Software EQ with M/S
SPL Passeq emulates the high-end, analog passive equalizer by the same name, adding an M/S mode.
BY MICHAEL COOPER
WHEN I reviewed the hardware incarnation of
the SPL Passeq dual-channel passive equalizer
for Electronic Musician’s sister publication Mix
four years ago, I was totally blown away by its
sweet, natural, and round sound. Now SPL has
meticulously modeled the sonic performance
of that equalizer to create the Passeq Analog
Code® plug-in. The company also added midside
(M/S) processing capabilities to the plugin,
a boon to mastering engineers and something
the hardware model lacks.
Like passive analog equalizers, the Passeq
plug-in uses separate controls to boost and cut.
The different inherent Q factors for each of
its 72 frequency selections enable you to
craft complex EQ curves by simultaneously
boosting at one frequency and cutting at an
None of Passeq’s filters are narrow enough to
effect notch-filtering or other surgical tweaks.
The plug-in’s forte is broad tonal shaping. True
to the hardware version, none of the EQ sections
have separate bypasses, an ergonomic drawback.
Like the Real Thing? I had used the
hardware Passeq on my mix bus four years ago
while mixing an acoustic ensemble. Referring
to my meticulous notes for one song, I recalled
essentially the same mix setup, using the
Passeq plug-in in lieu of the hardware unit.
(For technical reasons, the chaining of analog
compression and Passeq had to be reversed for
the new mix.)
By slightly altering my original boost and
cut settings in the plug-in, I arrived at a superb
sound that was very close to what I had achieved
with the hardware Passeq four years earlier; the
hardware evinced a little more depth, nuance,
and transparency. A/B’ing the plug-in’s active
and bypassed states, highs sounded sweeter,
mids smoother, and lows rounder with Passeq
equalization applied. It sounded as if all the
tracks had been recorded using better mic
preamps—and all my preamps are high-end.
On mastering sessions, M/S mode allowed
me to make mixes wider, apply shimmering
highs solely to stereo elements and lend
bottom-end heft to only center-panned tracks
like kick and bass. I only wish Passeq included
separate solo functions and meters for mid and
Passeq also sounded great on individual
tracks. Acoustic guitar sounded smoother
and sweeter, kick and bass guitar rounder
The Big Picture Passeq won’t handle
all your equalization needs. You’ll need an
additional equalizer or two to do high-pass,
low-pass, notch, and bandpass filtering. Passeq
is also much subtler than the vast majority of
equalizers—you’ll find yourself using a lot more
boost and cut before you hear it working. But if
delicate analog-like smoothing, a round bottom,
and silvery-sweet highs are what you’re after,
Passeq is your EQ. It sounds superb.
STRENGTHS: Superb sound quality.
72 frequency selections. M/S mode
included. Modest price.
LIMITATIONS: No separate
bypasses for EQ sections. No solos
or meters for mid and side channels.
Can’t do low-/high-pass, notch or