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Aphex 204 Aural Exciter and Big Bottom
When Aphex first released their Aural Exciter,
over 25 years ago, it was the stuff of legend.
You couldnt even buy one; you had to rent it
by the minute, no less. Many engineers were
so enchanted with this new form of audio
voodoo that they often kept it discreetly out of
sight, invoking it surreptitiously when a bit of
magic was needed. But it wasnt a gimmick or
a sound du-jour. The Aphex Aural Exciter really
worked, and deservedly won immortality when
it was used to mix classic albums by Linda Ron-
stadt, James Taylor, and Jackson Browne. It has
stood the test of time, too. Smart producers
have been using it ever since, and really smart
producers have been keeping quiet about it.
Now the Aphex Aural Exciter is well-known
and available to everyone, and, at a list price
for less than $400, how could you afford not
to own one? You cant. After more than 25
years doing just one thing - making mixes
sparkle and tightening up the low end - the
Aural Exciter is still doing what it did in 1975,
but with improved circuitry, better sound, and
many more musical opportunities to use it. If
youre a sound designer seeking to improve
intelligibility in vocals, if you need to tighten
up, focus, or better pronounce your low end
without increasing the level (something EQs
cant do), or if you want to add sparkle to a
dull mix, the Aphex Aural Exciter 204 demands
serious consideration. It will not only save a
mix or two, it might earn you the title of Sor-
cerer of Sweetening or the Magician of Mix-
clowns.
OVERVIEW
The 204 is a dual-channel balanced processor
with a thick, brushed-chrome faceplate, sturdy
housing, and solid-feeling controls. The 204
actually sports two functions: the original Aural
Exciter harmonics generator and the equally
useful Big Bottom low-end-enhancing system.
The originally named Big Bottom - the pat-
ented circuitry for adding low-end density
without increasing the dB count - has become
Optical Big Bottom in this incarnation, owing
to an optical coupler in its works. But the basic
operation and sound-processing architecture
remain the same. So if youre already familiar
with the Aural
Exciter line, this is just mo better.
The 204s two channels are completely inde-
pendent. In addition to providing 1/4-inch TRS
and XLR jacks for both ins and outs, the back
panel offers twin operating-level switches (-10
dBV, +4 dBu) - one per channel. Since theres
no stereo link function, you could conceiv-
ably run two mono sources through the 204,
one using, say, balanced 1/4-inch jacks at -10
dBV and another signal on the XLR jacks at
+4 dBu. In practice, this doesnt come up very
much, because the 204 is best suited to treat-
ing entire mixes - which invariably come in
stereo. But its nice to know you have two
completely independent channels with their
own level switches, all the same. For stereo
processing, as long as you have the controls
set for subtle usage, you shouldnt experience
any imaging problems between the left and
right channels. To have the two channels talk
to each other would have required some extra
circuitry - a DAC, DC voltage to track the pots,
or some other solution which would certainly
have driven up the price. In careful listening,
I found no phase coherence or imaging prob-
lems.
On the front panel, each channel has six
controls: three for Big Bottom (Drive, Tune,
and
By Jon Chappell jchappell@musicplayer.com
The magic
continues
in this dual-
channel,
balanced
version of a
classic
processor
IN REVIEW
Aphex 204
Aural Exciter and Big Bottom
APHEX 204
MANUFACTURER: Aphex Systems Ltd., 11068
Randall St., Sun Valley, CA 91352, Tel: 818-767-
2929. Web: www.aphex.com.
SUMMARY: Imperative for audio restoration, and
for brightening a mix and bolstering bass; a rival
approach to any EQ or compressor.
STRENGTHS: Great sound. Inexpensive. Solidly
built. Balanced I/O. Processing doesnt compro-
mise headroom.
WEAKNESSES: No headphone or footswitch jack.
PRICE: $399
EQ FREE LIT. #: 121
DECEMBER 2001 | EQ By Jon Chappell * jchappell@musicplayer.com
IN REVIEW
Mix) and three for Aural Exciter (Tune, Har-
monics, and Mix). Those who remember the
venerable 104, a.k.a. Type C2, will notice
that Girth and Overhang are gone,
replaced by more serious-named controls.
