What Is LPF On Amp: 3 Quick Information & Application

Music and sound technology can be confusing, especially when it comes to the complex settings and jargon used. One such term that might have left you scratching your head is “LPF.”

But what is LPF on the amp? How does it affect your audio experience, and how can you use it to your advantage? In this article, we’ll dive deep to provide comprehensive insights to help you grasp this concept clearly.

What is LPF on Amp?

LPF, or Low Pass Filter, is a setting found on your audio amplifiers, that works like a door and only allows certain sounds through. In detail, it will let through sounds with low frequencies, while blocking sounds with high frequencies. So, the LPF helps you control and balance how much high-pitched and low-pitched sound you hear.

For instance, if you set the LPF for your subwoofers at 160 Hz, any sounds above that frequency will be filtered out, and only frequencies below that frequency will be sent through the subs.

Car audio amplifiers

What is HPF on Amp?

The HPF, or High Pass Filter, only allows the high notes (high frequencies) in while keeping the low ones (low frequencies) out. That’s why it’s called a “high pass” filter – it lets high frequencies “pass” through.

For example, when you’re playing a song on your electric guitar through an amplifier with an HPF setting. If you turn up the HPF, the deep, bassy notes might start to sound quieter, while the high-pitched notes could sound louder and clearer.

Additionally, some speakers (like tweeters) are designed to play high notes and can be damaged by low frequencies. So, using an HPF can help protect them by making sure they only get the high notes.

Car tweeter

Common Settings on Your Amp

Your amplifier comes equipped with a variety of settings to fine-tune your audio experience. Here are some settings you’ll likely encounter and how to apply the LPF:


Distortion is the sound we see in electric guitars and amplifiers. It changes the clean, clear notes that an instrument produces into something grittier and harsher.

 For instance, when your guitar is distorted, it means that its waves have been “clipped” or squashed, which leads to a more growly sound. You can control the level of distortion on your amp, allowing you to add as little or as much of this energy as you like. Normally, in music genres like rock, metal, or blues, distortion is frequently used to give the music its characteristic “heavy” sound.

Furthermore, in-car audio, an LPF applied to a distorted signal can remove unnecessary high-frequency components. In detail, if you’re listening to heavy metal music and your car’s audio is distorted when the car audio is on, the music can sometimes get uncomfortably shrill. By setting an LPF, you can remove the harsh frequencies, providing a more comfortable listening experience while preserving the crisp character of the music.


“Reverb” is just a shorter way of saying “reverberation”, but you might know it better as an “echo”.

On an amp, the reverb setting simulates this echoing effect. It makes your music sound as though it’s being played in a large, open space. It’s like singing in the shower and hearing your voice bounce off the walls – that’s reverb!

If you don’t want to hear this sound too much, an LPF can prevent the echo effect from becoming too overpowering. Normally, too much high-frequency reverb in a small space like a car can make the audio sound unnaturally bright or harsh. An LPF helps maintain the spaciousness imparted by the reverb but without the harshness of the high frequencies.


The chorus takes your original sound, clones it a few times, and then tweaks each copy just a little bit by changing its pitch and timing slightly. As a result, your single instrument now sounds like several are playing at once.

For example, if you’re a guitarist, using the chorus effect can make it sound like two or three guitars playing the same notes, but not perfectly in sync. This results in a thicker, fuller sound that can add a lot of richness to your playing.

Additionally, the Chorus can often sound muddy in-car audio systems because the effect itself tends to increase the richness and fullness of the sound. If there are too many high-frequency sounds, the effect can get lost. Using an LPF can help maintain the clarity of the chorus effect, ensuring your audio sounds lush but clear.

Car audio stereo


Lastly, gain might seem complicated, but it’s quite simple – it’s all about loudness. When you turn up the gain on your amp, you’re making the sound from your instrument louder before it reaches the amp’s other controls, like volume or EQ.

But be careful, too much gain and your sound can become distorted, which can be particularly harsh to the ears. To solve this problem, you can use an LPF, allowing low frequencies. Thus, you can enjoy loud music in your car without the harshness associated with high gain levels.

What is the “Slope”

In LPF and HPF settings, you’ll often hear the term “slope”. The slope is simply a measure of how quickly the filter reduces the signal’s strength beyond the cutoff frequency. It’s typically measured in decibels per octave (dB/octave). A steeper slope results in a more abrupt cut-off, while a gentler slope allows for a more gradual fade-out of frequencies.

In a car audio system, you might have different speakers that are specialized for different types of sounds. For instance, you might have subwoofers for deep, low-frequency sounds, tweeters for high-frequency sounds, and mid-range speakers for everything in between.

Let’s say you’re setting up an LPF for your subwoofers, and you’ve set the cutoff frequency at 100 Hz. Now you need to decide on the slope.

Suppose you choose a steep slope of 24 dB per octave. This means that for every octave (or doubling of frequency) above 100 Hz, the volume is reduced by 24 dB, which is a significant decrease. So, frequencies at 200 Hz will be much quieter, and by the time you get to 400 Hz, they’ll be barely audible. This steep slope ensures your subwoofers only play those deep, powerful bass notes, and none of the higher frequencies.

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Understanding the ins and outs of your amplifier settings, including “what does LPF mean,” can greatly enhance your audio experience. By mastering LPF, HPF, and the associated terms, you can manipulate the frequencies in your audio to suit your preferences and create the perfect sound.

Remember, these settings are tools at your disposal, so don’t hesitate to experiment and tune your audio just the way you want it!


  1. What's the ideal setting for my LPF?

    When it comes to fine-tuning your LPF, a good starting point is to set it at 50 Hz. This means that any sound waves below 50 Hz will get channeled to your subwoofer. In contrast, frequencies at 100 Hz (which is an octave above your setting) are dialed down to be practically inaudible.

  2. Should I choose LPF or HPF on my Amp?

    When determining whether to choose LPF or HPF on your amp, it largely depends on the type of speaker you're dealing with. If you're working with subwoofers, the low-pass filter (LPF) is the way to go. Conversely, if your system comprises speakers designed to take on the higher frequency ranges (or you have a separate subwoofer handling the lows), then the high-pass filter (HPF) would be the optimal choice.

  3. How do I set the LPF for my subs?

    When it comes to setting the LPF for your subs, a good rule of thumb is to aim for a value that's roughly 70% of your primary speaker's lowest frequency response. For instance, if your speaker's frequency response reaches down to 43Hz, you'd calculate 70% of 43Hz (which is about 30Hz) and set your subwoofer's LPF to that. This allows your subwoofer to effectively handle those low frequencies, giving you the deep, resonant bass that's so important for a well-rounded sound.