Are you a Blind user trying to get familiar with EQ in Apple’s Logic Pro? This tutorial from a screen reader perspective will introduce you to the Channel EQ and its parameters. After an overview of the interface and a brief explanation of the parameters, we’ll get into some audio examples of what they do all while using speech.
To see how to add the Logic Channel EQ to a track, see Instantiating A Plug-in: How to Add An Effect to a Track in Logic Pro Using VoiceOver.
The audible hearing range, generally speaking, goes from 20 hertz ( written as 20Hz) to 20 kilohertz (written as 20KHz) which is also 20,000 hertz. 20Hz is the extreme low end and 20KHz is the extreme high end. Unless you have bionic hearing, you probably won’t be able to hear much below 40Hz or even 50Hz on the low end but will likely perceive or feel frequencies down to about 20Hz. On the High side above 16KHz (16000Hz)is where the average hearing may start to taper off, with our perception filling in for us going up to about 20KHz.
An EQ in its basic of terms is a volume control for any given frequency. An EQ like the channel EQ which ships with Logic is a Parametric EQ. This means that it allows you to set the exact frequency value (anywhere from 20Hz to 20KHz ), set the Gain (how much you want to boost or cut that frequency – positive values boost the frequency and negative values cut it), and the Q which sets how wide the boost or cut is. Wide as in how the frequencies around are affected.
So let’s say you set the frequency to 100 Hz, and pull down the gain to -3dB, you will be cutting that frequency by 3dB. Now where you set the q will dictate if you are only affecting 100Hz (which will be a narrow Q – some 3rd party EQ’s may refer to an extremely narrow Q like this as a notch) or if you start to affect the frequencies around 100HZ to some extent, like say 90Hz to 110Hz. The wider the q The more frequencies on either side of the selected frequency value that gets affected to some extent. However this effect isn’t linear. Say you cut 100Hz by 3db, you may only be cutting other frequencies by 1dB or 2dB. The further out they are the less they are affected.
To generalize this further, 20Hz to 200Hz give or take is considered the low end. 200Hz to about 5KHz (or 5000Hz) is considered the mid range area and 5KHz (5000Hz) to 20KHz (20,000Hz) is considered the high end.
Things like guitar amps or stereos etc. that have EQ on them usually have low, mid and high controls. In this case the designer preset the frequency , and q for the EQ, and the knob you as a user is provided with is just the gain knob to cut or boost those frequencies. Consult your favorite manual to learn where they set the frequency and q as this will vary from device to device.
A Low cut or high pass as it’s also known (different EQ’s use one or the other title for this filter)) does just that; cut the lows or allow only the highs to pass through. So unlike a peak EQ band, if you set the low cut filter to 100Hz this pulls down 100 Hz and everything below 100Hz as well. This means only the frequencies above 100Hz is allowed to pass through for the most part. The amount by which everything will be turned down is determined by the slope. At 12dB per octave for example, 100Hz and below is reduced by 12dB. 50Hz and below will be reduced or attenuated by 24dB; and 25Hz would be attenuated by 36dB.
This is useful for say a guitar amp, since not a lot of info resides in the low end for a guitar and turning down some of that stuff below 100Hz allows for the frequencies above 100Hz to be heard better but allows for more space for the bass and kick drums to be heard. In the tutorial I demonstrate this on a voice. You may want to listen intently on headphones at first while learning this stuff to hear what can seem subtle at first, but you should start to hear more of the Piano’s low end once the low cut filter is set on the voice.
The opposite of these filters are the high cut or low pass which cuts the highs or only allows the lows to pass through. Much like the Low cut filter, the Hi cut filter’s slope will adjust how much frequencies above the selected frequency is reduced or attenuated. In both the case of the low cut and high cut you will want to set the slope to something between 12dB to 24dB per octave, and then sweep around the frequencies to find where they sound best. The Q in the case of the filters are useful to boost at the cut off frequency to compensate for some of the loss of low end/High end that the filter can bring. See the tutorial to hear this in action. Once again headphones may help if you are new to this.
Much like filters, the Logic Channel EQ also has a Low Shelf and a High Shelf. Unlike the filters however, a shelf allows you to boost or attenuate at the selected frequency and below or above it respectively. Also unlike filters there isn’t a slope and it’s boosted or reduced by the same amount. Using our example of 100Hz again, a low shelf set to 100Hz means you can boost or attenuate everything around 100Hz and below it by whatever you set the Gain to. So if the gain is at -3db, you are reducing 100Hz and below it by 3dB. If the gain is at 6dB, then you are boosting 100Hz and below it by 6dB.
The same can be said for the High shelf. If you have a High shelf at 10KHz, you are boosting or reducing around 10KHz and frequencies above it by the amount you have the gain set to. Once again for an example, if the gain is at -3db, you are reducing 10KHz and above it by 3dB. If the gain is at 6dB, then you are boosting 10KHz and above it by 6dB. The Q for the shelves work similarly to how they work for the filters.
Once again you may want to consider listening to the tutorial on headphones or your studio monitor speakers a few times to get familiar with how the EQ works. If you’d like to dive in deeper and see how an EQ could be used specifically to improve some of your recordings in a real world scenario for you, then consider booking a one on one training session.