Music Production Techniques, Part 4: Equalizers And Filters

There are some tools an engineer simply can’t do without when successfully mixing a project, one of these is equalization. Eq’s and filters are an indispensable part of the typical mixing tool kit and have been used in studios as long as they’ve been about.

We’ll discover the different types of EQ that are available in a digital mixing environment and the difference between them. I’ll also give you some before and after audio examples, so you can hear the processors we are looking at in action.

Equalization Or Filtering?

So what is an EQ and why am I mentioning filters in the same sentence? Well the truth is an equalizer is simply a collection of filters in one handy unit. You may be used to resonant filters on a synth but these are very different due to their intense curves and synthetic nature.

Equalizers actually use a variety of different filter types including shelving, high pass, low pass and and bell to achieve their sound. Although the filter type may differ the goal is always the same and that is to alter a sounds frequency response.

Some of the filter types an EQ may include will be very close to synthesizer based filters. For example many modern EQs feature high and low pass filters in addition to the more music shelving and bell filters. These can be extremely useful for completely removing frequencies above or below a certain point.

Equalizers are really just a collection of various filters, in one handy device.

Whether you are using and EQ to solve a problem or apply a creative effect it’s useful to know the difference between the various plug-ins on your system. This way you can rest assured you have the best tool for the job.

Graphical VS Parametric

A lot of consumer products such as Hi-Fi’s, computer apps and portable players will feature something called a graphic equalizer. This is a series of faders or bands controlling specific pre-set areas of the frequency range. 

Graphic EQs are used in consumer devices but are also popular in live sound.

These are favored in consumer tech due to their simplicity and ease of use. There is however a bit of a trade off in functionality here as the frequencies that can be altered are pre-determined by the manufacturer.

Graphic equalizers are available in the professional production environment and there are some excellent graphic EQ plug-ins available, most however opt for the more flexible and capable parametric EQ.

The parametric equalizer has three main controls the centre frequency, bandwidth (or Q) and amplitude (or gain). You will generally find 3 or 4 of these groups of controls on a typical parametric EQ covering various parts of the frequency range. A Fully parametric EQ will cover the entire audible frequency range, usually with overlapping zones.

Parametric EQs are more popular in recording and mixing situations and are often found on analog consoles.

Some EQs in your collection will be fully parametric but will feature some kind of oversized display. In these plug-ins the ‘bands’ are often adjustable by dragging ‘handles’ around the display. This can be an extremely intuitive way of applying EQ to your sounds and one of my personal favorite methods.

Vintage Character And Component Modeling

When the time comes to actually choose which EQ plug-in you want to use in your mix, you have a couple of major choices to make. Of course there are literally thousands of EQ plug-ins on the market but generally speaking they fall into a couple of categories, one of which is vintage emulation, or hardware modeled EQs. 

The new Maag EQ4 is a great hardware modeled EQ.

A dry drum loop in need of some EQ:

The same loop treated with the Maag’s ‘Air Band’:

If you like your sound to have some character or you are trying to recreate the sound of a specific equalizer then these products can be perfect. They are painstakingly modeled on existing hardware, usually much sought after models with a very unique sound.

The Classic Pultec EQ has been modeled by a few manufacturers.

The Waves ‘Puigtec’ emulation used on the same loop:

Some great examples of these are the much modeled Pultec Eqs, the new Plugin Alliance Maag EQ4 and also the API models from Waves. This is just a taste of whats out there, so if you really value the sound of hardware EQs you should be spoilt for choice.

Transparent Equalization 

If you prefer something a little cleaner or just plain uninterested in adding any color to your audio you might be better off sticking with a purely digital EQ. Many DAW manufacturers include stock plug-ins as standard that are extremely transparent in nature.

Both the Logic and Cubase stock EQ plug-ins offer extremely clean outputs and can be used in applications that require a decent amount of transparency. 

Stock plug-ins that are simple digital models are often pretty transparent in nature.

Some drums being brightened by Logic’s stock EQ:

Some EQ plug-ins such as the excellent Fabfilter Pro-Q give the option to use various models. This is truly the best of both worlds as you can switch between a transparent digital model and vintage style effects in realtime.

It should be pointed out that some analog modeled EQs are actually very transparent in nature. For example SSL console based EQs have a very musical, non colored output and you should find that reproductions of these units are very clean.

NI’s Solid mix series EQs offer a really transparent, musical output.

A drum loop treated by NI’s Solid Mix EQ:

No matter which model you opt for the vast majority of these EQs can introduce a small amount of phase distortion, this is simply a pay off for their ability to operate at low latencies and with very low CPU consumption. 

Waves SSL models are also extremely clean.

If you plan to use your EQ for mastering or extremely critical buss processing at any point you may want to think about taking a different approach. We’ll take a brief look at what your options are next...

EQ In Mastering 

When equalizing an entire master or a critical drum buss at final mix down you may want a processor that delivers absolute clarity. The only real way to achieve this is to use what’s called a Linear Phase EQ.

Linear Phase equalizers ensure zero phase distortion during processing, the only downside is this super clean form of equalization does put a hefty weight on your CPU when compared with less accurate models.

Logic 9’s Linear Phase EQ is perfect for mastering.

Most DAWs supply a Linear Phase EQ and some third party products also have an option for increased latency and linear phase modes. Fabfilter’s Pro-Q shines in this area allowing varying degrees of latency control and a maximum quality mode for critical mastering jobs.

Fabfilter’s Pro-Q also supplied various Linear Phase modes.

Learn more about mixing and the role of EQ in both in these video courses.