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 ! dedicated mastering

facility remains one of

the most prestigious

and expensive

elements of the

audio-production

chain. Packed with rare and

esoteric equipment, these

studios can turn the most

lifeless of mixes into a master

that plays well in every

conceivable situation – in other

words, a master you’d be happy

to put your name to! However,despite sharing many of the

same types of processors as

you’d find in a conventional

studio (namely, EQ, compression

and limiting), the design of

so-called ‘mastering-grade’

processors remains markedly

different from their studio

counterparts. So, what are these

differences, and how do they

contribute to the overall result?

Taking controlIn contrast to a traditional

mixing desk, a masteringconsole will have relatively few

controls, each specifically

focused on the demands of the

task in hand. For example, the

Maselec MTC-2 mastering

controller is designed to enable

the user to switch between

different monitoring sources

(DAT, DAW or CD, for example),

as well as audition different

insert processors. Various

compressors, EQs, limiters and

so on will be permanently

patched into the console,

enabling the mastering engineer

to quickly audition the masterwith and without any

associated processing.

Rather than providing any

flattering tonal colouration, the

ideal mastering console will

have a minimal sonic fingerprint,

with the majority of the master’s

character coming from the

selection of processors used

across the inserts. In the

Maselec MTC-2’s case,

however, there are some

exceptions to the rule, including

filtering controls to roll off

excessive high or low ends in amix, as well as its unique

Elliptical Filter. The Elliptical

Filter (a favourite tool among

many professional mastering

engineers) works at a point

below the stated cutoff point

(200Hz, for example), removing

any out-of-phase stereo

components and thus tightening

the bass end of the track.

Interestingly, the Elliptical

Filter is one of a number of

controls found on mastering

equipment that relate to the

process of cutting to vinyl, and it

offers precise control over thevertical and lateral components

of an audio signal. Rather than

carrying two discrete left and

right channel components, the

horizontal stylus motion (lateral,

in other words) carries the L/R

summed signal, while the

vertical stylus motion carries the

L/R difference signal. Given the

precise nature of what can and

cannot be pressed to vinyl, it is

important to control these two

components. Compressors such

as the Fairchild 670 or Manley

Labs’ Variable Mu (with theoptional M/S upgrade) will

therefore include Vertical/Lateral

compression modes, enabling

the mono and stereo

components of the signal to be

compressed in different ways.

The equalizerOperationally, a mastering-

grade equalizer such as the

Massenburg 9500 or Prism

Sound’s Maselec MEA-2 initially

appear to be much like any

other parametric EQ, with

Frequency, Cut/Boost and Q

controls for each band.However, one important aspect

of mastering EQ is the provision

of discrete controls for both the

left- and right-hand sides of the

mix. A mastering engineer, for

example, might decide to cut

2dB off the presence in a guitar

in the left-hand channel, but this

shouldn’t necessarily be to the

detriment of signals in the right-

hand channel. A 12kHz ‘air’

boost, on the other hand, will

probably be mirrored on both

sides of the stereo image.

 Additionally, bypass controlswill often be available for each

band (as well as global EQ

bypass), enabling the relative

amounts of cut and boost to be

individually auditioned.

Looking more closely at the

curves of the EQ, you’ll also

notice a bias to more rounded Q

curves, accentuating a flattering

cut and boost to the master,

rather than notching out sharp

frequencies. Equally, the

shelving controls may well have

distinctive curves to them

(forming a large part of their

Could the difference between conventional studio outboard and mastering-grade

processors be purely down to their price tags? Mark Cousins finds out...

Mastering processing

"#$ &'$("#&!)"#* No87

38 September 2006 MusicTech MAGAZINE

A mastering-grade equalizer will feature dedicated, identical controls for either side of the stereo image. The exact curve of the EQ

can also be engineered to produce the most flattering, musical response.

MTM42.10mm mastering 8/1/06 3:28 PM Page 1

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sonic character) that differs from

conventional shelving EQ on a

console. A Baxandall curve, for

example, produces a graduated

and continuing rise at the given

frequency point, rather than the

sharp ‘plateau’ effect usually

associated with shelving.

