New Gear Review: PASSEQ Passive Mastering Equalizer by SPL

There was only one good thing about 2020, at least for me: SPL didn’t put a hard time limit on how long I could use their PASSEQ before I had to send it back. This worked out to our mutual benefit. The more time I had with the EQ, the better it sounded, and the more useful it became—until it finally became indispensable, and I outright bought it. So, spoiler alert.

But arriving at my positive opinion was a bit of a journey. The EQ doesn’t offer a typical layout, and what it does give you is quite specialized. Whether or not it fits your needs is something you ought to know before you demo or purchase it, and that’s what this review attempts to do for you: to spotlight its immense benefits, highlight some of its eccentricities, and ultimately provide you with enough education to make that call on your own.

So let’s dive into this beast of an EQ and see what it is, what it does, and why it takes a minute to fully unpack its goodies.

Features

This is a mastering-grade passive equalizer, meant for precise recalls on busses of material.

Known both for their broad, tonal-shaping qualities and their inherently musical sound, passive equalizers are interesting beasts. If you’ve ever used a Pultec, that’s a passive EQ. If you’ve ever used a Pultec plug-in, that is an impression of a passive EQ. To my ear ears, there is still a significant difference between most impressions and the real thing.

The PASSEQ offers three bands (low, mids, and highs), each with their own independent boost and cut sections. You don’t get one knob to boost or cut a frequency: you get one knob to boost and another to cut.

Consider that this is a stereo unit, so all the controls are doubled; then, look at this picture of the unit and ask yourself if you truly understand it:

The PASSEQ is a powerful EQ—but its layout may not feel intuitive at first to new users. Are the rewards worth the learning curve? Nick Messitte reviews.

I found the layout of this EQ discombobulating at first. Most equalizers are as easy to read as a book: the lows are on the left, the highs are on the right, and from one syntactical end to the other, your midrange bands are arranged like words in a sentence.

Not so with the PASSEQ—this thing goes a different route altogether. A prominent, oversized, output-gain attenuator (or “volume knob”) serves as a bullseye, and around this bullseye you’ll find all the other pertinent controls. Frequency selectors and gain knobs encircle the target. Your cuts sit on the left of the big volume knob; your boosts lie to the right. The orientation from bass to treble doesn’t move from left to right, but from bottom to top.

So yeah, it takes a minute to get used to how this piece works. Once you do, it actually makes a ton of sense. There comes a moment when the layout reveals itself to your brain, and the whole thing becomes second nature. But the road from “understanding” to “knowing by feel” is paved with “no no no no I just had the perfect mix HOW DO I GET IT BACK!!!” moments.

Except for the high-band boost, there are no selectable Q controls. Every Q has been pre-tuned to the manufacturer’s idea of what is best. You might find this annoying, but that’s asking an apple to be an orange: this is a broad-strokes piece rather than a surgical device. With acceptance, I didn’t miss them at all. The boosts add flavor with gusto, the cuts subtract nastiness with subtlety—and you have one less control to worry about.

As with the PQ, the PASSEQ utilizes SPL’s VOLTaiR technology, and this means one glorious thing: 120V rails. These, the company tells us, allow for greater dynamic range and a higher degree of headroom.

In practice, I’ve found this to be true, from the euphonic quality of the signal path, to the functional operation of the gain knobs, which keep the signal clean as you boost or cut.

Indeed, these prominent output knobs make for a wonderful gainstage, particularly as a low-end boost (or even a low-end cut) can raise the overall level. So, attenuating the level after boosting the lows comes in handy.

These knobs also provide a clean boost or cut into any downstream processor—and I’ve come to find this indispensable. You can, for example, juice the input on any compressor that doesn’t have a selectable input. Conversely, if equalizing after compression is your bag, and you enjoy driving something like a vari-mu for color, you’ll find these knobs useful in trimming the signal on the way into the next processor. You’ll get all the flavor without the level jump.

A final feature to highlight here: every control is detented, though some knobs are more fiddly than others. Oh, and there’s an auto bypass switch, but I never use them (see my SPL PQ review to read more about those).

In Use

So, truth be told, my first experiences with this product led me to believe I wouldn’t be reviewing it favorably. Don’t get me wrong, the sound when you switch the unit into the circuit is quite nice. Observe this mix, run through my pitch/catch chain, without the SPL PASSEQ:

And here it is run through the chain, with the EQ in flat.

On a purely subjective level, I note that the bass synth feels closer to me, while the drums seem to envelope the bass pattern more. The hi-hats and high-end percussion, in particular, feel more situated. A null test shows us there are in fact differences between a straight pitch/catch loop and the EQ flipped into the circuit:

I find this tone both beneficial and euphonic. However, I couldn’t wrap my head around the layout, and I often made choices that didn’t wind up suiting the tune—at least, not at first. I’d flip the unit in and out, and find myself messing up my mixes.

