Reviewing Manley's Massive Passive Stereo Tube Equalizer
The following review is reprinted with permission from the October 1999 issue of Audio Media magazine. You can find Audio Media Magazine on the web at http://www.audiomedia.com.
Manley Massive PDF version with lotsa nice graphics click here (830K)
The Massive Passive, passive parametric EQ is the latest object of audio lust from the Manley team. MIKE CLUTE has the review (we think he liked it). FRANK WELLS runs the numbers.
Do not pass go, do not collect $200, go directly to your dealer and buy it... NOW! (Was that too strong?) Naw. I know; I’ve started this review all wrong, but there is absolutely no way I can wait until the end to tell you how much I love this box! EveAnna and the boys in Chino have outdone themselves with a unit that practically reinvents EQs. To a certain degree I kind of hate to call this an EQ. The Massive Passive is to EQs what steroids are to bodybuilders — it simply does things to audio you think are impossible (or at the very least, damn difficult!).
This processor is the latest in Manley’s line of well-built pro and high-end audiophile equipment, most of which utilize vacuum tube technology. The Massive Passive Stereo Tube EQ is a two-channel, four-band equalizer with high-pass and low-pass filters, gain control, and an all ‘tubes-n-metal’ signal path. The ‘Passive’ part of its title refers to the tone shaping circuits, which use no active circuitry, only metal film resistors, film capacitors, and hand-wound inductors to manipulate the sound. The tube circuitry is used to make up for the gain loss in the passive sections. I guess the ‘Massive’ part of the title could refer to the look, or maybe the transformer-balanced in/out, he physically large components, or possibly it just describes the sound of it! This unit is a ’gear-slut’s’ dream: 3U of solid brushed metal, beefy rotary pots, chrome switches, back-lit indicators, blue-lit bypass buttons and black inset metal panels with big stainless steel allen screws holding it all together. Oh... Momma!
The Manley has five high-pass frequencies and five low-pass frequencies, plus bypass on each filter section. (Frequencies: high-pass = 22, 39, 68, 120, 220; low-pass = 6K, 7K5, 9K, 12K, 18K.) These filters are extremely steep at the top and bottom and graduated to a milder slope toward the mids. This most definitely makes them rock for cleaning up the garbage. (Although I’m sure you never have garbage on your tracks!)
'Q' Me In
The Massive Passive is a constant bandwidth design, with a boost/cut of up to 20dB. The Q widens as it approaches flat, making for a gentle boost or cut at low gain settings. In most passive designs the Q gets narrower with higher frequencies — this is not the case with the Massive Passive. The narrower Q is related to the maximum boost or cut. An interesting feature is that the maximum boost is always 20dB; even if you boost two close frequencies the maximum amount, the end result is still 20dB boost, not 40dB.
Bells-n-Whistles - (Or Shelves)
Every band is switchable between Bell and Shelf curves, but that’s not the half of it. In the Shelf mode the bandwidth control is not dead. It becomes a totally new beast! Manley describes it as: “taking the interesting curves you get by boosting, plus cutting and putting them on the bandwidth control. You can dial in conventional shelf curves to ‘Full Pultec’ and then much deeper.” This is one of the things about the Massive Passive that absolutely knocked me out. It takes a bit of playing around to get the hang of, but it’s great! The other thing is, you can use double shelf curves, which is another favorite of mine — super smooth and silky on the top end, or fat and lush on the bottom!
Bring On The Band(s)
The four-band EQ section has a wide range of frequencies, 11 for each band, all of them overlapping and interleaving (22Hz to1kHz, 82Hz to 4kHz, 220Hz to 10kHz, 560Hz to 27kHz). This configuration gives about a quarter-octave resolution through the bulk of the audio spectrum and around a half-octave at the top and bottom. Every band has a boost/bypass/cut toggle switch, which is a great, though different, configuration for an EQ. It makes it a breeze to return to flat, and is also handy to look for those problem areas by boosting to find the culprit, and then cutting him out (zap!). The frequency centers are labeled thus: Low: 22Hz, 33, 47, 68, 100, 150, 220, 330, 470, 680 and 1k; Low Mid: 82Hz, 120, 180, 270, 390, 560, 820, 1k2, 1k8, 2k7 and 3k9; High Mid: 220Hz, 330, 470, 680, 1k, 1k5, 2k2, 3k3, 4k7, 6k8 and 10k; High: 560Hz, 820, 1k2, 1k8, 2k7, 3k9, 5k6, 8k2, 12k, 18k and 27k. Rather ‘British’ looking, right mate?
