Undertone Audio MPEQ-1 Review: An EQ With Saturation on Every Band

It seems like a new plugin comes out every day. Another emulation of something from the 1940s, another dynamics processor that sucks the life out of your music, and once in a while, something that’s actually useful. The Undertone Audio MPEQ-1 is one of the useful ones.

It’s a plugin version of Undertone’s MPEQ-1 hardware EQ, but they added things the hardware can’t do and that I haven’t really seen in another plugin. I’ve only had it a couple of days and it’s already on my favorites list. Here’s what it does, how I used it on drums and bass, and where it gets a little confusing.

Quick Verdict: Is the MPEQ-1 Worth It?

• What it does well: A shape knob that turns any bell into a shelf, plus three flavors of saturation you can dial in on each band separately.
• Where it falls short: Lots of clicking to change settings, and a “distortion off” button that doesn’t turn the distortion off.
• Best for: Drums, bass and anything that needs more energy, not just more frequencies.
• Price: $149 direct from Undertone Audio, with a 14-day free trial. VST3, AU and AAX on Mac; VST3 and AAX on Windows.

The Basics: It Works Like an Analog EQ

At first glance the MPEQ-1 looks like just another hardware emulation. You get a high-pass filter, a low-pass filter (click them in or out) and four EQ bands. Like a lot of analog EQs, each band lives in its own range. The low band, for example, sweeps from 20 Hz up to 340 Hz.

Each band has a switch with three positions: boost, cut and notch. Cut is a natural, analog-style cut. Notch lets you pull in the Q and grab one tight frequency, the kind of thing you’d normally reach for FabFilter to do. You can also use your mouse wheel on every control, like most digital EQs, which is faster than dragging knobs.

The Shape Knob: A Bell That Turns Into a Shelf

This is where it gets interesting. Each band has a shape knob. Turn it, and the bell slowly turns into a shelf. Keep turning and you get a knee, and eventually a Pultec-style curve that dips a little while it boosts. With a wide Q you can get some really wild curves. (Hold Ctrl and use the mouse wheel to move the shape.)

Why that matters: say I boost a guitar at a frequency I like, but I want a little more top end too. Normally I’d grab a second EQ for a shelf. On the MPEQ-1, I keep the boost where it is and add shelf with the shape knob, all in one band. I don’t know many EQs that do that, and in the couple of days I’ve used it, it’s opened up some really useful moves.

The Real Magic: Saturation on Every Band

Click Distortion and every EQ band gets its own harmonic distortion control. This is the part that sold me. You can push harmonics into just the frequencies you’re boosting, a lot or a little, and leave the rest of the signal clean.

Undertone Audio is Eric Valentine’s company. If you don’t know his credits, look them up; he’s made a ton of records you probably love. The saturation types come from gear he actually uses:

• Tube: based on an old RCA tube mixer he’s used for years. Mostly second-order harmonics, the warmer, fuller kind.
• Solid state: based on another EQ he’s used on snares for a long time. More third-order harmonics, with more edge.
• Smooth: an algorithm from development. My guess is Eric liked how it sounded, so they kept it.

To me, harmonics are about bringing energy to a mix, and having three distinct colors per band, from units I don’t think have ever been emulated, is a big deal. If you want the deep technical version, there’s a video out there of Eric explaining the whole EQ. It’s worth searching for.

The Other Controls (and the One That Confuses Everyone)

• IO: the harmonics of the hardware unit itself. Set it flat for a clean, sterile EQ, or in for the unit’s built-in color before you add any per-band saturation.
• Linked input and output: turn the input up and the output comes down. I wish every plugin did this. You can hit the saturation harder without the track jumping in level.
• Phase flip: every EQ should have one.
• “Distortion off”: this does not turn the distortion off. It just closes the distortion window, and your saturation keeps running. “EQ off” does turn the EQ off. I wanted to call this out because it’ll trip you up.

My one other gripe: switching modes takes a lot of clicks, like cycling three times to reach solid state. I think I’ll get used to it.

In Action: Drums

On a drum bus I added a little low end on the kick and a good amount of top-end boost. As plain EQ it does what an EQ does: brighter, a bit more punch in the kick.

Then I brought in the harmonics, and it completely transformed the sound. Going through the three saturation types on the kick band gives you clearly different tones, and sweeping the shape knob on the high band changes the drum sound a surprising amount. You can dial in the top end so many different ways.

In Action: Bass

The bass on its own sounded thin and a little twangy. Here’s what I did:

1. Boosted some low end with light saturation for warmth and weight.
2. Cut the upper mids, where the twang lived.
3. Pushed a lot of harmonics into that same cut band.

That third step is the trick. Cutting the mids alone would make the bass sound small. Adding harmonics back into the band you just cut thickens it up and keeps the punch without the twang. I don’t think I could’ve gotten there with EQ alone.

With drums and bass playing together, flipping both EQs off and on was a dramatic difference: from sounding like it was recorded in your grandma’s basement to sounding like one of the best rooms in LA. Two moves, neither of them crazy.

How It Compares

If you’ve used iZotope FXEQ, the idea of processing only certain frequencies will feel familiar, but FXEQ is an effects box. The MPEQ-1 is an EQ first, with saturation built into the bands. For surgical work I still reach for FabFilter Pro-Q. The MPEQ-1 is for tone and energy.

What a Plugin Can’t Do for You

Most of my clients mix their own music first. They’re producers and singers who’ve bought the plugins, watched the reviews (some of them mine) and gotten close, but not quite there. The MPEQ-1 is a great tool. It still won’t tell you that your bass is fighting your kick at 80 Hz, or that the vocal is sitting two dB too low in the chorus.

If you’ve stacked plugins and your mix still doesn’t sound like the records you love, the plugin usually isn’t the problem. That’s exactly why I offer a free mix review: send me your rough mix and I’ll record you a personal video on what’s working, what’s holding it back, and how I’d fix it.

Common Questions About the Undertone Audio MPEQ-1

What is the Undertone Audio MPEQ-1 plugin?

It’s a plugin version of Undertone Audio’s MPEQ-1 hardware EQ: four bands with a variable shape control, high- and low-pass filters, and a notch mode. The plugin adds a separate saturation stage (tube, solid state or smooth) to every band.

What does the shape knob do?

It morphs a band from a bell into a shelf, and past that into a knee and a Pultec-style dip-and-boost curve. You can boost a specific frequency and add shelf in the same band, without a second EQ.

Why is the saturation still on after I click “distortion off”?

That button only closes the distortion panel. To remove the saturation, turn each band’s distortion amount all the way down.

How much does the MPEQ-1 cost?

$149 direct from Undertone Audio, with a 14-day free trial. Try it on your own drums and bass before you buy.

Key Takeaways

• The shape knob turns a bell into a shelf, knee or Pultec-style curve in one band
• Every band has its own tube, solid state or smooth saturation, modeled on gear Eric Valentine uses
• Cutting a band and adding harmonics back into it thickened a thin bass better than EQ alone
• “Distortion off” closes the window; it doesn’t bypass the saturation
• It’s already on my favorites list, and I think it could become a classic

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Have you tried the MPEQ-1 yet? Let me know what you’re using it on in the comments. And before you buy another plugin, send me your rough mix and I’ll tell you what’s actually holding it back.