TCM MASTERING: HOME MUSIC STUDIO PART 25 – SIGNAL PROCESSING

TCM Mastering: Home Music Studio Tips and Information

Part 25 Signal Processing – Equalisation (EQ)

Last week in the TCM Mastering Home Music Studio series, we introduced the three main types of Signal Processing – EQ, Dynamic and Effects Processing. This week and next, we will look at the three types in greater detail.

I apologise in advance, but I have no excuse for showing pictures of Hans Zimmer’s Studio, other than it makes my mouth water….just amazing! Well, it does show some of his signal processing gear.

Top – Processing Racks In Hans Zimmer’s Studio

Middle – Now That’s What I Call A Home Studio!!!

Bottom – The Command Centre.

Let’s start by looking at EQ or Equalisation. EQ is arguably the most useful of the tools available. In modern music applications it’s used in both a corrective and creative role. It allows you to adjust the frequency balance of your instruments, which should give clarity and the ability to blend everything together in the final mix.

Equalisers do this by either boosting/increasing specific frequencies, or cutting/decreasing certain frequencies.

Of course, not all equalisers are equal. Like most equipment, you will get what you pay for. Generally speaking, more expense yields better quality. Having said that, if you’re studio is based around a Digital Audio Workstation (DAW), there are some fantastic affordable software plug-ins available for the Home Music Studio engineer.

Outboard Stereo 31 Band Graphic Equaliser.

There are a few different types of equalisers.

Graphic EQs can have up to 31 frequency bands that can be boosted or cut. Each band affecting only a small frequency range.

It can be used to get rid of or reduce unwanted noise. For example, buzzes and hums are often heard, when guitar fx pedals are connected. Obviously, if you can trace the problem and get rid of the buzz or hum without EQ that is preferable. But sometimes no matter how hard you try, that buzz won’t go away.

Shelf EQ affects frequencies either above or below a target frequency.

They’re mainly used to roll off the tops or bottoms in the frequency range – good for reducing rumble (low frequency). Let’s say you’re recording a vocal or acoustic instrument with a mic and that distant traffic or air-conditioning rumble is really annoying you.

Rane Series Graphic EQ Plug-In For Pro Tools.

By applying a shelf or graphic EQ that focuses in on the offending frequency, you should be able to reduce the buzz, hum or rumble to an acceptable level, without adversely affecting the quality of the voice or instrument sound too much.

Graphic EQs tend not to be used in the mixdown stage, parametric EQs (which will be explained below) do a much better job.

High-pass and low-pass filters do pretty much what they say on the outside of the tin! They either allow high frequencies through or low frequencies through. A high-pass filter gets rid of unwanted low frequencies and…..you guessed it, a low-pass filter  prevents unwanted high frequencies getting through.

5 Band EQ By Steinberg.

Parametric EQs allow you to focus on a particular frequency and then set the width or range of frequencies around the main frequency that you want to affect.

There are three settings to consider when using Parametric EQ – Gain (which affects amplitude), Frequency and Q (bandwidth).

Gain either boosts/increases or cuts/decreases the signal. In Pro Tools you can apply the gain in a few different ways eg. by typing in a value or clicking on the plug-in EQ graph.

Frequency is self-explanatory – you select the specific frequency that needs working on.

And Q is the range (wide or narrow) of frequencies around the target frequency that the EQ settings will affect.

On many parametric EQs, there will be separate sections for low- and high-shelf EQ with their own gain, frequency and Q controls. The gain works in the same way as the parametric section, as does the frequency setting. Q represents the steepness of the shelf for the EQ. The higher the number, the steeper the shelf – that is, the narrower the range of frequencies that are affected.

Pro Tools – Digirack Parametric.

Once you get familiar with the controls of a parametric EQ, you will be able to perform precise frequency adjustments to your mix.

Different manufacturers use different values for their Q setting. But that shouldn’t matter, as you will monitor the sound (with your ears) as you affect it within the mix. In other words, it’s important that you make adjustments on what you hear not on what you see either from a frequency graph or a frequency figure readout.

One of the great things about Pro Tools, Logic and other great programmes is that there’s usually more than one way to do something. So you can develop your own way of working.

An Example Of Subtractive EQ.

Incidentally, it’s generally better to reduce gain on a frequency than to increase it, when possible. This is termed Subtractive EQ. When you boost a frequency, even with todays high quality digital plug-ins, there’s still the possibility of introducing unwanted noise.

So how would you go about getting a more solid bottom end, without boosting it? Reduce the high end. This not a universal ‘theory’ or way of thinking, but many top engineers adhere to it.

One of the great advantages of using software plug-ins as opposed to outboard gear, is that they can often be automated. So for example, you can set up an Equaliser or Chorus effect for the beginning of a vocal track and alter the settings later in the track. Record the changes with the automation. Then those changes will play back every time you go through the track.

Pro Tools Plug-Ins Can Be Automated. Choose The Parameters You Want To Automate, Then Click Add.

Another advantage of the digital world is the visual representation of the frequency you’re working on. Many plug-ins show you a picture of the frequency curve – just be sure you make your decisions by using your ears rather than your eyes to make frequency adjustments.

As I’ve mentioned in earlier blogs, the use of EQ (or any other signal processing) whilst recording should be employed carefully. First, try to get the best sound you can by using the best microphone for the job in the best position. That really is important. Check out earlier blogs on Mic Techniques and miking various instruments.

If you still feel the need for some EQ, use it sparingly.

Producer Jack Joseph Puig’s Collection Of Gear.

Once you have recorded a great instrument sound, you can then play with it as much as you want in the mix, until you’re happy with the result.

Each instrument or voice will require different EQ treatment in the mix. For a start, some instruments recorded in a Home Studio room will sound better than others.

So you may have to spend time ‘repairing’ or improving the sound of some instruments, whilst others will sit perfectly in the mix without much tinkering.

The mixing process involves balancing the various signal levels, adjusting the frequency content, dynamics and positioning the different instruments and voices spatially, usually in a stereo spread, as well as adding any effects such as reverb or chorus to enhance the final sound. We’ll delve deeper into the mixing process in a later blog.

Next week I’ll continue discussing dynamic processing and the use of effects.

Don’t forget, if you have any questions about the blog series so far, or any queries about the whole recording/mixing process – get in touch, by clicking here.

Or if you have a project that needs a session musician or three, producing, mixing or mastering – contact us for some really incredible recording and online mastering packages.

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2 Comments on “TCM MASTERING: HOME MUSIC STUDIO PART 25 – SIGNAL PROCESSING”


  1. […] Part 24 – Signal Processing. We then went on to consider in some detail, various types of EQ (graphic, parametric), dynamics (compressors/limiters, expanders/gates) and effects (reverb, echo, chorus etc). So feel […]


  2. […] Part 24 – Signal Processing. We then went on to consider in some detail, various types of EQ (graphic, parametric), dynamics (compressors/limiters, expanders/gates) and effects (reverb, echo, chorus etc). So feel […]


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