Two other improvements over the 104 are
separate bypass switches for each channel
(previously, you could only bring both chan-
nels in and out of bypass simultaneously
with a single switch) and the addition of a
tunable high-harmonics control instead of a
single, fixed switch. Last but not least, its
got a built-in power supply, another touch
of professionalism over the 104s wall-wart
solution.
DEFINING THE DOUBLE-
ENTENDRES
Before we set up and start dialing away,
its good to know what we can expect
from a unit that doesnt fit comfortably into
the orthodoxy of staple processors such as
gates, compressors, EQs, and time-based
effects. The Aphex Aural Exciter re-creates
and restores missing harmonics to a signal.
Unlike an EQ, which can only increase the
presence of existing frequencies through
selective application of gain, the Aural Exciter
is amplitude neutral. It will not increase
the actual loudness, only the perception of
loudness. The result is an increased bright-
ness, clarity, and presence. It will not add
harmonics to material with no inherent har-
monic content (like sinusoidal signals), so
you dont have to worry about distortion.
Although its not an EQ or a compressor,
the 204 shares properties with those effects
and is ideally used in like fashion. For exam-
ple, its best to run the 204 inline, like a
dynamics processor, rather than in a send-
and-return configuration, where youd mix
the effected signal in with the original. You
can of course, run the 204 on the insert
points of the stereo bus as well.
The process also features the patented
Transient Discriminate Harmonics Genera-
tor, which means it can supply missing har-
monics in a transient, lending intelligibility
(consonants, by definition, have a leading-
edge transient), and fill out the amplitude
envelope of a signal without changing its
shape (in other words, without increasing
the gain). This should raise the eyebrows
of anyone in broadcast, where levels are
tightly regulated, and optimizing definition
and clarity in program material is a constant
pursuit.
DIALING IN EXCITEMENT
Setting up the 204 couldnt be simpler:
Plug your mixers left and right outputs
into the 204s back-panel inputs, and then
plug the 204s outputs into your mixdown
recorder or monitor system. As mentioned,
you could always hook up the 204 through
your mixers stereo inserts. If you decide
to track with it (which is reasonable if
youre recording, say, vocals with a bad
mic), simply hook it through a channels
insert point.
The manual recommends you use the
three controls on the Big Bottom and the
Aural Exciter circuitry to tune by ear. Though
the manual details the frequency ranges
youre operating in, providing you with
some clue, you really find your sound simply
by tweaking the knobs. Except for referring
to the knobs ranges (which are not on the
faceplate), I never had to use the manual.
Operation is straightforward and simple.
IN USE
I discovered that it was better to tackle any
bass issues before turning my attentions to
the Aural Exciter portion of the 204. For
really exposed, well-recorded music (like an
acoustic trio of steel-string guitar, double
bass, and hand percussion), a little bass
management was all that was needed. After
youve wrangled the low end (if necessary),
you can turn to the Aural Exciters controls,
which are Drive, Tune, and Mix. Even when
maxing out any single control, I still found
the results musical. It was only on an A/B
comparison that I found the cranked knob
strategy too much, but this was on rela-
tively healthy mixes. In subtler applications,
mixes came alive, hidden midrange material
- like a stereoprocessed rhythm guitar that
Id never heard before - came to the fore-
front.
I was most impressed with the 204 on
program material that was otherwise suf-
fering from a deficiency. For example, on
a rhythm track where the acoustic bass
was unpredictable - loud on the low notes
and too soft on the upper notes - the 204
evened out the bass, brought it forward in
the mix (where it had been buried before),
and tightened it up in the lowest regions. In
other words, it made all the right moves.
On the Aural Exciter side, it increased the
sparkle of reels of 7.5-inch tape that had
suffered from age and not-so-great analog
technology to begin with. The 204 gave me
the perfect excuse to dust off the old Revox,
load up the reels, and transfer this musically
viable but sonically dubious material once
and for all to hard disk.
One benefit of the 204 that might not
be obvious is that you can use it on back-
ground material instead of just sizzling up
foreground tracks. Because the Aural Exciter
generally tightens up a mix - filling out the
midrange, propping up and evening out
bass response, vitalizing the treble content
- its no longer necessary to keep going to
the backing tracks to fix your mix. By leav-
ing the levels alone and simply enhancing
definition, you enjoy increased dimension-
ality in your music - instruments retain their