Manley Labs Massive Passive EQ

Manley Laboratories' Massive Passive is a piece of equipment designed to emulate - using tubes - the best features of both vintage EQ circuits and Massenburg's parametric developments.
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My first professional equalizer was the I.T.I. MEP-230 parametric, which I bought in the early '70s. This classic piece of equipment was designed by George Massenburg, who invented the parametric EQ concept in 1971. It was wonderfully adjustable and it sounded good. I used it in the mic-to-tape path on every classical recording I made for the rest of that decade.
Product PointsApplications: Mastering; tracking; studio recording

Key Features: Tube-amplified passive stereo parametric equalizer; four separately switchable EQ bands (plus high-and low-pass filters) per channel; both shelf and bell curves available

Price: $4,800

Contact: Manley Labs at 909-627-4256


+ Parallel passive design produces curves virtually unattainable by any other equalizer

+ Overall sound quality is excellent.


- Learning curve

- High price

The Score: An immediately classic piece of gear; a Pultec on steroids; a must for anyone working in the analog domain.
Little did I guess that my favorite part of its circuit, the inductor-based high- and low-frequency shelving controls, would turn up in spades on my favorite equalizer 30 years later. Manley Laboratories' Massive Passive is a piece of equipment designed to emulate - using tubes - the best features of both vintage EQ circuits and Massenburg's parametric developments.

I love this box. Once unpacked and wired into my patch panel, it has never not been in the circuit - either in the tracking path, the mixdown path or in the monitor path. Never had I previously imagined that one device could make everything sound so much better. Its linear circuitry is so clean that I never heard any degradation whatsoever of my purist signal path- only improvements as I learned to properly tweak its multitudinous adjustments.

The Massive Passive is an equalizer unlike any other, either in concept, circuitry or execution. Unique is an overused term, to be sure but, in this case, I can think of no better one.


What's so unique about it? First off, it's passive, using only capacitors, inductors, and resistors to change the tone, just like the Pultecs of decades past. Amplification (tube, of course) is used only to make up for the 50 dB or so loss caused by all the passive circuitry. Furthermore, it does not put any of its EQ circuits within negative feedback loops, a design that made Peter Baxandall a household word in engineering circles 50 years ago.

The Manley unit's nonfeedback loop EQ placement practice is also employed in the Pultec circuits. The Massive Passive's most important feature, in my view, is that the various EQ stages are in parallel, not in series. The stages do not go over the same ground, adding to each other. Rather they interact in various subtle ways, creating EQ curves users of vintage Pultecs could only concoct using that gear's separate boost and cut controls simultaneously.

But the Massive Passive is not just an overgrown Pultec. It is a completely modern design: there's even a Burr-Brown OPA2604 op-amp and a complementary pair of transistors between each channel's input and the EQ circuit, designed to elegantly drive the (worst-case) 150-ohm load resulting from all that passive plumbing! The rest of the amplification is handled in typical modern Manley manner, by 5751 and 6414 triode tubes.

Aesthetically, the unit is simply beautiful. Designed by EveAnna Manley, and following the vision first seen in her VoxBox, the Massive Passive's 5.25" silver and black front panel is bilaterally symmetrical and features 31 rotary knobs (the odd one is the power switch, located dead center) and 16 toggle switches.

The results of eight of those switches light up appropriate panel labels (reminiscent of vintage devices such as the McIntosh C20 preamp). The most over-the-top, drop-dead gorgeous feature of the whole box is the two bright blue panel lights that engage when the circuitry comes out of standby mode.

Its rear panel is as utilitarian as its front is beautiful: an I.E.C. power connector, inputs and outputs in both XLRs and 1/4" jacks, a chassis grounding terminal strip and the power transformer itself. The output XLR connectors are transformer-balanced and floating; all four XLRs accept either balanced or unbalanced sources and loads. The 1/4" jacks are for unbalanced use only, at either +4 dBu or ö10 dBV levels; the output connectors bypass the transformers and, by the way, reverse polarity in comparison with the balanced outputs when configured (via a DIP switch) for ö10 dBV.

