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Manley VOXBOX® Combo
Reviewing Manley's VOXBOX® Combo - by Dr. Frederick J. Bashour
The following review is reprinted with permission from the December 1997 issue of Pro Audio Review magazine. Pro Audio Review can be found on the web at http://www.proaudioreview.com.

MANLEY LABORATORIES VOXBOX Microphone Preamp Compressor/EQ/De-Esser/Limiter

I have reviewed microphone preamps, I have reviewed equalizers and I have reviewed compressors for this publication. In fact, I have reviewed Manley products in all three categories. But, along comes Manley Labs' new all-in-one micro-phone pre/compressor/EQ/de-esser-limiter in one unit, so I am off and running one more time.

Manley Laboratories introduced the Voxbox ($4,000) at the New York AES convention a couple of months ago (where it won a PAR Excellence Award). When I left the Javits Convention Center on Monday afternoon, EveAnna Manley escorted me to my waiting taxi. Under my arm was a naked Voxbox - no manual, no cardboard box, nada.


In the introduction to the extremely comprehensive 27-page manual that I received later, Manley Laboratories describes the Voxbox as a vocally-oriented combination of several of their popular single-function boxes, and then some. Manley combined its microphone preamplifier, electro-optical limiter and mid-frequency Pultec equalizer, and then began adding extra features. First, the el-op compressor was put before the microphone preamp, and then five-position attack and release controls were. Then about a dozen more frequency adjustment points were added to the mid Pultec EQ section for a total of 33, covering the full range from 20 Hz to 20 kl{z so, technically, it is no longer just a mid-frequency EQ. Finally,~ second el-op circuit designed as a de-esser and fast peak limiter was put in after the EQ.

Inside the stunning-looking three-rack space unit one can find five Manley audio transformers, six multi-tapped inductors, two fancy multi-cap capacitors, four microphone-spec JAN tubes, four Vactrol optoisolators, five regulated power supplies, six Bourns conductive plastic pots and seven Grayhill gold contact rotary switches. Despite the plethora of transformers, one can also bypass some of them and go transformerless on the two outputs. Special circuit refinements permit switching in and out the compressor or the limiteride-esser circuitry completely noiselessly - a really nice touch.

Since the unit has four basic functions (microphone preamp, compressor, equalizer, and limiter/de-esser) EveAnna designed the front panel's layout to graphically reflect these functions. Between the first two of these "function areas" is a really cool-looking curved ovoid cutout behind which is mounted a large and quite brightly-lit VU meter.

The first of the four "function areas" is the microphone preamp section. It has switches for phantom power, low-freciuencv cut below either 80 Hz or 120 Hz (and, of course, a flat position), and a polarity reversal switch which also incorporates a position to feed the compressor circuit from a line input, either rear panel mounted balanced XLR or phone jacks, or the front-panel 1/4" instrument jack. There are both an input attenuator control and a gain switch; the latter switches between 40 dB and 50 dB of gain in 2.5 dB steps.

The manual explains that this control switches feedback as well as gain and, since its compensation is optimized for 45 dB of gain, there is an interesting difference in the sound quality between the lowest gain (highest amount of feedback) p0 sition and the highest gain (lowest feedback) position. It is suggested that one should use this control to "fine-tune" the sound character and use the input attenuator to optimize level. In fact, since the line level inputs also go through all the circuitry in the microphone preamp section except the microphone input transformer, the input attenuator control also functions as a variable pad that reduces the line input's level before it hits the el-op element and tube circuit. In practice, I had it turned up most of the way when I used a microphone input, and stopped down to about 9 o'clock when I fed the Voxbox with a line-level input.

Underneath the VU meter is a five-position switch that selects what the meter actually shows. It can show input level, microphone preamp output level, EQ output level, and gain reduction levels on both dynarnic modification circuits.

The first compressor circuit (the one after the microphone input transformer and attenuator control, but before everything else in the microphone preanip stage) has the following controls: a "link" control that enables one to operate two Voxboxes as a single stereo unit (and keep the stereo image from moving around), a compress/bypass switch, a threshold control that increases compression when turned in a clockwise direction, and the two five-position attack and release adjustment rotary switches, each labeled fast, medium fast, medium, medium slow, and slow.

