AKARSH SHEKHAR
Why Do Similar
Equalizer Settings
Sound Different
At times?
It's a situation that every sound engineer, musician and
producer has faced. Why does the “sound" of one EQ
sound better than the other, even though they are both
set up in the same way. There's a way in which these
seemingly intangible differences can be quantified and
evaluated. We will be discussing that in this article.
To understand why equalizer settings can sound
different even with the same settings, we first
need to delve into the basics of the matter.
Equalizers have different frequency response curves
because after all, EQ is about altering the frequency
response. All equalizers have parameters for adjusting
these response curves, and each parameter affects the
sound in some way. There are three main equalizer filter
designs: highpass/lowpass, shelving, and parametric.
One of the main reasons EQs with the same settings can
sound different is because many modern EQs emulate
the analog EQs from classic consoles and outboard gear.
However, analog EQ design involves multiple tradeoffs.
For example, the designer may have wanted a steeper
slope, and was willing to trade off frequency response
or phase anomalies. It’s also worth noting that analog
EQ stages typically have some degree of phase shift.
Combining these stages together, for example with a four-
stage EQ, can produce subtle cancellations or additions
at certain frequencies. This may seem undesirable, but
it accounts for the “character” of many classic EQs.
A digital EQ that emulates one particular type of analog EQ
can indeed sound “different” when compared to a digital
EQ that emulates a different analog EQ design because
these EQs will have different frequency response curves
and slopes. Emulating a certain design doesn’t mean a
particular EQ plug-in is inherently better; however, that
particular plug-in might be better for a specific application.
For example, the SSL E Series EQ reduces Q as you increase
a band’s level, so the bandwidth remains constant at
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different gain settings. With drums, that design can have
a more “musical” result because it’s possible to combine
higher Q with lower gain for affecting individual drums.
Another difference is that the emulated EQ may have a
passive or active circuit design. Passive EQs don’t use
gain in the filter sections themselves, so theoretically the
filters can only cut, not boost. However, many passive
designs include an output amplifier that adds makeup
gain to all the filter sections, and the filters’ boost/
cut controls add a constant amount of attenuation at
the “0” setting that offsets the amount of output boost.
Therefore, when you’re boosting at a particular frequency,
the filter circuit itself is simply reducing the amount
of attenuation, which results in a “boost” by taking
advantage of the gain provided by the output amplifier.
Active EQs are variations on amplifiers, so they can
boost as well as cut and can add resonances that would
be difficult to achieve with passive EQs. Many people
consider passive EQs gentler and more “musical,”
and active EQs better at problem-solving.
Trying to differentiate among EQ characteristics is
difficult with program material because it’s a moving
target — the distribution of energy at certain frequencies
is always changing. Fortunately, there’s a simple way
to evaluate the different tonal characteristics among
different EQs: run pink noise through the EQ. Pink
noise is a test signal with equal energy per octave, so it
provides a constant, uniform way to make comparisons.
Lastly, as you adjust the settings for different EQs, you’ll
hear tonal changes that highlight differences among an
EQ’s characteristic curves. Monitoring the output visually
through a spectrum analyzer (which shows the level of
a signal at specific frequencies) further quantifies these
differences and confirms what your ears are hearing.