Things Are Heatin’ Up
There are two single-ended gain/line-amp circuits for the make-up gain. Six dual triodes are used, two 5751s and four 6414s. The ‘in’ button is actually a hard-wire bypass and it removes all the tube and EQ circuitry, as does the warm-up delay circuit. The gain control on each channel serves a dual purpose: to compensate for EQ gain (for matters of comparison between EQ settings and flat), and to allow a bit more ‘drive’ to the circuit. Remember, these are inductors and tubes that saturate and can add a nice character to your sound.
Well, not really; if you’ve read the rest of this I’m sure you know how I feel about the Massive Passive. I didn’t find an application in which the performance of this box didn’t impress me. It was wonderful as a master EQ on the 2-bus and as an individual instrument EQ while tracking. It is extremely musical, very much a ‘character’-enhancing instrument. Acoustic instruments, such as guitar, piano, overhead drums, and definitely vocals, were handled incredibly well. It always sounds very unprocessed, even with large amounts of gain. If there is a weak side, I guess it would be that it is not quite as ‘surgical’ as some of the top EQs are (if you like that sort of thing). But there is a price to pay for this much fun —$4800. I have to say, nothing I’ve ever used sounds like this, and that’s what makes it worth every penny. Now really, this one ya gotta hear!
Michael Clute describes himself as a ‘massive yet rather passive producer, engineer, and studio ower’ in Nashville.
Low band only engaged, max gain, Shelf mode, 100Hz frequency setting.
Fig. 1: Widest bandwidth.
Fig. 2: Medium bandwidth.
Fig. 3: Narrowest bandwidth.
Low band only engaged, max gain, Bell mode, 100Hz frequency setting.
Fig. 4: Narrowest bandwidth.
Fig. 5: Widest bandwidth.
Fig. 6: HPF, parametric bands out, 120Hz setting.
Fig. 7: LPF, parametric bands out, 18kHz setting.
Fig. 8: Frequency response. All bands in at zero gain, no filters.
Fig. 9: The answer.
Test and Measurement
Massive Passive is one of those rare pieces of gear that is just plain fun. It is fun to run a tune or track through the Massive Passive, exploring the possibilities it offers for control and manipulation of sound. And, it is just as much fun to play with it using test gear. Both experiences help define the character of this fascinating box.
The parametric sections of the Massive Passive use four parallel sections with three or four passive components in the signal path of each section. The parallel nature of the processing is what produces one phenomena Mike Clute described — the maximum gain is not cumulative between stages. Setting successive bands for similar settings will have about the same effect as only setting one of them.
By switching the control sections between boost and cut, the full resolution of the Gain pot is available in each mode. The center ‘Out’ position is a hardwire bypass of the corresponding EQ section, providing an accurate zero point without the use of detents (both the gain and bandwidth controls are continuous turn pots; the frequency selection is done with stepped switches). There is a great deal of interaction between the gain and bandwidth controls, and additional interaction between the gain controls of the parallel sections.
The mode of operation and position of the controls greatly affect the maximum gain available. Manley cites about 20dB available in Shelf modes with the bandwidth control full CCW, and about 12dB when CW. In Bell mode, about 20dB is available with the bandwidth full CW, and about 6dB when that control is CCW.
Modeled on Pultec-like concepts, the Massive Passive makes extensive use of inductors. Hardly a stock item any longer, inductors can be large and unwieldy. Cost and convenience are among the reasons this kind of design went out of practice — it would be tough to build a practical console using these approaches. The extra-large size of some of the custom inductors in the Massive Passive was mandated when, during listening tests and design refinement, some same-value, yet smaller, inductors (especially in the low-frequency sections) would tend to saturate. Kudos to Manley and their chief designer, Hutch, for investing time and effort into reviving these techniques. This sort of design is a lost art.