Specifically, the five attack times vary between 2 mS. and 70 mS., while the five release times are specified as .3, .5, 1, 2, and 5 seconds. The idea behind giving the user such unprecedented control of a circuit based on an electro-optical element is to permit the emulation of various classic compressor/limiter units; to allow special settings tailored for sources other than voice, such as drums or voice overs; and - in the slow/slow setting - to mimic manual fader gain riding. -~

The EQ section is pretty straightforward -- if you are familiar with Pultecs, that is. There are three bands, but they are labeled as "low peak," "mid dip," and "high peak." This is the typical Pultec MEQ-5 arrangement, and the philosophy is that it is better to cut than to boost. Actually, those are pretty good words to live by.

But just in case someone actually wanted to boost the mids, the new "expanded" Pultec design of this section makes that possible. The LF boost control goes from 20 Hz to I kHz with nine frequencies in between. Similarly, the HF boost control goes from 1.5 kHz to 20 kHz, also with nine frequencies in between.

So what is left to cut in the midrange? How about 200, 300, 500, 700, 1500, 2000, 3000,4000,5000, and 7000 Hz? The bottom line is that this "expanded" Pultec arrangement is incredibly flexible. Take my word for it - once you have learned to cut mids, you will find yourself boosting a lot less lows and highs.

The EQ section also contains a bypass toggle switch as well as a three-position toggle that enables the user to feed it alternately from the preamp output, the line input, or an insert point (available as a 1/4" jack on the rear panel). This arrangement permits feeding the output of the first two stages to an external box, and then back in again just in time to use the Voxbox's third and fourth stages.

The fourth section controls the second set of el-op elements, configured as a de esser or peak limiter. With only three controls - an in/bypass toggle switch, a frequency selector (3, 6, 9, 12 kHz and a flat "limiter only" position) and a threshold control, one can suitably enhance or squeeze just about any signal after it goes through the EQ circuit.

The final control is a Manley first: A power switch that is actually a two-position rotary control, not just a toggle switch. I am told that it was laid out that way not just to emphasize the uniqueness of the power on circuit (it contains a relay that mutes the outputs for about twenty seconds after power is turned off to prevent thumps), but also as a procedure for hum reduction. The AC switch is on the transformer board at the back of the unit, and only a plastic shaft goes to the front-panel knob. Next to the switch is an LED marked "ready", which lights when audio can pass. The manufacturer claims that this circuit will ignore quick "blackouts" for live sound work. The comprehensive "tune-up" pages at the end of the manual (yes, an analog device this complex is sort of like an analog tape machine, which must be electronically aligned periodically for proper performance) detail a method for bypassing this circuit, or at least shortening its delay time, if so desired.

The rear panel has the standard IEC AC connector and fuse, and two ground terminals that enable the operator to link or separate chassis and circuit grounds, link RCA jacks for both el-op stages, and the microphone input female XLR jack. Additionally, one finds four pairs of XLR and 1/4" jacks - for line input, preamp out, insert input, and EQ stage out. The two outputs can be sent unbalanced via the 1/4" jacks; the two inputs are balanced on both connectors.

In use

This is obviously a feature-laden unit, but how did it sound? In eight words: just about any way you want it to!

I patched my Neumann U 47 into the Voxbox, put on a pair of Stax headphones and started crooning away. Wow! I could not overload the Voxbox, regardless of how I configured it. I spent more than an hour playing with the various attack and release times alone, to get a good feeling for their strengths and weaknesses, and then started adjusting the EQ. Finally, I tried the de-esser circuit.

The first thing I learned was that it was possible to get many different "sounds" with this box. In one position (slow attack and medium slow release) I got it to successfully mimic an Eclair Engineering LA-LA limiter, which uses the identical electro-luminescent element as an original vintage LA2A unit. I happen to like that characteristic "pillowy" sound, but just by changing the settings to medium for both attack and release, I was immediately able to get a much more contemporary vocal sound.

I tried Manley's suggested medium fast release with medium fast attack setting for my recitation of Lincoln's Gettysburg Address and, boy, did I sound like an aggressive radio announcer! Really "in your face," as they say.

