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SPL Passeq Analog Code Plug-in

July 21, 2011

Software EQ with M/S processing

SPL-PasseqSPL Passeq emulates the high-end, analog passive equalizer by the same name, adding an M/S mode.



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 adjacent one.

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 side channels.

Passeq also sounded great on individual tracks. Acoustic guitar sounded smoother and sweeter, kick and bass guitar rounder and meatier.

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 bandpass filtering.

$199 MSRP

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