Then, I changed my mental framework: I asked myself, what would happen if I put this processor on a drum buss? What happens if I put it on bass instruments? These questions coincided with a project I was working on at the time—an album of experimental synth music for the band Small Prizes. Here I decided to start using the processor on the drums and basses.

Listen to the opening of this tune, without the PASSEQ in use:

And here it is with the EQ in place.

My god, that roundness in the kick drum! The sense of depth of the bass when it enters! And of course, the sheer dimensionality the processor adds—the weight is just what I want. When the bass enters, you can hear how the EQ adds the necessary frequencies to help the kick drum cut through, without sacrificing any of the roundness I’d want out of the part.

So that was a win.

As that project went out, another one came in—this time, a live concert for a fundraiser streamed over the internet. Here I tried running the vocals through the PASSEQ. They were recorded with an SM58 into a digital mixer, and I wasn’t liking my results when staying in the box.

Here’s what the vocals sounded like, with their effects, without the SPL PASSEQ:

And here’s with the processor switched in:

It’s subtle—I wasn’t cranking any one band—but the tonal shaping brings more of a pleasant tone, and mitigates the “SM58” feel of the original vocal. I certainly appreciated the processor in the full mix:

Using the EQ in the mix helped me re-evaluate how to juice the EQ on a master. With an ear trained to how the PASSEQ interplays with other pieces of my chain, I started experimenting again on the big picture. I learned, for instance, that the low-end of this EQ pushed into a subtle amount of triode on my HEDD 192 can be amazing on metal tunes.

I also learned that a “dab will do ya” on some bands, but you can go ludicrously high on others. As of this writing, I produced a master where three clicks of the lows on 54 Hz were all that I needed, but when it came to filtering out some annoying high-midrange, I had the freedom to crank 800 Hz up quite high without sacrificing much else.

Again, here’s a before and after. This is the tune “Another Friday Night News Dump” by Leland Sundries, first without the PASSEQ:

And now with the PASSEQ engaged:

At this point, I had the EQ for some time, and I was able to conclude the following: this unit has a dimensional, beefy low-end that goes beyond all my plug-ins in a wonderful way—a manner I cannot, as of yet, replicate in the box. It’s a wonderful tonal complement to a surgical unit, which is just how SPL intended it.

To Be Critical

As detailed above, the sheer learning curve makes testing this unit a deeply involved process. For me, this wasn’t an “ah ha”, magic-sauce processor; extended time with the unit resulted in a sale for the company, but if I’d only had two months, I probably would’ve sent the unit back and given it a different review. Given three to four months of use, the EQ went from “it’s not for me” to “it sounds pretty great on drums and basses” to “okay I need this on about 60% of my projects.”

Once I learned how to use this beast, I began to appreciate the immediate dimensionality and warmth it gave to projects. It may only be on 60% of every master that comes through here, but it sits on every mix. Since adding it to my arsenal, I get fewer notes, and have to work less hard on surgically sculpting any item running through it. That alone is worth the price I paid.

This of course is anecdotal, but if you trust what I say, perhaps it would be the same for you.

But enough about the good stuff. This is the section where I’m supposed to lambast the damn thing! So here goes:

The output level knobs are fiddly. You can easily bump them without realizing, and then spend a few seconds wondering why the left channel is suddenly louder until you remember that, oh right, the output knobs are fiddly.

…And that’s about it. That’s the only drawback. The learning curve I spoke of before isn’t much of a detriment—it makes you appreciate the EQ all the more after you’ve used it.

Summing it Up

I believe SPL have made a sizable contribution here to the world of mastering-grade passive equalizers. But I’d like to spend some time in this conclusion illustrating something else: this is actually the second iteration of the PASSEQ. The first, which came out a number of years ago, differed in the range of each band. A common criticism was that the low-mids didn’t go low enough, making it hard to take out offending mud. SPL listened, and offered an extension of frequencies in this remake that covers the gamut.

I believe that’s important to spotlight, because it shows that SPL is a company who will listen to customer feedback and take it into consideration. Given that fact, I’m glad I took the time to truly listen to this EQ, and to learn how to unpack its secrets.

I feel that this bears repeating: this is a processor that can truly add a lot to your material, but only if you spend the time with it—and spend the money, with its hefty MSRP of $5,499. It takes time to communicate its esoteric layout into rote memory. It takes time to figure out exactly how far you can push the bands, and how you can overlap them.

It takes time, but I believe it’s time well spent.

– As a composer of musicals, Nick Messitte has seen his work enjoy the stages of Edinburgh’s Fringe Festival and New York’s Musical Theater Festival to critical acclaim; as a guitarist, he’s played with internationally renowned musicians, including Sam Rivers, Hawksley Workman, Gary Thomas, Devin Grey and Daniel Levine. Nick is also a sound designer of theater and film (with credits such as the award winning I Hate Myself and Sumi) and a producer/engineer of records (credits include Bullet Proof Stocking’s critically acclaimed EP Down To The Top, which Nick mixed, mastered, and supplied with additional instrumentation). Lastly, he is a writer/cultural critic, whose musings can be seen regularly at Forbes.com.

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