The Massive Passive's manual - 33 pages of detailed descriptions of each control, design philosophy, advice for specific EQ scenarios, sample curves and front-panel drawings - is a definite must-read.

Each channel has four bands of EQ, in addition to sophisticated high- and low-pass filters. The four EQ bands have many choices within their different center frequencies. The types of curves possible change when they are switched between bell and shelf modes, and when the bandwidth control is varied (continuously) between wide and narrow.

Each section can be a shelving-type curve and these shelves can have narrow or wide (or anything in between) bandwidths. Specifically, the two highest (rightmost) bands can be high-frequency shelves, while the two lowest (leftmost) bands can be switched to a low-frequency shelving mode; leaving conventional EQ design far behind.

The bell curves are moderately wide and the bandwidth control doesn't affect them a lot, but it does affect the amount of maximum boost or cut possible. The cut/boost range is specified at 20 dB. Due to the interaction with the bandwidth control, however, the maximum range in shelf mode is available only with the bandwidth set fully counterclockwise and, in bell mode, when it is set clockwise. In the opposite positions, it is said to be 12 dB and 6 dB respectively. The bottom line here is that one should not expect the markings around the gain knob to accurately indicate a particular number of dBs. Just tweak everything by ear, and smile.

Due to the parallel circuit topology, the gain controls themselves have a fair bit of interaction with each other. For example, if one sets up all four bands for 1 kHz and boosts each of them 20 dB, the total boost will be just 20 dB, not 80. The corollary of this observation is that, if one first boosts a particular frequency on one band, the next three will not seem to do anything if they are set at similar frequencies and bandwidths.

Bandwidth control is similar to the Q control found on other equalizers, but with several twists. Its effect in bell mode is the most similar to conventional EQ circuits, but the widest Q (at maximum boost) is about 1 for the lowest band, and 1.5 for the other three, while the narrowest Q is about 2.5 to 3 for all the bands and for most of the frequencies.

In shelf modes, the bandwidth control has a special function. When fully counterclockwise, the shelf curves are very similar to those of other equalizers. As the control is increased, however, a bell curve in the opposite direction begins to be introduced. For example, if one has a shelf boost, the circuit gradually adds a bell dip that modifies the overall shelf shape.

When the bandwidth control is fully clockwise, that bell dip becomes obvious. It is typically 6 dB down at the frequency indicated. The boost slope is steeper - the maximum boost may be as high as 12 dB. When the bandwidth knob is moved counterclockwise, it seems as if the shelf curve is moving farther toward the frequency extremes, but most of the change is limited to the beginning part of the slope, not the peak itself.

The frequencies available for selection are: 22, 33, 47, 68, 100, 150, 220, 470, 680 Hz and 1 kHz (for band one); 82, 120, 180, 270, 390, 560, 820 Hz, 1,200, 1,800, 2,700 and 3,900 kHz (for band two); 220, 330, 470, 680 Hz, 1,000, 1,500, 2,200, 3,300, 4,700, 6,800 Hz and 10 kHz (for band three); 560, 820 Hz, 1,200, 1,800, 2,700, 3,900, 5,600, 8,200, 12,000 16,000 and 27,000 kHz for band four. Whew! Each switch position selects a different capacitor and inductor.

Manley Labs' attention to detail shows in the fact that the two lowest and two highest frequencies, in shelf mode, are voiced differently by the action of the bandwidth controls on those particular frequencies. The result is tighter extreme low-frequency shelves and airier extreme high frequency ones.

I've even gotten a good effect by using these as subtle bass and treble controls when I'm in home stereo listening mode. The low frequency boost didn't seem to make my woofers move any more, but the sound was unquestionably bigger; similarly, the 16 kHz and 27 kHz definitely added a nice airy quality to CD playback. Please, don't write in saying that there is nothing on CDs up there; I'm just reporting what I heard.

