AES Section Meeting Reports

Los Angeles - March 26, 2013

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On Tuesday, March 26, DSP algorithm wunderkind Fabrice Gabriel from Eiosis/Slate Digital began his whirlwind, yet wide-ranging
tour of equalization with a brief overview of the history of frequency-
response modification, from the discovery of the sonic effects
of seashells to Helmholtz resonators, to more modern products
like the Pultec EQP-1A and the parametric equalizer. He then
described and discussed the three primary types of digital filters:
Infinite Impulse Response (IIR), Finite Impulse Response (FIR)
and Fast Fourier Transform (FFT). Using a software application
he developed, Gabriel demonstrated how a filter acts as a resonator,
showing the effects of a filter's frequency and bandwidth on
an impulse response as he adjusted them in real time.
The discussion turned to the factors that influence the sound
characteristics often associated with equalizers — their nonlinearities,
the dynamic reactions of analog circuits to various frequencies,
topologies, and interactions among frequency bands — as
well as the greater influence of how the user adjusts settings to
please their ears, the resulting behavior from the settings, and
how the algorithm reacts to them.
Gabriel contrasted the artifacts of analog equalizers to those of their digital descendants and compared common digital EQ algorithms,
highlighting their relative strengths and weaknesses. Returning to his software application, he demonstrated how the
"Character" control he designed for his forthcoming AirEQ plug
-in minimizes the effect of steep frequency boosts on the
length of an impulse response.
He proceeded to the practical application of equalization in
mixing situations, beginning with the importance of acoustics
and microphone techniques in source recordings. He demonstrated
how subsequent attempts to counteract acoustic nulls
with EQ boosts at the affected frequencies just create resonances
that smear transients and reduce clarity. This revelation
lead to a discussion of the importance of listening while
applying EQ. Gabriel stressed the importance of relying on
one's ears and focusing attention on timbral characteristics,
rather than relying on visual displays of the frequency curves
or control positions. He spoke about the goal of building a
sonic landscape, and the distinct principles of adjusting the
frequency response and adjusting the overall balance.
After examining the practical constraints placed on equalization
by monitors, media and transmission limitations, the recently enacted broadcast loudness regulations, and perceptual phenomena,
Gabriel concluded with a brief summary and took questions from the audience.

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