Bypass (blue LEDs off) still leaves the input amp and balanced output transformer in line. If the Massive Passive is not on, it will not pass audio. A 20-second, soft-start warm-up period is built into the unit — don’t panic if you turn a Massive Passive on and the blue LEDs in the bypass switches do not immediately seem to work. Balanced I/O is on XLRs and unbalanced on quarter-inch jacks. The unbalanced output can be switched internally to a -10dBv level, with the penalty of making the output polarity inverted relative to the input. Lugs on the rear panel provide a convenient grounding point and the ability to isolate the chassis.
The design of the Massive Passive anachronistically relied heavily on computer modeling to predict the interactions of various component values (plus a whole lot of listening, of course). The SPICE modeling software produced the frequency response illustrations in the manual — remarkably close to the curves obtained with test gear. The design of the Massive Passive yields both familiar EQ curves and some dramatically unique shapes. A conventional-looking shelf becomes progressively more radical as the bandwidth control is moved toward Narrow (Figures 1-3). Wide bandwidth settings with Bell selected are very wide indeed. Figures 4 and 5 show the difference between narrow and wide bandwidth settings in Bell mode. The filter shapes vary from the SPICE models in that the high-pass filters bottom out at about -40dBu and the low-pass at about -25dBu (Figures 6 and 7), which seems unusual but is not an apparent problem in use. Hutch has recently identified a bleed between the control stages as the reason the LPF bottoms out early; a soon-to-be-standard modification to address this problem yields about 10dB better performance, with a fringe benefit of adding an ‘icing to the high end’ — an extra bit of sheen that was pleasing to those auditioning the modified circuits.
Frequency response on the Massive Passive in bypass hardly matters — you are unlikely to leave this box set flat. If you do, you will find the box to be very flat through the audible range with a high-end bump around 30kHz. The Massive Passive actually measured slightly flatter with all bands in Boost mode (gain of zero) than with them in bypass (Figure 8). In the manual, an unusual group of settings is recommended and the reader is asked to guess what sort of curve they would produce. If you want to cheat, look at Figure 9 — this curve should sound remarkably flat for the amount of knob twisting involved, yet the characteristic sound of the tube stages would still be evident.
With controls set relatively flat, the distortion numbers of the Massive Passive are typical for quality tube gear. The first indication of what I would call ‘input clipping’ was at 20.6dBu; about 21.3dBu was required to achieve Manley’s reference 1.5 percent distortion. It is worth noting that this is below the maximum output level of many consoles — something to bear in mind when strapping the Massive Passive across a mix bus (Hutch expected a few complaints on this, but has been surprised by the lack thereof). I didn’t quite figure out how to achieve the specified 37dBu of output, though 33.35dBu is still far beyond the capabilities of most other gear.
The Massive Passive manual is educational and entertaining, with detailed discussion of the Massive Passive approach and development, as well as discussion of equalizers and EQ techniques in general. It is apparent in the package and its presentation that the Massive Passive project was a labor of love. That you will love it is predictable from its sound.
Let's do the numbers
Onset of clipping
(0.08% THD+N): 20.2dBu
1.5% distortion: 21.29dBu
(1.5% THD+N): 33.35dBu
All bands Out: 0.039%
All bands to boost/gain at 0: 0.037%
10Hz to 300kHz bandwidth: -79.6dBu
22Hz to 22kHz bandwidth: -84.0dBu
10Hz to 80kHz: -0.69 / +0.52dB
20Hz to 22kHz: -0.17 / +0.43dB
All tests performed at unity gain, all controls flat, all boost/cut controls set ‘Out’, 22Hz to 22kHz bandwidth, 4dBu reference level, 1kHz input, unless otherwise noted. Tests performed with an Audio Precision Portable One, Dual Domain test set.