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Understanding Equalization and Filters

April 18, 2012

Ableton Lives Parametric Equalizer: EQ Eight

In the first four posts of this new blog, I explored the basic equipment of a home recording studio, talked about some production techniques such as sampling and synthesis, and even discussed some legal information about using pre-recorded material on your tracks.  The entries were meant to highlight the techniques used during the beginning of techno and trance music production from the early 90s, and give you a glimpse of how some artists gathered sounds.  This week, I’d like to begin a new journey.  One that many newcomers have asked me from time to time, and to be honest a topic I still have questions about today – mixing.

If you are a DJ, then you already have an idea of what mixing is, if you are new to DJing or production then mixing in music is taking to songs or sounds and blending them together to create a whole new sound.  DJs use this technique to keep the flow of music going by attaching the outro of a song, with the intro of a new song so the music never stops.  In production, audio or midi is arranged on a timeline which is then processed by external units or virtual plug-ins (such as EQs and compressors) to shape the sound.  In this post, we will be concentrating on the core functionalities of EQs and filters.  They are the most essential step to getting started in mixing and a good understand of how to process certain frequencies and sounds is mandatory to getting a good mix down of your final productions.

What is Equalization?

EQ stands for equalization and when applied, it balances out frequencies with an electronic signal.  The most well-known use of equalization is in audio production and recording.  Equalization can also be used in various electronics and telecommunications such as digital television, radio and phone lines.  When equalizing a sound or frequency in music, producers and DJs use what’s called an equalizer which strengthens (boosts), or weakens (cuts) certain frequency ranges in order to clean things up or create space for other sounds.

DJ Mixer EQs or ‘Band EQ’

The most common and basic form of an Equalizer can be found on your commercial DJ mixer.  Most mixers come with a three band EQ which controls the high, mid and low frequencies.  Four band EQs can also be found on professional mixers like the Xone 92. Four band mixers offer an additional mid-range adjustment.  Equalizers on a DJ mixer are a great starting point to understand how frequency change can be applied and what it sounds like.  If you have a DJ mixer try cutting the high and low frequencies to get a filter effect.  Cutting out the mid frequencies completely and adjusting the high and low frequencies will give you an idea of what High Pass, and Low Pass filtering is.  Basic three and four band EQs found on DJ mixers usually have a set range of frequencies which they can control, and will be measured in Hz or dB (decibels).  Essentially, a DJ mixer has a slimmed down graphic equalizer.

Parametric EQs

In production, the equalizer which is most commonly used is a parametric equalizer.  A parametric equalizer has a number of filters per input channel which is useful for changing a sounds timbre.  These types of equalizers have controls for frequency selection (in Hz), ‘Q’ adjustments which changes the bandwidth, and level or gain controls which allow you to boost or cut the selected frequency range.  In studio installments, parametric EQs are used to make sounds more prominent or clean up sounds with unwanted frequencies.  For example, if you had just finished recording a vocalist and noticed that there are some unwanted low end frequencies, you can use a filter to cut them out, but lets say you wanted to cut out the low end frequencies while also boosting some high frequencies of the vocalists voice to make it more powerful.  That’s where a parametric EQ comes in.  It acts as a filter, while also allowing you to pin point problematic frequencies and adjust them as needed.

Frequency Range

If you remember from my previous post ‘Sample Banks and Sound design,’ I posted a frequency poster which gave you a visual representation of where certain frequencies lie in the mix.  Each sound you use in your productions has a specific frequency range and place in the stereo spectrum. Properly filtering or EQing out unnecessary sounds (such as the low end frequencies in a hi-hat sample)  will help make your productions sound clean and more vibrant.  A lot of times, new producers will create a track and stack sound upon sound on each other without properly learning about which sounds hold specific frequencies.  In order to help you understand better, I’ve created a basic guideline for you to follow:

0 – 80Hz: Sub-bass

80 – 250 Hz: Bass-end weight/punch

250 – 400Hz: Warmth

400 – 800Hz: Boxiness

800Hz – 1.5: Nasal

1.5 – 4 kHz: Presence / harshness

4 – 6 kHz: Crispness

6 – 8 kHz : Brightness

8 kHz+ : Air / sizzle

 

Low Pass and High Pass Filters

When trying to understand filters, its best to look at the filter as a doorway to a different room.  The more open a doorway is, the more sound will come through.  When you start to close that door, fewer frequencies are able to come through.  Lets say you have a loop that has a great hi-hat part but the low end frequencies of that loop are making your bass and kick drum sound muddy.  You can apply a High Pass filter which cuts out frequencies below the set Hz value.  So, if you want to cut all frequencies below 300 Hz, you just apply your high pass filter, set your frequency adjustment to 300 Hz and you’re good to go.  Now lets say you have a great bass line loop, but want to cut out the high pitched hissing sound which is interfering with the hi-hats.  For this you would apply a low pass filter which cuts out unwanted high end frequencies.

Essentially, if you want to do some basic filtering, stick with using a high and low pass filter to clean up your sounds and remove any unwanted frequencies.  As you become more accustomed to working with filters and wish to fine tune your sounds, jump over to a parametric EQ for more control over your timbres.

Spectrum Analyzer

A Spectrum Analyzer is a device used to measure the incoming frequencies of a sound.  It gives you a visual representation of what your sound is doing and the value of the sound in Hz and sometimes a note value depending on which analyzer you are using.  Spectrum analyzers are great for fine tuning your sounds when your ears are becoming difficult to work with.  Spectrum analyzers are also great for giving you feedback on just which frequencies you need to boost or cut in order to mix your track well.  Using EQs, filters and spectrum analyzers together is the most important role when it comes to mixing dance music, and quite possibly the only tools you need in today’s competitive music industry.  Below is a visual of what a spectrum analyzer looks like.  The orange line gives a full representation of which frequencies this sound is occupying.

Conclusion

When producing music, using EQs and filters is by far the most common tactics to processing sounds.  It is essential to creating a vibrant mix that is both clear and focused.  If you are new to EQs and filters, I recommend you play around with some sounds and boost/cut frequencies to get an idea for how these devices work.  The best way to learn is to try it out yourself.  Once again, keep things simple, and be sure to contact me if you have any questions at all.

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Much love

Markos Polydorou

mpolydorou@djmag.ca

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