How to Set Subsonic Filter? (Complete Solutions)

Are you looking for deeper, richer bass tones and a more immersive audio experience than ever before? If so, you want to learn about subsonic filters and how to set them to enhance your sound system performance.

When setting your subsonic filter, measure the tuning frequency of your subwoofer first. Depending on whether the enclosure is sealed or ported, set the subsonic filter to 25-35 Hz or around half the tuning frequency, respectively. Then set the bandwidth of the filter to about 24 dB for optimal filtration. Finally, adjust the volume of the audio to get the desired sound.

Ready to dive into the details? Let’s get started.

How to Set Subsonic Filter

What Does Subsonic Mean on An Amplifier?

Subsonic on an amplifier refers to frequencies below the lower limit of human hearing, which is about 20 Hz. These frequencies don’t contribute to the output of the amplifier and can cause distortion, so amplifiers usually filter them out using a low-pass filter.

Filtering out these frequencies helps maximize the efficiency of the amplifier, as it doesn’t need to waste power amplifying frequencies beyond what we can hear.

How Does a Subsonic Filter Work?

Subsonic filters are designed to eliminate any frequencies outside the range of human hearing. This means that any sounds lower than 20 Hz, which are too low for us to hear, will be reduced in intensity.

Subsonic filters work by dampening the amplitude of these low notes so that they don’t overwhelm the rest of the sound. This allows the higher frequencies to come through more clearly and helps reduce distortion and improve sound quality.

Subsonic filters are essential for anyone looking to get the best sound out of their audio system.

Why Use a Subsonic Filter?

Here are 4 crucial benefits of using a subsonic filter for your audio system:

  • First, subsonic filters reduce distortion from low frequencies, allowing for clearer sound and ensuring that the lower frequencies don’t overpower the higher ones.
  • Second, a subsonic filter helps reduce the strain on the system, preventing any electronic damage from occurring. This ultimately helps to prolong the life of your system and ensure that all components remain in good condition.
  • Third, subsonic filters can prevent your amplifier from wasting power trying to reproduce frequencies that you can’t hear anyway. This helps to conserve energy and ensure that the system is running optimally.
  • Finally, subsonic filters protect subs that are in ported enclosures. Without such a filter, the subs can easily lose all damping, becoming much harder to control and leading to over-extension and potential damage.

What Should I Set Subsonic Filter To?

When it comes to setting your subsonic filter for your subwoofer, it’s essential to strike a balance between power and accuracy.

For Sealed Enclosures

Aim for a subsonic filter around 25-35 Hz. Setting a filter at this frequency will eliminate the extremely low bass frequency from the sound input. This will prevent the subwoofer from expending a lot of energy and straining the limits of its excursion, leaving your subwoofer safe from potential damage.

For Ported Enclosures

To get the ideal subsonic filter frequency for ported enclosures, divide your tuned frequency by two and then divide again. For example, if your tuned frequency is 45 Hz, divide this by two to get 22.5. Then divide that number again to get 11.25. Subtract 11.25 from 45 and you have 33.75, which you can round up to 34 Hz. To ensure the subsonic filter is effective, you should also choose a steep slope such as 3rd or 4th Order (18 or 24dB/Oct).

Method For Subsonic Filter Setting

Setting a subsonic filter on a car audio system is relatively simple. Depending on the type of system you have, the steps may vary slightly. But here is an overview of the general process:

Step 1: Measure your subwoofer’s tuning frequency. You can use a test tone generator to generate a signal at a specific frequency or a digital multimeter to measure your subwoofer’s frequency response.

Step 2: Select the subsonic filter on your audio setup. Most audio setups come with a variety of equalizers, including a subsonic filter.

Step 3: Adjust the frequency of your subsonic filter to the appropriate setting. We’ve discussed previously what setting to use, depending on your tuning frequency and the kind of subwoofer enclosure you have. Use the digital multimeter to confirm the new set frequency.

Step 4: Set the bandwidth of your subsonic filter to about 24 dB on either side of your selected frequency. This allows for more room for the sound to be filtered.

Step 5: Adjust the volume of your audio system. Depending on the desired sound, the volume can be set to a lower level for milder music, or increased for a much deeper sound.

Step 6: Save the settings. Once you’ve set the subsonic filter to the desired level, make sure to save your settings to avoid having to adjust the settings anytime you turn on the audio.

Testing The Subsonic Filter Once Installed

Once the subsonic filter has been set, test the filter’s response by playing music through the system and checking to see if the filter is removing low-frequency noise and distortion.

You should check the gain of your amplifier and the SPL level at your listening position. Depending on your type of speaker, this may require adjustment. If the SPL level is too high, then you need to lower the subsonic filter.


Q: How Do You Know Where to Set Your Subsonic Filter on Your Car Amp?

To set the subsonic filter on your car amp, you should use a digital multimeter to measure the frequency output of the sound system. Connect the leads to the amplifier output and set the multimeter to measure frequency. Compare this measurement to the recommended tuning frequency range of your car amp and adjust the filter accordingly.

Q: How to Take Out the Subsonic Filter On An Amp?

To take out the subsonic filter on an amp, first, turn it off and unplug it from the wall to ensure safety. Then, locate the filter switch and unscrew it, which can be on the back or side of the amp. Replace the switch with a blank plate or a new filter switch and put back the screws. Finally, turn the amp back on and test out the sound.

Q: How do Make a Homemade Subsonic Filter for A Car Subwoofer System?

Using resistors, capacitors, and inductors, build a filter circuit that allows the lower frequencies to pass while attenuating the higher frequencies. Adjust the crossover frequency to the desired level by altering the capacitance and inductance of the components. Then connect the filter to the amplifier and the subwoofer in the audio signal chain, providing an additional layer of sound control adjustment.

Wrapping Up

In conclusion, setting a subsonic filter is a great way to improve the sound quality of your audio system and avoid damaging your speaker. A subsonic filter is a low-pass filter that blocks out frequencies below a certain point and should generally be set between 25 and 35 Hz.

To test the efficiency of the filter, you should run a frequency sweep and check the output. If you’ve done it right, you should be able to enjoy high-quality audio without damaging your speakers!