I was able to readily hear the effect of the different attack times by using plosive vocal sounds; the release times were easy to differentiate by noticing how quickly the room ambience returned during pauses.

I then tried running a line-level signal of soprano Judy Malafronte played back from a Studer Dyaxis H hard disk workstation. This was the same material I used a few months ago in a three-compressor review (PAR, July 1997) 50 I was quite familiarwith the effect of various limiters on it.

To my surprise, all the Voxbox's settings sounded good on her but, depending on the tune, I preferred either the medium/medium setting or the slow/medium slow setting. It was nice to be able to use the various settings of the Voxbox's "tube parametric compressor."

I have been able to do this to a limited extent in the digital domain, but never before in tube analog. And certainly never in either domain with such high quality that just about everything I did sounded good.

Using the EQ was like playing with an old friend; the effect of the old settings was identical to that of mid-frequency Manley

Pultecs, while the added frequency points in the highs and lows worked just as I would have predicted. There is really nothing else to say; it sounded like Manley Pultec EQ, which is to say it sounded big and ballsy -what I call "HiFi" - and very smooth.

I was slightly underwhelmed by the deesser section, but only because it was a tiny bit touchy to adjust. Since it is usually fed from the EQ output, it sees a pretty beefy signal at its input. Using the U 47 microphone with 45 dB of gain from the microphone preamp section (which gave a nominal reading on the Voxbox's VU meter), I found I had to keep the threshold level around 9 o'clock, unless I reduced the input level (of the microphone/line input section) quite a bit - something I loathed to do as it decreased the signal/noise ratio. The trouble is that de-essing (frequency-selective limiting) is such an audible effect, that it was difficult for me to do it subtly, even in the 9 or 12 kHz positions.

Usually I do not have a need for a deesser, but for those that do, this one will probably work just fine in most applications.

The sensitivity of the threshold control in the circuit's limiter position was the opposite; here I had to crank up the threshold to closer to 3 o'clock before I got the gain reduction meter to show that limiting was taking place. I was informed that Manley is very responsive to the suggestions of the early users of the Voxbox, and intimated that a small passive parts change would easily even up the sensitivity differential I described above, although the unit has already undergone sufficient experimentation and beta testing to justify the present parts values.

I should add that I did try feeding the EQ circuit directly from the line input (rather than connecting the line signal to the microphone/line first stage), but I think that the rather low (3 kHz) line input impedance, coupled with the fact that I missed the extra gain I get when I began with the first stage, resulted in a somewhat wimpy sound. Oh well, I guess I cannot have everything.

I also sent some full-range program material through the Voxbox and found that, despite the padding effect of the input attenuation pot on line level inputs, the result was not at all noisy to my ears. I was able to use the Voxbox just as a full-range equalizer which, of course, it did very well. The compressor function worked wonderfully on my old Sheffield Drum CD, especially in the medium fast attack/medium fast release position which, apparenfly, uses four separate time constants.


Well, the question I asked earlier, "What will I do if Iactually like this box?" must now be answered. The answer, of course, is that I will have to add the Manley Voxbox to the collection of equipment already filling up my control room's racks. And do not even mention the word stereo to me! Unfortunately, I have bought too much gear recently, so I guess I will have to start selling off some of my less-used stuff. Know anyone who wants a few ridiculously expensive tweaked-out vintage vacuum tube microphones?

Dr. Fred Bashour holds a Yale Ph.D. in music theory, and currently perforns as a jazz pianist and church organist, in addition to working as a classical music producer/engineer He is also a contributor to Pro Audio Review.
We are so very proud to announce that the VOXBOX was awarded a 1998 "TEC" Award by Mix Magazine! This was Manley's 4th TEC award nomination in a row and our first winner! Thanks to all the folks who voted and to everyone who supports and shares our vision and commitment to the pursuit of innovative, uncompromised design.
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Memorable Remarks
The Manley VoxBox might be the finest mic preamp / multiprocessor combo ever built. If you can justify the cost, do not shudder. Run, don't walk, to a Manley dealer or the Manley website and get one of these suckers pronto.

Rip Rowan

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