 Achieving the comparative air

boost on a Baxandall EQ

requires setting the Frequency

control slightly lower to achieve

the same level of excitement,

contributing a different

musicality to the EQ’ed signal.

Band on the runContrary to what most home

studio enthusiasts would

expect, the majority of

professional mastering

engineers prefer good single-

band compression – like that

offered by the Maselec MLA-2

or Manley Variable Mu – to

multi-band compression. As

well as being incredibly

expensive, single-band

mastering-grade compressors

offer a unique musical response

to the source material, resulting

in a transparent and natural

application of gain reduction.

You won’t, however, find

traditional Threshold, Ratio,

 Attack and Release controls on

such devices.

The Maselec MLA-2, for

example, works on the input-

drive principle. A ratio is

selected (from 1.4:1 to 5:1),

which in turn selects a preset

threshold. The amount of gain

reduction is then determined bythe level of input fed into the

gain-reduction stage – an

increase in gain, therefore,

applies more

compression. Given the

automatic switching of

threshold, any move towards a

different ratio won’t be met by a

dramatic increase or reduction

in the compressor’s output level

as it would on a conventional

threshold/ratio compressor. This

enables the mastering engineer

to better assess the respective

difference at different ratios

without having to compete with

differing amplitudes.

The Manley Variable Mu, on

the other hand, foregoes a Ratio

control, although it does include

a Threshold control. The

 Variable Mu concept (as

discussed in Issue 28’s 10MM

on Compression Types) works

by having a level-dependent,

variable ratio – put simply, the

harder you push a Variable Mu

compressor, the harder the ratio

becomes. For example, keeping

the threshold high and running a

low input would produce just a

few decibels of gain reduction,

equivalent to a ratio of about

1.5. Reducing the threshold and

driving the input harder will

apply more gain reduction using

a correspondingly harder ratio

(4:1 and above). Ultimately, the

 Variable Mu interaction is a

slightly trickier concept to grasp

(compared to the conventional

threshold/ratio concept), but the

results it can produce are well

worth the effort.

No limitsThe last point in the mastering

signal path is usually reservedfor a brick-wall limiter – this is

used to catch stray peaks and

increase the perceived loudness

of the finished master. Unusually,

given the predominant use of

Class A analogue processing in

the rest of the signal path,

limiting remains one of the few

areas in which digital processing

is the preferred approach. The

reason for this is simple: unlike

compression and EQ, where the

tonal colouration and sound is

so important, all a brick-wall

limiter needs to do is work

quickly, matching any movement

over the threshold with a

corresponding reduction in gain.

One of the main reasons

why digital limiters such as

Waves’ L2 Ultramaximizer work

so quickly and achieve such

precise and transparent gain

reduction is through the use of a

look-ahead buffer. The bufferholds a few milliseconds of

audio, analysing it first and then

applying the gain reduction. That

way the limiter is never taken by

surprise and is always ready to

act on any stray transients.

Mastering finesse Although few of us will ever be

in the position to afford the kind

of kit found in professional

mastering studios,

understanding some for the

principal design differences and

unique ways of working can

certainly improve our work at

home. Clearly, the design of the

equipment – from lateral/vertical

compression to the unique

curvaceous qualities of a

mastering EQ – has had a

significant impact on the sound

of recorded music to date, and

will continue to define working

practices in the future.

Promisingly, though, as a greater

amount of hardware enters the

virtual domain, we may

increasingly have more access

to these unique and interesting

forms of audio processing. MTM

MusicTech MAGAZINE September 2006 39

In contrast to a traditional mixing desk, amastering console has relatively few controls.

 For further information on some ofthe areas mentioned, visit:www.musictechmag.co.uk/mtm/features/compression-typeswww.elysia.comwww.maselec.comwww.manleylabs.com

 Check out the Gearslutz site formore on high-end audio processing:

gearslutz.com

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