frequency in which the documentation shows a sharp decline for low frequencies. For your sub, focus on the reduction in the high-frequency slope.

3. Determine the Right Low-Pass and High-Pass Frequency Cutoffs

Choose LPF and HPF cutoff frequency points that provide “flat” transition between your low- and high-range speakers. To learn more, check our guide on subwoofer cutoff.

4. Determine the Appropriate Crossover Points

Consult your stereo receiver’s provided owner’s manual to determine the appropriate frequency crossover points.

As you do that, bear in mind that your car’s resonant frequencies, subwoofer enclosure, and the speakers’ mounting position will influence your final decision on this.

5. Make Adjustments to Your Frequency Settings

  1. Turn on your car’s stereo and go to the right crossover menu for the front high-pass filter.
  2. Choose the ideal frequency cutoff option.
  3. Repeat steps 1 and 2 for the rear speaker high-pass filter option.
  4. Adjust the LPF to have the same frequency as the HPF.
  5. Adjust the amp Gain to the lowest setting. Play music that features both low and high-frequency ranges, and then adjust the volume to the highest and most precise position.
  6. Adjust the sub’s crossover to the “Pass-Through” or “Off” position.
  7. After that, adjust the amp’s “Gain” to the loudest setting. Adjust the receiver’s volume to a normal listening level.
  8. Insert a sine-sweep test track CD and note any sound level differences.
  9. Listen and make minor adjustments to the low and high frequencies.

What Should I Set My HPF And LPF To?

Since you are protecting your sub from damage, you should set your HPF to a steep slope. Most people put it to 24b/octave.setting lpf on your head unit

To blend in with your mids, you should consider setting your LPF between 12 and 18db /octave.

 It’s important to remember that your sub will less likely creep into the neighboring frequencies when the slope is steeper (dB /octave).

How Do I Know if My Amp Gain is Too High

You should check the head unit’s volume control and your system’s setting. If you get the volume control to 50 and your system remains maxed at setting 20, your gains are most likely too high.

However, if you get it to 50, and the sound is not starting to distort yet, your amp gain is likely too low.

How Do I Match My Subwoofer Level to the Receiver Volume?

To match your sub-level to the receiver volume, you should turn up your receiver’s volume to the maximum. Ensure it is distortion-free. Move on and turn up the sub amp’s gain slowly until you start getting a balanced sound.

If that doesn’t sort you out, level control up and down a little to see whether the subs are combining their sound.

You can reverse your subwoofer’s speaker leads if your low frequency has high volume but lacks the much-desired punch. You reverse the subwoofer’s cone movements when you do this, which might be all you need to achieve your goal.

How Do I Troubleshoot Distortion From My Subwoofer

After following all the above tips, you can discover that some distortion is still coming from your subwoofers in some instances. If that’s what you are facing, you should use tried-and-tested tips to troubleshoot and fix this issue.

Here are the best steps that you should follow:

  1. Turn down the subwoofer’s gain.
  2. If you can’t get enough bass out of the sub at this point, get a more efficient amplifier combination.

Please note that you should never lower your full-range amp’s gain in an attempt to match the lack of subwoofer volume. If that’s what you’ve done, it could be the reason the amplifier is sending out distorted, clipped signals to your full-range speakers. It’s the easiest and one of the most common ways a few audiophiles unknowingly defeat their goal for a clean, full sound, which is the major reason they put in a sub.

Frequency Pass Filters and Distance

Our auditory system relies on high-frequency content for cues required to sort out proximity.

You can use a low-pass filter to sense whether a signal is further away from you than another (unfiltered) signal. So, it’s a technique you can use easily, especially if the signals are separated in the stereo field, to establish spatial contrast between them.

To get high-quality, you can use a low-pass filter on a delay’s output. As the delay component’s cutoff frequency is reduced, you should begin to hear a more realistic spatial separation between the delay and the direct signal.  

Please note that typical LPF cutoff frequencies range between 2 kHz to 5 kHz.

Once you’ve established LPF, you can introduce a high-pass filter as well. Use the tips we discussed above to introduce it. As you do this, please remember that cutoff frequency ranging between 100 Hz-250 Hz will likely exaggerate the spatial effect.

What Should I Set My Low Pass Filter To?

What should my low pass filter be set on my subwoofer? Low pass filters pass low frequencies to your subwoofers. Your low pass filter should be typically set to 80 Hz (12 db or 24 db Slope).

However, if you want to be more specific, a general rule is to set the Low-Pass Filter at a value approximately equal to (or below) 70% of your main speaker’s lowest frequency response. As an example, if your speaker’s frequency response goes down to 57Hz. 70% of 57Hz equals 39.9 or 40, so you should set the subwoofer’s low pass filter to 40Hz.

What Should I Set My Low Pass Filter To?

If you are working with a surround sound system, then your rear speakers will need a High-Pass Filter and two channels of amplification. The generally recommended settings are a HPF (5000 Hz) for the front tweeters, a HPF (80 Hz) for front midrange, a HPF (80 Hz) for rear speakers and 12 dB or 24dB slope.

Subwoofer Low Pass Filter On Or Off?

If you have a subwoofer in your home theater setup, then you should definitely turn on your low pass filter. Otherwise, you can get by with it off so that the main speakers will try their best to play bass as well.

Summing Up

Now you have all the essential steps and tips you require to set high-pass and low-pass frequency filters on your car’s receiver. You should be able to enjoy the robust fullness and beat of your music at any time. You can also tune up your subwoofer to match your system’s capabilities and your ear’s preference, which will help you have the best quality sound. So, all we would like to do at this point is to remind you to remember to be polite and reduce the booming volume whenever it might bother your loved ones, friends, or neighbors.