Tips & Techniques
Technique : Effects / Processing
If you know what you’re doing, plug‑ins are best
set by ear — but if you lack experience and take care to avoid rookie
mistakes, dialling in an off‑the‑peg preset can still prove effective...
To really understand
the finer points of a Digital Audio Workstation, you need to know how
everything works in a traditional recording studio, including processors
such as reverb, echo, compression and EQ that now exist as plug‑ins
inside DAWs. Knowledge comes with time and experience, though, so ‘first
contact’ with a DAW can be intimidating. To make life easier,
manufacturers offer plug‑in presets that you can use in typical mixing
situations. Preset sounds for plug‑in instruments can often be used with
very little tweaking, but preset processor and effects settings are
more problematic, as how well they work for you will depend on things
like the level, frequency content and dynamic range of the signal, or
the project tempo. So how can you ensure they do the job with the
mimimum of intervention?
Crossing The Threshold
Preset names can look very appealing — but how could the patch designers know what material you planned to put through them?
During our Studio SOS visits and Mix Rescue sessions,
we often see DAW projects using a compressor preset that’s not
compressing at all! The reason is obvious if you know about compressors,
but for the rest of you, here’s the story. A compressor is part of
a family of processors called ‘dynamics’ processors. These all respond
differently according to the level of the signal being fed to the
processor — and a preset designer can’t possibly know what level of
signal you’re sending to the processor! Furthermore, the greater the
difference between the quietest and loudest parts of the signal, the
greater its dynamic range, so a singer with good mic technique will
probably control their dynamic range to achieve a more consistent level
than a less experienced singer, and thus require less compression to
keep the level even in the mix. Again, the programmer of the compressor
preset can’t know how much compression your singer needs.
Level‑dependent
‘dynamics’ processors include compressors, limiters, expanders, gates
and de‑essers, and all have a threshold level that determines when
processing kicks in. Compressors, limiters and de‑essers are designed to
reduce the gain when the input signal exceeds the threshold level (they
act only on the loud bits). Gates and expanders reduce the level of the
signal when it falls below the threshold, usually to cut down the
amount of noise or spill in between the wanted portions of the audio
signal. In most cases, there will be a control called ‘threshold’, but
in some compressor designs the threshold is built into a single
‘Compression Amount’ control.
Compressors:
Typical compressors have lots of parameters that you can adjust, but if
you were to pick, say, a ‘Male Vocal’ compressor preset, the ratio,
attack and release times would probably be appropriate for vocals: all
you really need to adjust is the threshold, so that the gain‑reduction
meter shows the right amount of activity. (It’s still important to
listen, to check you’re getting the desired result!). As you lower the
threshold, more of the signal exceeds it, so more compression is
applied. Gentle compression, to even out the level, typically shows
a maximum gain reduction of about 5dB, but more assertive compression
(as you might use on rock or urban vocals) can require gain reduction of
around 10dB.
Compressors work by reducing the
level of the loudest parts of the signal, so the compressor output may
need to be ‘turned up’ to get the signal back up to its original peak
level. To this end, most compressors include an output gain control,
often called ‘make-up gain’. Some include an ‘automatic’ option for
this, but different plug-ins seem to handle this differently, and it’s
easy enough to set the make‑up gain yourself: adjust the level while
keeping an eye on the track or plug-in’s level meter, so that you end up
with a healthy signal level, while still leaving some headroom. Making
something louder will make it sound more impressive, but that’s no
different from raising the fader — so try to keep the compressed and
uncompressed signals at the same subjective level.
Spot
the difference! The compressor on the left has a threshold control,
which you adjust to suit the level of the source. The one on the right
has a fixed threshold: the input control raises the level of the source
above the threshold, so the compression kicks in, and the output control
compensates for any perceived changes in level.
Limiters: Rather than a variable threshold, plug‑in
limiters often have their threshold fixed at 0dBFS, and there’s an input
level control that can be used to boost the signal if you want to limit
the signal peaks for the purpose of maximising loudness. Essentially,
you only need to adjust the input level so that the limiter’s
gain-reduction meter shows a dB or two of activity on the loudest peaks.
