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Exciter
2.1 THE AURAL EXCITER AND BIG BOTTOM TECHNOLOGIES EXPLAINED
The AURAL EXCITER is an audio processor that recreates and restores missing harmonics. Harmonics are musi-
cally and dynamically related to the original sound, revealing the fine differences between voices and various instru-
ments. Reproduced sound is audibly different than the original live sound because of the loss in harmonic detail,
often sounding dull and lifeless. The Aural Exciter adds harmonics, restoring natural brightness, clarity, and pres-
ence, effectively improving detail and intelligibility. Using the Aural Exciter on specific instruments or in the final
mix brings life back to the recording.
The original Aural Exciter patent disclosed a method for generating sonic harmonics which was amplitude depen-
dent. In nature, generally speaking, the higher the amplitude, the higher the amount of harmonics. However, there
are instances where there are high level sinusoidal waveforms, most of which should not have harmonics added,
and other instances where there are waveforms which have low level transients, which could be enhanced by addi-
tional harmonics. Our latest patent, the Transient Discriminate Harmonics Generator, can recognize transients
(transient discriminate) over a wide dynamic range and generate harmonics on them. The result is a more predict-
able and natural sounding enhancement over a wider range of inputs.
The Aural Exciter extends the high frequencies, unlike EQ’s and other brightness enhancers which only boost the
high frequencies and often alter the overall tonal balance. The stereo image is enhanced with the Aural Exciter,
resulting in a greater perceived loudness without an introduction of noise into the audio path. It should be pointed
out that the Aural Exciter is a “single-ended” process that can be inserted at any point within the audio chain.
“Single-ended” means that the unit will receive the incoming audio signal, process the program material through
Aphex’s patented Aural Exciter/Big Bottom technology, then output the effected signal with no further processing
required to achieve the desired aural qualities.
As illustrated above, the unit splits the input signal into two paths. One path goes directly to the output unmodi-
fied, while the other path, known as a sidechain, goes through the Aural Exciter circuit which is comprised of a
tunable high pass filter and a harmonics generator. The Aural Exciter circuit applies frequency dependent phase
shift and transient discriminate harmonics. The output of the Aural Exciter’s harmonic circuit is mixed back with
the unmodified signal but much lower in level. When used at nominal settings, the Aural Exciter circuit does not
add significant level to the original signal. Even though the added information is low in level, the perception is a
dramatic increase in mid and high frequencies.
The Exciter also incorporates another exclusive Aphex patent, Big Bottom, providing a stronger, more powerful
bass, increased sustain and density without an increase in the peak output. While static bass-boost EQ’s and
subharmonic generators will increase the bass energy level, the resultant large boost in peak level often increases
overload distortion. Big Bottom resembles the Aural Exciter in that a processed signal is mixed back into an
unmodified signal to produce an enhanced output signal. The sidechain path goes through the Big Bottom cir-
cuitry, comprised of a variable low-pass filter and a phase and dynamics processor.
Big Bottom circuitry dynamically contours the bass response of a complex range of shapes in the 50Hz to 200Hz
range. Big Bottom increases the perception of low frequencies without significantly increasing the maximum peak
output. The bass frequency response is dynamically optimized to isolate and enhance the lowest bass frequencies
to provide a deeper and more resonant bass.
2.0 Introduction
Input
Sidechain
Processing
Original
Signal
Output
SIMPLIFIED SIDECHAIN DIAGRAM
