Subsonic Filter – A Detailed Guide
Audiophiles! All they love is deep and clear bass from their subwoofers. I’m one of them too. Sometimes, subwoofers start making rattling noises, resulting in an unpleasant experience.
However, there are some steps that you can follow to get to get rid of them and ensure a rich sound from the home theater or car audio system.
You must’ve heard of a device named as “Subsonic Filter” if I am not wrong. Setting the filter can be helpful in many different applications, including audio production, sound reinforcement, and acoustic instrument design.
Read the article below the end to learn about tips and tricks to use the subsonic filter to take your music experience to the next level!
What Is Subsonic Frequency?
A subsonic filter is an audio frequency filter that removes frequencies below the audible range or those lower than 20 Hz (subsonic filter frequency).
While subsonic filters are not always necessary for achieving excellent sound quality, they can help reduce unwanted rumble and noise, which helps create clearer-sounding recordings.
Subsonic filters also protect loudspeakers by blocking out low-frequency signals that could damage them. Some experts refer to subsonic filters as high-pass filters.
But that’s not actually true. While you can use both filters to remove unwanted low-frequency sounds from an audio signal, they are designed to operate at different frequency ranges.
As mentioned above, the primary goal of a subsonic filter is to eliminate specific frequencies from an audio signal before it’s amplified to prevent distortion caused by overloading the amplifier with too much bass energy.
In addition, these filters can provide additional benefits such as increased headroom and improved transient response when used correctly in conjunction with other components such as equalizers or compressors.
Do I Need a Subsonic Filter?
If the audio contains content that falls within the subsonic range (resulting in a distorted sound), then it can be beneficial to use one. However, there are some other factors that I consider before using such an option:
- Speaker type: A subsonic filter can help protect your subwoofer and speakers from damage caused by low-frequency sound waves. You should also use such a feature if your speakers or subwoofers are not designed to handle damaging frequencies to prevent them from blowing up.
- Audio type: If you listen to music that has a lot of low audio frequencies or sound effects, you may hear a rattling sound. Therefore, this feature will help you avoid such kinds of noise.
- Room acoustic: If you are using a powerful subwoofer in a small car or room, the bass will reflect by the acoustic, and as a result, you will hear a rattling sound. Therefore, you must use a subsonic filter in that case too.
Note: If you still need clarification about whether you should use a subsonic filter or not, I suggest you definitely use the one without any confusion. Because in the long run, you will be able to save your home or car audio system from any damage.
How to Set a Subsonic Filter?
This method can set lpf (Low Pass Filter) and subsonic filters together. You can also set LPF and HPF on head unit too. Anyway, follow the below steps for a successful setup:
1. Determine the Cutoff Frequency:
The cutoff frequency (I am discussing the cutoff point of the speaker, not the subsonic filter. A subsonic filter is not a cutoff.) is when your audio system or speaker begins to filter out sound.
It’s typically set somewhere between 20Hz and 50Hz, depending on what type of music you’re listening to and the characteristics of your audio system. To determine the cutoff frequency for your setup, you can read the user manual guide for the product you want to set for.
2. Access the Subsonic Filter Settings:
You may need a remote control, touchscreen interface, or physical buttons to access the subsonic filter settings. Depending on your audio system or amplifier, you may need to look for the equalizer menu and find a subsonic filter option.
Adjusting this setting can help remove the low-frequency rumble your speakers don’t pick up. Tweak it until you find the desired sound quality.
3. Adjust the Subsonic Filter Settings:
After getting access to subsonic filter settings, you’ll have to adjust the cutoff frequency to the desired value. Some systems may also allow you to adjust the filter slope’s steepness or the attenuation level applied to the filtered frequencies.
3.1 What Should My Subsonic Filter Be Set To?
Now, you’ll be wondering where to set your subwoofer filter at. So, here are my favorite and most valuable suggestions below:
3.1.1 For Sealed Enclosure:
For me, a sealed enclosure’s ideal subsonic filter setting is 20-30 Hz. This frequency range will help prevent any power from reaching the subwoofer, minimizing distortion and preventing over-excursion of the woofer.
Setting the filter too low can cause bass cancellation and reduce sound clarity. Selecting it too high can allow unwanted frequencies to pass, causing increased distortion and poor good quality.
