Review: SPL PassEq VST

Four-band fully parametric EQs have become quite the standard in the DAW domain, or rather the absolute minimum. And with that power today available in every channel, those high-end outboard things need to compare: there’s Manley’s four-band-plus-hc/lc Massive Passive, there’s GMLs 8200/9500 designs with five bands, there’s Avalon’s four-band design – all of them with multiple fully-parametric bands. And then there’s SPL’s PassEQ, marketed as a three-band EQ without anything fully-parametric.

What might make sense for a passive hardware box with 120V class-A amplifier is of course complete nonsense in the digital world. Still, SPL decided to do a plugin version as part of their revered “Analog Code” series. And I decided to get it.

What you get

The plugin is distributed, like all of SPL’s plugins, via Plugin Alliance. You get VST2 and 3 in x86 and x64, you get AU and AAX, and you get mono and stereo. From my point of view, all I need.

The plugin adds to the hardware device M/S mode (something the guys at Plugin Alliance seem to like a lot), apart from that, the plugin looks mostly like the hardware original.

Passeq_Front.jpg
Those settings actually make sense

Filter Design

The EQ is a model of a passive EQ with separate cut and boost bands. In that sense, it can also be seen as a six band EQ, but where only half of the bands can boost or cut – and that is just as well, as a typical EQ setting approach calls for equal amounts of boost and cut if you’re affecting more than one frequency. In that context, the separate bands (LF boost, LF-LMF cut, LMF-MHF boost, MF-MHF cut, MHF-HF cut and HF boost) overlap

The bands overlap to a wide degree, each one overlapping more than five octaves of the entire range from 10 Hz (lowest LF) to 20k (highest HF). From their characteristic, the two low ones are shelving-type, the mid-ones are fixed-Q peaks, the MHF-HF cut is another shelf, while the HF boost is a proportional Q-adjustable peak.

However, and here comes the tricky part, every filter is different, and changes slope etc. also with frequency and gain. Things get more confusing when you use more than one band, as everything affects everything here. This then allows for combining different bands acting on the same frequency for some complex results. As one example, you could set MF-MHF Cut, LMF-MHF Boost and HF Boost to (nearly) the same frequency and then end up with a wide-range boost, with a gentle valley in the middle, which houses a relatively sharp peak.

All in all, even with the specified three bands only, you can have a lot of variation.

But how does it sound?

In contrast to working with something like the LP10, about which I’ve talked here, the approach is completely different. Unless you’ve got a hearing calibrated to a frequency standard and a set of complex equations running in your head, you’ll most probably work the controls and see where you end up, instead of working an informed approach using a spectrum analyzer and curves which you can taylor in every respect.

The result, however, was rather astonishing to me. As part of Erlanger Programm, I didn’t have to do with somehow “crappy” sources that needed surgical fixing or restoration. I did however have to deal with your typical mixes that sound great on the studio monitors at studio listening volumes, but maybe not so much in other playback conditions.

And using the “twist knobs and see where it leads you” approach did actually work – even though the curve corresponding to the settings shown before doesn’t look that intelligent at first sight.

Passeq_Re.jpg
EQ curve corresponding to the settings above

It does however make sense upon closer inspection: the source had way too much LF and LMF content, and had lacked in the HMF department to allow the different synth brass pads to really stand out. Added is some gentle HF boost between 10k and 20k for a little bit of sparkle, and you’re set.

A EQ curve I would’ve drawn with a tool like LP10 would’ve had a much narrower boost around 2k, coming back to zero around 5k, and then a high shelf starting at around 10k and rising very steeply. But it doesn’t sound as good – I know that, because I had tried that before.

The Verdict

This is not the thing you’ll use anywhere else than on the two-bus. And if you’ve already got that base completely covered, it’s questionable if you’re willing to spend $249 just for a strange EQ. On the other hand, you could just wait for another special deal, buy it for around $60 or so, and with that get a surprisingly intuitive EQ.

If I had to name one downside of this design, then it’s the lack of a lowcut in the design. This may be different for other mixes, but in my case, where the useful frequency range often extends to 25Hz or even below that, controlling the things that come even lower is a thing I like to do – but then again, I can simply chain my LP10 for that. I still would’ve preferred to have it in the same plugin.

Apart from that, I have already come to love this EQ, and am sure that I’ll be using it regularly in the future for all of those subtle mastering chores.

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