The fastest and simpliest way to add clarity to your vocals is to properly set your high-pass filter. The high pass filter will attenuate aspects of the vocal that are causing plosives or unwanted rumble and will help to make vocals sound cleaner.
High pass filters generally remove unwanted sounds that make your recordings muddy and naturally enhance the qualities of the lead instruments and vocals. However, the crossover frequency (frequency at which the high pass filter starts to filter audio) must be set correctly. As an example, if your crossover frequency is set to 120Hz, only frequencies above 120Hz will be allowed to pass through it.
Generally speaking, the best crossover frequency setting for your high pass filter is about 70Hz to 100Hz. However, you will need to test this for different singers to ensure that the high pass filter is not cutting out lower frequencies when the singer hits the lowest note in the song. If that is the case, adjust the cutoff frequency until you hear those mid-frequencies in the vocals.
The best procedure to follow when setting your high pass filter for vocals is to start with a low setting of about 70Hz and gradually adjust the frequency setting upwards until you start to hear it making the vocal sound thinner. This is normally up to 100Hz but can sometimes extend as high as 120Hz or even 200Hz. Keep in mind that once you hear it thinning out the vocals, you have gone too far. Dial back the frequency a little and keep the high pass filter at that frequency setting.
Read on to learn more about high pass filters and how to set them for better vocals.
What Is A High-Pass Filter?
The average human ear can perceive sounds with frequencies ranging from 20Hz to 20KHz. Sounds with frequencies lower than 20Hz or higher than 20KHz are usually not heard by us.
Sometimes, audio signals from amps or subwoofers fall outside the threshold of human hearing. Also, low frequencies can interfere with or damage your tweeters and high frequencies can do the same for your woofers. To prevent this, high- or low-pass filters are employed to keep the audio signals within the proper frequencies.
A high-pass filter (HPF) is a device that ha a setting that you will find on an amplifier and receiver. These devices allow high-frequency signals above a specific cutoff frequency to “pass.” Simultaneously, it attenuates low-frequency signals below the cutoff frequency.
In other words, an HPF removes low-frequency signals below a set cutoff frequency. This can help to improve vocals in an audio mix by removing the low-frequency rumbles that sometimes manage to creep in. Therefore, HPFs can give you cleaner vocals.
That’s the basic idea of what a high-pass filter does. Next, we will discuss how we can use it to clean up vocals.
The Best High-Pass Filter Settings for Vocals
What does a high-pass filter do to vocals? Well, it makes the vocals sound cleaner and less muddy. It also eliminates any low-frequency rumble or noise that makes its way into the audio signal.
Many consumer audio devices use fixed high-pass filters. These come in the form of a switch or button which you toggle on or off. Some have a fixed cutoff frequency —usually between 75Hz and 100Hz. However, others allow you to adjust the cutoff frequency.
Variable high-pass filters make it easier to choose a frequency. However, with fixed high-pass filters, you’re stuck with that cutoff frequency, no matter your preferences.
Many pro-level audio devices have adjustable or variable high-pass filters. These allow you to high-pass filter vocals with more control over the cutoff frequency. To use this type of HPF to improve vocals, follow these steps:
- Switch on the high-pass filter and play the audio containing the mix you want to filter.
- Start the high-pass filter at a low frequency (around 70Hz will do) and move it up gradually until you hear the vocals start thinning. This usually happens around the 120Hz to 200Hz range. Once the vocals start thinning, stop increasing the frequency. This means that you’ve gone too high on the frequency spectrum and you have to dial the frequency back.
- In this step, you’ll slowly return the frequency to the right level. To do this, slowly move the slider or dial down the frequency spectrum until you can remove the low frequencies without affecting the vocals. If you test this by bypassing and enabling the EQ, you should hear a much cleaner and clearer sound.
That’s it, how to adjust your high-pass filter to get the best vocals. Now, let’s find out the relationship between the capacitance and resistance of your audio device and the cutoff frequency, as well as how to manipulate it to get useful data.
Active High-Pass Filter Formula
There is a mathematical relationship between the capacitance and resistance of your speakers and the cutoff frequency. For a given cutoff frequency and resistance, you can calculate the capacitance value that will give you the predetermined cutoff value. The formula is as follows:
Where C is the capacitance, f is the cutoff frequency, and R is the resistance of the audio output source (the tweeter or subwoofer).
This formula has a variety of uses, depending on your scenario. For example, if you want to set a cutoff frequency for your tweeter, you don’t want to send low frequencies that can damage its drivers. Therefore, you can compute its resistance and capacitance to get the correct cutoff frequency.
With the formula above, you can calculate the capacitance, cutoff frequency, and resistance, provided the two other variables are available. For example: for a cutoff frequency of 5KHz, a tweeter with a resistance of 10Ω will need
If you don’t want to trouble yourself with the calculations, you can use an online active high-pass filter calculator. You only input the variables, and you receive your answer almost instantaneously. Most online high-pass filter calculators have sections for different types of high-pass filters.
Subwoofer High-Pass Filter Setting
Your Subwoofer HPF setting can make or break your audio experience. That’s why it’s crucial to know how to keep the HPF setting for your subwoofer at the correct level.
A subwoofer with a high-pass output of around 75Hz to 100Hz works for most music types. If you want to get your sweet spot manually, the steps to follow are quite similar to those for vocals.
To begin, start from a low frequency like 70Hz. Slowly increase the frequency until the audio becomes distorted. Then slowly return it to a lower level until you are satisfied. Keep in mind that extremely high frequencies can damage your subwoofer driver. So, keep the frequency within the limits of your device.
Now, you know how high-pass filters work, how they improve your audio experience, and protect your audio devices. With this guide, you should be able to tune your audio output to bring out the vocals the way you like it. Like using a microscope or smoothing a rough piece of wood, you need to get a rough setting first. Then, you fine-tune that setting until you reach your sweet spot.
Norvan Martin is the founder of BoomSpeaker.com. He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics.