Table of Contents
What is EQ?
EQ, which is short for equalization, is the manipulation of levels over the audio frequency spectrum. Frequency is essentially the rate at which an audio signal vibrates per second and can be measured in Hertz (Hz). The higher the frequency, the faster the audio signal is vibrating. The audible frequency range is from 20 to 20,000 Hz, this is the frequency range we are concerned with when we EQ.
In music, an Audio Engineer may have the responsibility of “mixing the track”. This means that they have to increase and decrease the levels of certain frequencies for a range of instruments to best allow instruments to be heard clearly through EQ. This process is subjective and different Audio Engineers may choose to EQ differently to others, whether it is because they believe a different technique sounds better than that of another engineer, or to achieve a different style of mixing.
An Audio Engineer may also be responsible for applying EQ to podcasts, of which there is a range of reasons why EQ should be applied to the speech recordings on podcasts, which will be discussed within this article.
What are the Best EQ Settings?
There is not a “best” or default EQ setting that can be applied to achieve high-quality speech. One reason for this is because everyone’s speech varies; the frequency range and the amplification and attenuation of frequencies vary for all people.
The human voice has a resonant or fundamental frequency, simply put, this is the natural frequency used from the voice box when talking. The table below shows the variation that could occur depending on the type of speech.
|Demographic||Resonant Frequency (Average)|
|Child||250 Hz to 400 Hz|
|Adult Female||200 Hz|
|Adult Male||125 Hz|
It can be made clear from this table that applying a single EQ setting to all speech types will be ineffective. To find out more, check out the source of this table and the reason the resonant frequency varies between different people in the following short video.
The room the speech recording takes place should also be considered. Some rooms are more reverberant than others, meaning that some frequencies can be more prevalent compared to a less reverberant room, so the EQ setting cannot be carried over between rooms.
Within some poorly treated rooms, there’s also the issue of room nodes. Although more of an issue when recording music compared to speech, they may still cause issues in very reverberant spaces. Room nodes are where a sound source can be amplified and attenuated at different areas of a room. Again, this is of little concern to speech and only has some relevance to the topic discussed in this article, but still might be of interest. You can learn more about room nodes here: https://en.wikipedia.org/wiki/Room_modes
Before moving on, let’s clarify some common important EQ terminology:
- Removes all frequencies above a set frequency
- Removes all frequencies below a set frequency
- Attenuates all frequencies below a set frequency
- Attenuates all frequencies above a set frequency
- Increase frequencies at a set frequency
- Decrease frequencies at a set frequency
Types of EQ
There are multiple types of methods for applying EQ in your DAW. The following examples have been ranked from least to the most complex. Each has its own pros and cons within the context of manipulating the frequencies of speech.
Low-pass and High-pass Filter: This EQ type allows you to easily cut off the high and low-end sounds of the frequency spectrum.
Graphic EQ: This EQ type allows a user to individually increase and decrease the levels of a range of frequencies.
Parametric EQ: The Parametric EQ allows for manipulation of the frequency, filter type, Q factor, and gain. To see a summary of these terms, take a look at the table below. This filter allows the gain manipulation of multiple frequency bands.
|Filter Type||This allows the manipulation of a range of filter types, which includes low-pass, high-pass, low-shelf, high-shelf, peak, and notch|
|Q Factor||This indicates the bandwidth around the frequency that the EQ is applied to. A high Q Factor results in the gain increase or decrease being applied to a lower bandwidth section; it creates a harsher result. A low Q Factor results in the gain increase or decrease being applied to a high bandwidth section; it creates a softer result.|
|Gain||This is the amount the level is increased or decreased in dB.|
Semi-parametric EQ: This is the same as a Parametric EQ, just without the ability to adjust the Q factor.
|Low-pass and High-pass Filter||Simply and effectively allows the high and low ends to be removed||Limited application for EQing speech|
|Graphic EQ||Allows gain manipulation of a range of frequencies and can be used to recreate different filter types||Can require careful and delicate listening to be effective. Some frequencies are left out meaning it can be difficult to recreate a wide notch or peak|
|Parametric EQ||Allows the easy manipulation of a range of filter types and high control over frequencies. Allows the visualization of the manipulation.||Can be overwhelming to first-time users|
|Semi-parametric EQ||Allows a simplified version of the Parametric EQ that may be easier to use for EQ newcomers in comparison||Misses out on the Q Factor that can be manipulated using the Parametric EQ|
Why Should You EQ?
You should EQ to improve the quality of your audio signal and increase clarity. As previously discussed, you should do your best to compensate for the effects of the room you’re recording in.
Increased clarity can increase speech intelligibility and can make your podcast come across as more professional. If the quality of your podcast does not match that of other podcasts people listen to, your podcast will be perceived as having lower production values than other podcasts.
When Should You EQ?
EQ can be one of the most important features when in the post-production stage of your podcast. It will be most apparent that you need to EQ when you find yourself struggling to hear the speech clearly. This could be caused by a range of issues, including the proximity effect.
The proximity effect is essentially where the bass level increases due to the close proximity of a sound source to a microphone. One speaker may have been closer to the microphone than the other and so the bass levels may need to be reduced using EQ.
Alternatively, use some reference material for comparison. I’d recommend the Joe Rogan Experience and Lex Fridman Podcast, both of which can be found on YouTube, for reminding yourself what some high production podcasts sound like.
This is especially important to do when you find you have been listening to your podcast for a long time during the editing stage. Even when you think you’ve achieved the best EQ settings possible; it can be easy to forget how some of the best podcasts sound and this should inspire you to refine your EQ further.
Recommendations on How to EQ
You could start off with finding the frequency response of your microphone. This can give you a general idea of the EQ that is naturally applied by the frequency response of your microphone, meaning you know where some areas of high-frequency response may be an issue and should be manipulated during the post-production stage.
You can learn more about frequency response, learn how your microphone colors the audio signal of speech, and how to measure the frequency response of your microphone on one of our previous articles: https://www.theseasonedpodcaster.com/how-to-guides/how-to-test-microphone-frequency-response/
I’d recommend you use a Parametric EQ to apply and test the following recommendations. This will allow the most control to achieve what is stated below.
The first thing you should do when applying EQ to a podcast is to remove the low frequencies. Anything below 80 Hz is unnecessary content and barely audible in human speech. For this, I’d recommend you apply a high-pass filter at 80 Hz. I would recommend smoothing the cut-off to be more natural sounding compared to a harsh cut.
Reducing the frequencies here will also reduce noises such as table tapping and other vibrations which are easily picked up at low frequencies. Not reducing the levels here can create a muddy effect on the sound.
As discussed, you are likely to find a resonant frequency of around 125 Hz to 200 Hz for adults. Attenuating these frequencies can result in the sound becoming weak or thin. Increasing them can have the undesirable effect of making a voice boomier. You probably wouldn’t need to increase the gain here in a room that is already quite reverberant, although you may be missing out on some areas of warmth and vocal fullness if you don’t have the level high enough.
Frequencies between 400 Hz and 1 kHz can be reduced to remove some slightly unnecessary speech content. It is important to finely reduce these levels here, if required, to achieve a clearer voice. Decreasing the levels too much can make the signal sound hollower. Increasing the gain too much here can make your recorded speech sound more nasal, which can be distracting.
The 2 kHz to 4 kHz frequency range is arguably the most important range to EQ as this is where our ears have a natural ability to focus on this area of the frequency spectrum. Increasing the gain of frequencies here can add a significant amount of clarity to the human voice. This is where more presence can be achieved, although, increasing the gain too much here can create sibilant sounds. Simply put, sibilant sounds feature ‘s’ sounds; they sound harsh and can really put you off listening to a podcast.
Sibilant sounds are most prominent up to around 12 kHz, so you could in theory increase the levels between 2 kHz and 4 kHz to achieve more clarity in the speech and also attenuate the frequencies between 4 kHz and 8 kHz to remove any sibilance that occurs. Alternatively, a de-esser is a tool likely built-in to your DAW that can automatically reduce the sibilant sounds for you and without you having to waste time trying to EQ-out the sibilance.
A high gain for frequencies above 12 kHz can add openness and air to the speech. Having these frequencies too low can often dull the sound, however, performing frequency analysis on some professional podcasts shows that some audio engineers do not care for some of the higher frequencies and simply low-pass them off.
The Joe Rogan Experience is a podcast that has high frequencies significantly attenuated. This could have been done due to the distortion that occurs at high-frequencies when publishing content on the internet with a low bit-depth. Distortion occurs because there is not enough data available to store a higher-quality audio signal.
It is understandable that some audio engineers would rather not take the risk of a user getting access to a lower-quality version of the podcast, such as is sometimes done with streaming platforms to reduce the amount of internet data a user requires to listen, if it means they’ll hear a distorted podcast.
Applying EQ can be a time-consuming process, don’t be afraid to learn from others to get an understanding of where to start and keep listening carefully while applying EQ to know what works best for your set up. This will undoubtedly improve the quality of your podcast. Here is an example of an EQ preset I made that I used for a podcast I used to work on. After applying this setting, I’d carefully listen and alter the gain until I could improve it no more. Hopefully, after following this tutorial, your vocal EQ will look something like this.