What Is Subsonic on Amp?

Hey there, friend!

Have you ever been confused by the label “Subsonic” on your amp? Don’t worry; you’re not alone. Many people are unsure of what to do when they see this term. That’s why we’ve created the ultimate guide to help clear up any confusion.

Let me tell you:

As someone who has spent years installing car audio systems, I know firsthand how important it is to understand subsonic filters. These filters control intensities and can make or break your system’s performance.

But here’s the thing:

Setting subsonic frequencies correctly can be tricky, and getting it wrong could lead to damage to your woofer or even your entire system. In this guide, we’ll cover everything from understanding subsonic filters to tuning them correctly for optimal performance. So sit back, relax, and let’s dive into the world of Subsonic!

Warning: After reading this guide, you may become a bit of an expert yourself!

Subsonic on Amp

Infrasonic or subsonic are sound waves below par at a certain frequency that can reach a human ear. Unlike a low pass filter, a subsonic or a high pass filter allows low frequencies to still pass through without causing distortion.

For example, you set your subsonic filter frequency to 30 Hz. When a sound wave of 20 Hz is produced, it will pass through but won’t be as high as before, and you won’t hear it to the same extent you did before.

But if you wish for a sealed enclosure, we recommend you set your high pass filter to 20 Hz or 25 Hz. This will not allow any sound below a certain hz threshold. So, the low notes that were a cause of frustration will no longer come out of your speakers.

The amplitude of those lower frequencies is brought down, you think, overpowers the high notes. But it does not destroy these waves. This is where a subsonic filter differentiates from a low pass filter that only attenuates signals that are above the limit you set for low frequency.

You can adjust this filter at different levels depending on the music you mostly listen to. A subsonic filter is not an on-off switch. Just consider you fixed the switch in the middle. Neither is it on nor is it off. This is exactly what a subsonic filter does with waves with frequencies lower than your set limit.

But while setting the limit of your high pass filter, you must also set the amp’s gain accordingly. Not doing so will damage your amplifier and subs, which is not something you want. So make sure to set everything at once and at the right limits.

Is a Subsonic Filter on Amp Necessary?

Many question why low bass is necessary when subwoofers’ purpose is the opposite. For an answer, you need to have an idea about the power handling of an amplifier/subwoofer. While working, the cone excursion of all speakers increases by a few points. But when does this increase?

Well, whenever your amplifier/subwoofer plays an octave lower, the excursion increases by a few factors, which is four. If you exclude a subsonic filter, the graph will represent waves that move significantly, but when below a certain level, the graph will drop.

So when you play a piece of music or any audio below 30 to 25 Hz, the waves may damage your audio system because of the stress it goes through. This is where the need for a subsonic filter, or in other words, the high pass filter, arrives.

When you use a high pass filter, the stress will decrease and will stop the waves from damaging your audio system. But not all systems require a subsonic filter; in that case, they don’t come with one. But it all comes down to the quality of your amplifier. So, before setting the subsonic filter limit, you must keep all aspects in mind.

To find the right tuning frequency, there is one thing we recommend you do. At the same time, play sine waves and bass sweep, and you will get your tuning frequency. You need to adjust the subsonic filter below this frequency.

Ideal Subsonic Filter Frequency

Although it varies from product to product, there is one general frequency you can set your subsonic filter at. Although, it is not necessary for your system to work the best at this frequency. You must test your tuning frequency for the best results and set the subsonic filter below.

But ideally, the best subsonic filter frequency is 35 Hz. This set frequency will allow you to listen to your music/audio best, and we assure you that you won’t even feel that the subsonic filter is on. This will save your system from any damage that comes its way and will also cancel any distortion.

Frequently Asked Questions (FAQs)

  • What should my subsonic be set on my amp?

For best results, you can set your subsonic frequency at 35 Hz. This will allow you to listen to your music in the same way. The only difference you will find is that there won’t be any distortion, and it will do no damage to your system.

  • What is the best Hz for a subwoofer?

The best Hz for a subwoofer depends on the tuning frequency, and we can only tell you the general frequency that is best for most speakers worldwide. However, this does not always mean it is the best for your subwoofer.

  • What is subsonic HPF on an amp?

The subsonic HPF on an amp is a component that reduces those low notes that become a cause of distortion and damage your amplifier/subwoofer. Always remember that a subsonic HPF is different from LPF.


A subsonic filter might not be a need in all situations, but it sure is when you want to save your system from damage. Setting this filter at the wrong frequency can also damage your system.

We made sure to explain the subsonic filter in depth. You can also find the general frequency at which you can set your subsonic filter. Lastly, it’s best to always check your tuning frequency for the best results.

Last Updated on March 16, 2023 by Danny Reid

Written by Danny Reid

Hey, I'm Danny, and I know how hard it can be to find the perfect audio gear. Need a new stereo, amp, speakers, or subs? Don't worry – my blog is here to help you cut through the noise! My mission is to give you the best reviews, so you can make the right decision for your audio needs. And if you ever get stuck thinking, "Where does this blue wire go?" don't worry – I've got tons of cool tips to help you out of any jam. So come along with me on this fun, sound-filled adventure, and let's find the perfect audio setup to make your tunes really sing!