A good analogy for the way the Massive Passive should be tweaked is to think of the differences between the performance of manual and automatic automobile transmissions. A conventional equalizer (and an automatic transmission) are simple enough for anyone to drive, but one has to put up with the gear shifting points chosen by the manufacturer (or a small, predictably symmetrical set of noninteractive EQ adjustments).

With a manual transmission (and the Massive Passive), one has much more control over the engine - but at the loss of a certain amount of operational simplicity. Different drivers can actually get different levels of performance out of the same automobile, once the transmission gets used to them. The same statement could be said of users of the Massive Passive.

One can concoct some pretty amazing EQ curves with this unit, but its operation isn't exactly intuitive - especially if you've never used a Pultec, an old Neve or even an API. The good news is that the effort spent learning to tweak it (by listening on a good monitor system using varying kinds of program material) and getting accustomed to how all the controls interact, is well-worth it. You'll acquire the ability to make just about anything sound better.

I could go on and on about the other features of the Massive Passive. I won't, but mention must be made of the configuration of the boost/cut/range layout. There's only one knob, labeled dB. It's labeled 0 in the 7 o'clock position and 20 at 5 o'clock. So how do you cut? Well, above the knob are a pair of toggle switches. The left one is labeled boost, off and cut. This is similar to the way the old Pultecs worked, except for the fact that they had separate boost and cut knobs.

The off position truly bypasses each EQ section separately. The second toggle is the switch that selects the shelf or bell mode. While we're still discussing the Massive Passive's various controls, I'll point out that the pair of high- and low-pass filters per channel have the following hinge points: 18K, 12K, 9K, 7.5K and 6K (for the low-pass circuits) and 22, 39, 68, 120 and 220 Hz (for the high pass ones.)

In use

The Massive Passive has so many sounds that I couldn't even begin to categorize them. In addition to my earlier comments about its transparency and ability to make everything sound better, I'll simply add this: On some other equalizers, one can indeed cut and boost particular frequencies, and one can hear the effects of those tweaks. My experience, however, is that, upon switching an EQ box in and out of my circuit path, I often say to myself, "Okay, so I heard what I did [fattened up the kick, smoothed out the vocal, whatever ...], but the overall sound was nicer before it went through that box. So what should I do?" You'll never hear yourself saying that with the Massive Passive. Just running through itwithout doing anything at all seems to improve the sound. So, once one starts actually EQing something, there's only one way to go: better.

The fact that just about every software company sells various plug-in effects units for just a few hundred dollars has not been lost on this reviewer. Many of my upcoming articles in PAR will detail my latest "24/96" DAW system and the various pieces of software I've incorporated into it.

Despite the current proliferation of plug-in software, sales of hardware units have not slowed; both types of effects boxes have their uses and my prediction is that the studio of the future will continue to use both hardware and software processing. Indeed, a common promotional line for software EQ plug-ins is that the plug-in in question "has that particular analog sound." The Massive Passive is the one to emulate.

And, in fact, someone has already tried to write code to mimic the Massive Passive's implementation of the so-called Pultec Curve in software. It's probably not much of a coincidence that Craig "Hutch" Hutchison, the designer of the Massive Passive, is also the consultant who assisted Waves in the development of its Renaissance EQ plug-in.

I've had a copy of that great little application running within Cubase VST/24 v. 4.1 this week - while I worked with the Massive Passive. For me, the ultimate console EQ has got to be using the Manley on stereo pairs while tracking, the Waves RenEQ plug-in on individual tracks for group submixes, and the Massive Passive, again, as a quick detour back into analog for the final mix! With 24/96, you can easily get away with that.


I'm keeping the review unit! Start looking for my classified ads in all the usual places; the Manley Passive is the proverbial "pearl of great price."