If you want harder limiting, as you might on an individual drum, just
turn the gain up a little more; let your ears decide when enough is
enough.
Gates & Expanders: Like compressors,
gate and expander presets will have their attack and release times
tailored to specific applications, such as drums, vocals, guitar and so
on. Again, though, you’ll need to adjust the threshold to get them to
work correctly for your track. The simplest way to set them up is to set
the track to loop around a section that contains both wanted signal and
pauses; then, starting with the threshold at minimum, increase it until
the noise in the pauses just disappears. Don’t set the threshold any
higher than necessary to mute the noise, though, or you may start to
hear the wanted signal being affected, especially where the signal has
a wide dynamic range, or long, decaying tails. If you really want to
minimise the chance of adverse side-effects when tweaking a gate, reduce
the amount of attenuation (most gates, though not all, include
a control for this) so that instead of muting the pauses completely, you
simply reduce the noise to an acceptable level. Attenuating by between
10 and 20dB is often enough to keep the track sounding clean.
De‑essers:
De-essers vary in design, but most have a variable sensitivity control,
which essentially sets the threshold above which de‑essing takes place.
A de‑esser monitors the frequency band most likely to contain sibilant
‘S’ and ‘T’ sounds, and then applies gain reduction to that part of the
audio spectrum when loud sibilants are detected. Often there’s no
gain‑reduction meter, so you simply have to adjust the sensitivity
control by ear. What you’re after is a setting that reduces the ‘spitty’
character of those ‘S’ and ‘T’ sounds, but that doesn’t go so far as to
make the vocal sound lispy.
Some specialist
plug‑ins that reshape the envelope of a sound, or those that create
swept‑filter effects, also rely on a threshold setting to adjust how
they respond. The main exception is the SPL Transient Designer (and its
many imitators), which intelligently varies its own threshold according
to the input source, and works on material recorded at pretty much any
level.
Equalisation
How
much EQ boost and cut you apply depends entirely on the source material
and the track. To make use of EQ presets, it’s best to keep the
frequency bands fixed, but tweak the amount of cut and boost. Be careful
not to end up simply boosting all frequencies though!
When it comes to EQ, the preset designers will once
again have had to make assumptions about the source signal — so the
presets won’t be a perfect match for your track. A Male Voice EQ preset,
say, might not work in every case: for example, if there’s already
plenty of 2.5kHz attitude in the voice, you’re not going to want to
boost that band further! That said, the preset designer will at least
have carefully chosen the frequencies that are likely to have the
greatest impact on a typical male vocal — so usually the simplest way to
tweak such a preset is to focus on changing the gain setting for each
EQ band, without changing the frequency or Q. Gain or attenuation in
these bands should make plenty of difference, even with reasonably small
cut or boost settings.
Keep comparing the
result with the clean (bypassed) sound, as it’s very easy to fool your
ears into thinking louder and brighter means better! As a rule, use as
little EQ as you can get away with to do the job. Using EQ effectively
is a very necessary skill for any recording engineer, so also try to
wean yourself off presets as soon as possible. There are lots of
articles covering EQ on the SOS web site, for example at www.soundonsound.com/sos/dec08/articles/eq.htm.
After
experimenting with the gain settings, the best way to ease yourself
into parametric EQ is to experiment with varying the frequencies of the
various bands to see what audible effect that produces. When you feel
comfortable adjusting these two, move on to adjusting the Q or
bandwidth, which controls the width of the cut or boost region.
Delay
As
with compressors and most other dynamics processors, a gate (such as
the Sonalksis one pictured here) requires you to set the threshold to
make the preset settings work on your material.
There are three main adjustments you might want to
make to a delay plug‑in: how much, how long and how many repeats. If
you’re using a delay as an insert effect, the mix control determines how
much of the delay you hear relative to the dry sound. If the delay is
set up in a send/return loop, the mix control should be set to 100
percent wet. ‘Time’ determines the delay time (in milliseconds or in
musical measures), and ‘feedback’ controls how much of the delayed
signal is fed back to the input to produce further repeats. Many delays
also include a tempo‑sync feature, which is only relevant if you
recorded your song to the tempo grid, but it’s obviously helpful if
you’re programming and experimenting with different tempos.