3.1.2 For Ported Enclosure:
The subsonic filter should generally be set to around 20-25 Hz for a ported enclosure, allowing all bass frequencies below a certain hz threshold to be filtered out, thus protecting the speaker from overexertion and ensuring no low frequencies are lost in translation. In addition, a higher subsonic filter can help reduce port noise and make your music sound more precise and crisp.
About Octave & Safety:
Setting the subsonic to 1/2 an octave below our tuned frequency is a safety measure that helps filter out any music or sound waves below the given port’s frequency.
The mathematics behind this concept is pretty straightforward when understanding octaves – one octave lower equates to half of a particular frequency in terms of number value.
In comparison, one octave higher signals double the original number value. To illustrate an example, if we have a tuned frequency of 45Hz, then one lower octave would equal 22.5 Hz, and half an octave would result in 11.25 Hz (rounded up for accurate filtration).
The result is setting your sub-sonic to 34 hz – this way, you get maximum protection against low frequency that could potentially harm or damage your woofers without affecting your desired audio output. (You must give yourself a while to learn the right tuning frequency.)
Subsonic Filter Vs. Low Pass Filter:
I’ve shared the table demonstration below for your better understanding:
| Property | Subsonic Filter | Low-Pass Filter |
|---|---|---|
| Frequency Range | Below the Tuning Frequency | Above the Cutoff Frequency |
| Purpose | Protect subwoofer from damage due to over-excursion | Filter out high-frequency sounds |
| Crossover Slope | Typically 12 dB/octave or steeper | Typically 6 dB/octave to 24 dB/octave |
| Application | Used with ported or sealed enclosures | Used in crossover networks to direct high-frequency sounds to tweeters or midrange drivers |
| Setting | Typically set to half an octave below the tuning frequency | Set based on the desired frequency range for the driver or speaker |
How to Set Subsonic Filter on Amp?
You can only set the subsonic filter on the amp in some setups. Here’s how you do it:
- Locate the filter control: Check the amplifier from all sides. It may be a physical button or knob on the amplifier. In modern amps, you can access it through a menu on a digital display.
- Determine the recommended cutoff frequency: As mentioned above, every subwoofer or speaker has a different cutoff frequency. You can check it on the user manual guide. Otherwise, set the frequency range at different levels and check where you eliminate the noise.
- Adjust the subsonic filter cutoff frequency: Once found, you should save the setting somewhere you can quickly determine again. Keep the frequency level on that spot using knobs or touch screens.
- Test and adjust as needed: You should give time while testing your subsonic range. You can play music with a lot of bass and listen for distortion or noise. Adjust the cutoff frequency as needed to achieve the desired sound quality.
Difference While Subsonic Filter On or Off:
Now, let me tell you about the difference! When you turn off a subsonic filter, all frequencies, including extremely low-frequency sounds below the human hearing hz threshold, can pass through to the subwoofer, causing the subwoofer to work harder than it needs to and may lead to over-excursion of the subwoofer at specific frequencies, resulting in distortion or even damage/failure of the device.
When a subsonic filter is switched on instead, it filters out any very low-frequency sounds below its set tuning frequency for that particular enclosure; this prevents overstraining and protects your expensive amplifier from being driven too hard at these lower settings.
In most home setup scenarios, however — unless you have an empathetic ear — differences between turning a subsonic filter on or off will likely not be noticeable by just listening alone; therefore, such alterations don’t have much impact when applied outside of the high-performance home or car audio systems where improved fidelity and reduced distortion need more intense levels of control over signal output. (Knowing certain hz threshold is essential)
General FAQs
Is Subsonic Filter the Same as High Pass Filter?
No, a subsonic filter and a high pass filter are different. A subsonic filter is designed to reduce frequencies below a certain point called the cutoff frequency, whereas a high-pass filter will block out lower frequencies and allow higher ones to pass through. Therefore, they both serve different functions.
Should I Use a Subsonic Filter on a Sealed Box?
Yes, you can use it on a sealed box. It helps to limit the number of low frequencies passing through the enclosure while preserving overall sound quality. This filter prevents problems caused by over-excursing the woofer in bass-heavy music.
What Is Subsonic Frequency?
The subsonic filter frequency is sound energy below the range of human hearing, typically less than 20 Hz. You can use it for products such as vibration therapy and sleep aids that don’t disturb others in the same room. Subsonic frequencies also have applications in entertainment, communications, and industrial processes.