10mm87- mastering processing
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8/18/2019 10MM87- Mastering Processing
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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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8/18/2019 10MM87- Mastering Processing
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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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