Many
engineers record live bands without using the tempo grid, and though
this makes editing a little harder, it can free the music from the
‘tyranny’ of the click track, which, in turn, can help the song
‘breathe’ through natural small tempo changes. In such cases, you’ll
need to turn off tempo sync and set the delay time by ear.
Reverb
Reverb
comes in so many different flavours now, but back in the day, the plate
reverb was about the only game in town, and I find that it still sounds
right on almost anything. The main parameters that control the amount
of reverb are the mix setting and the decay time. As with delay, set the
mix to 100 percent wet if using in the send/return loop.
If
you’re confused by the reverb options available, try starting your
project with a vocal and a drum plate preset on two different effect
sends, and then adjust each by varying only the reverb decay time to
suit your track. You could set up more reverbs, but that’s a great place
to start.
Reverb is such a taste‑driven thing
that any judgement is purely subjective, but as a very general rule,
there’s a trend on modern records to use less obvious reverb treatments
than on those made in the ’70s and ’80s. A useful tip is to try mixing
the different reverbs you’ve set up (as described above), because the
chances are they’ll have different decay times — and that means that you
can achieve useful ‘in between’ combinations by blending them.
Enhancers & Distortion
It’s
no coincidence that the biggest dial, smack in the centre of this 112dB
Redline Reverb, controls decay time: that’s probably the first control
you should reach for when tweaking a reverb preset to suit your mix.
Typical harmonic enhancers synthesize new
high‑frequency harmonics to brighten a sound that has little or no
natural top end. If you choose a preset, the filter frequency that
determines what part of the audio spectrum will be enhanced will already
be set, so to make adjustments you need only vary the harmonics
‘amount’ control.
Distortion plug‑ins are
popular for applications ranging from adding a little warmth to a voice
or synth to making an electric guitar sound like a blender full of
barnacles! Chances are that your DAW will offer you several different
types, with presets based on each — so try them all, to get an idea of
their tonal differences, and then adjust the ‘drive’ setting to add more
or less distortion. Many types of distortion are also dependent on
signal level, so the lower your recording level, the higher the drive
setting is likely to need to be to get the same result.
Modulation
Modulation
effects include chorus, flanging, tremolo, vibrato, rotary‑speaker
effects, and so on. While rotary‑speaker plug‑ins tend to have fast,
slow and stop settings, the others are often more adjustable, and the
general rule is that if you speed up the effect, you should also reduce
the depth setting — especially when dealing with chorus and flanging. If
you simply turn up the speed of a chorus or flanger without also
reducing the depth, you’ll tend to end up with a nausea‑inducing warble —
but then I suppose that might be what you’re after, so feel free to
experiment! Some tremolo and panner plug‑ins have a tempo‑sync option,
which is worth trying if it isn’t already engaged when you open the
preset.
Channel Presets
Some
DAWs allow you to save all the plug‑ins used in a channel strip as
a kind of ‘combo’, or ‘channel preset’. These can be called up for use
on another channel, or in another project, and can save you lots of time
when working with similar material. Although they can be a great
starting point in a new project, do bear in mind that the key parameters
for each plug-in, such as a compressor’s threshold, will probably
require tweaking for every track to which the preset is applied.
The Future Of Presets?
Though
not directly related to this article, some plug‑ins, such as the Waves
Producer series and the Izotope Nectar Vocal Suite, make life easy by
hiding away the controls that you’re not likely to need to adjust. That
way, you only have to deal with the important controls — which is an
approach that’s a bit like the preset editing advice given here. I find
this a good halfway house between tweaking everything and simply calling
up presets, and because of the work that has gone into designing
them, the results can be extremely good. Maybe we’re moving towards an
era where the software treats us more like musicians and producers, and
less like engineers?
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