Equalization



Modern record production has come a long way from the first audio recording by Thomas Edison on a tinfoil cylinder phonograph. While the original use of audio recording was to make a faithful “record” of an event, today’s typical multitrack recordings are far more involved than capturing a few moments in time. Layer upon layer is recorded in succession, and each sound is altered and blended into a stylized representation of a song.

Signal processors are indispensable tools in the modern studio, and the most common would certainly have to be the equalizer (EQ). It’s the one processor that virtually all mixing consoles include on every channel. It is used in recording, mixing, and mastering. It is used for sound reinforcement and often used to even out the response of monitor speakers. It also shows up in less visible places like the passive crossovers in your studio speakers, emphasis and de-emphasis filters for radio broadcasting or vinyl record production, and in the AD/DA converters that allow you to record and play audio on your computer.

EQ is a tone control that allows you to emphasize or de-emphasize certain frequencies or bands of frequencies in a recording. All sounds are made up of varying amounts of energy across the spectrum of frequencies from deep bass to sparkling treble. Being able to alter the proportion of energy in parts of the audio spectrum allows you to correct problems for less-than-perfect sound sources, more effectively blend several instruments together, or enjoy purely creative power to create a more compelling musical experience. Before multitrack recording, engineers needed a tool that would allow them to balance instruments after a recording was already made. If you boosted certain mid range frequencies, you might hear the guitar better, or bring a quiet vocal out of the background music thereby saving the recording.

Several forms of EQ exist. A fixed frequency EQ allows boost and cut only at a particular frequency chosen in advance by the manufacturer. A semi-parametric EQ allows you to “sweep” across a certain range of frequencies, and boost or cut at the frequency you choose. A fully parametric EQ offers boost/cut, sweepable frequency, and also adds a variable bandwidth or Q control. When you boost an EQ band, not only a single frequency is affected, but also a certain number of frequencies to either side. The bandwidth control lets you choose how wide or narrow the band of frequencies to either side of that center frequency will be. This allows you to perform, for instance, a surgical strike on a nasty ring, or a broad, gentle lifting of the entire midrange, or anything in between. Often these EQs offer a shelving mode for the highest and lowest bands. The shelf will affect the entire bandwidth to one side of the turnover frequency, allowing you to raise or lower the entire treble or bass region.

Graphic EQ is more familiar to most people than parametric EQ. It is a collection of fixed frequency peaking filters. A 1/3 octave EQ usually offers 31 bands of EQ arranged three filters per octave (an octave being a doubling or halving of frequency, so 1 kHz is one octave above 500 Hz which is one octave above 250 Hz). Each band of EQ is 1/3 octave wide, which means it affects a fairly narrow band of frequencies to either side of its labeled center frequency. This allows you to easily see the EQ curve you are affecting. -Jay Frigoletto

Question for Jay? Visit him online at www.promastering.com or www.myspace.com/sslmixer.

Some classic EQs

Pultec EQP-1 A passive EQ with tubes based on early Western Electric patents.

Neve 1073 The legendary mic pre/EQ from the early 8000 series consoles.

API 550A Originally from the classic console, this EQ is still made today.

Some modern EQs

Millennia NSEQ-2 A very clean stereo EQ popular in mastering circles.

Manley Massive Passive Inspired by the Pultec, warm and musical.

Some affordable EQs

MACKIE Quad (Above) 30 band digital graphic equalizer for under $1,000

Speck ASC 4 band, single channel parametric EQ for about $500

Sony PTL-REQG2 Sony Oxford digital EQ plug-in for about $360

Rane SEQ-30S 1/3 octave stereo graphic EQ for about $325