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Zoom 9120 Advanced Sound Environment Processor

The 9120, Zoom's latest digital effects unit, promises reverb quality to rival units costing several times its moderate price tag. But in a world that's positively awash with effects processors, why should you make space in your rack for a 9120? Paul White finds out...

When I first heard that Zoom were bringing out the Sound Environment Processor, I had visions of a unit that could double as an air-conditioner, de-ioniser and drum-booth deodoriser — but, once again, I'd got hold of the wrong end of the metaphorical stick; the environment that it deals with is strictly acoustic!

There has been a small but significant trend of late for manufacturers to return to the concept of dedicated effects units rather than building an endless stream of multi-effects processors, Sony's R7 and Rocktron's Intelliverb being just a couple of examples. All Zoom's previous output has fallen squarely into the multi-effects camp, but the 9120 seems to be following the new trend towards processors that perform fewer simultaneous tasks but to a higher standard. While the 9120 couldn't be considered only a dedicated reverb processor, most of the effects on offer are presented singly, with a just a few combinations of two or three simultaneous effects.

Up to 99 effects patches can be stored as user programs and, as supplied, all the program locations are filled with sensible factory settings which can be modified or completely overwritten by the user. The majority of the effects fall into the reverb, pitch shift or modulated delay category, but there are one or two interesting variations, such as a surround sound simulator and a vocal canceller for Karaoke! Counting all the different types of reverb on offer, the unit can produce 22 different types of effect, including six special effects which will be covered later. What is interesting about this machine is the incredibly friendly user interface and the thought that has gone into making certain features particularly easy to use.

For the MIDI fiends out there, the Zoom 9120 has a reasonably comprehensive MIDI section which goes beyond the usual patch changing and SysEx dumping to some quite elegant real-time performance control options. Again, this is hardly breaking new ground, but the way in which it has been implemented is reassuring.


Zoom's 9120 is a stylish but lightweight 1U processor; disassembling it reveals construction techniques more often found in the consumer hi-fi market than in pro-audio. The case itself is light-gauge pressed steel, the support pillars for the circuit boards being pressed from the bottom panel. The cover is a folded, plastic-coated steel affair finished in black and secured by means of self-tapping screws. Rack ears are provided with the unit, though these may be left off for freestanding use.

The technical specification is also reminiscent of a hi-fi unit — specifically a CD player — in that the dynamic range is 90dB, courtesy of 16-bit linear sampling with 64 times oversampling. The effect bandwidth of the unit is specified at 20Hz to 20kHz for the unprocessed signal, and 20Hz to 14.5kHz for the processed signal.

Like previous Zoom effects units, power comes from an unregulated external power adaptor, the necessary filtering and regulation being accommodated within the main unit. The circuit boards themselves are resin-bonded paper rather than the high grade glass fibre used in most pro-audio products, and the components used appear to be standard devices as opposed to custom chips and ASICS. The left-hand circuit board houses the analogue circuitry, which is largely based around 4558 dual op-amps, while the digital board occupies most of the remaining space. Interconnections are made by means of numerous push-in connectors, and access for servicing is about as good as it gets.

Audio connections are by means of unbalanced jacks, with the choice of mono or stereo at either the input or output selected by inserting a plug into the left-hand socket of the pair. Slide switches next to the sockets allow operating level to be selected between +4dBm and -20dBm independently for input and output and, though I would have preferred to see a -10dBv option for better compatibility with home recording equipment, the gain controls provide sufficient leeway.

The rear panel also houses MIDI In and Out sockets, plus a small rotary control for adjusting the LCD contrast.


The control system for the 9120 sets it apart from most other processors because of its increased reliance on rotary controls and its modest number of buttons. At the far left is the input level control, which is a dual concentric device to allow independent control over the right and left input level as required. Two LEDs above this control perform the function of input level metering, each LED being a tri-colour type capable of lighting up green, orange or red. As the input level is increased, the LED lights up green, gradually changing to orange as the level is increased further. When the signal is in danger of clipping, the LED turns red. Maybe it's not as smart or as accurate as a bargraph meter, but it does the job.

A conventional rotary control sets the level of the direct and effected signal, and this constitutes one of the weak points of the machine, in that this setting isn't stored as part of a program. A further rotary control sets the overall output level.

There are two display windows on the front panel, the first indicating the current program number by means of two LED digits. Directly below this are the Up/Down program select buttons which scroll through the programs, and if the second button is held down after the first, the rate of scrolling increases — as it does on may other effects units. There is no direct program access keypad, so the only way of jumping directly to a new program is to use external MIDI program selection.

Next in line is a rotary selector knob which is circled by 10 LEDs and 10 sets of legend relating to the various effect types: Chorus; Delay; Pitch; SFX1; SFX2; E/R; Gate; Plate; Room and Hall. The dial has no pointer — the setting is indicated by the LED next to the appropriate legend, which means that when a program is called up, the correct effect is always indicated, regardless of the physical setting of the dial.

Next comes the main LCD display window, which is both informative and disarmingly simple to understand. This is used mainly to display parameters (during editing) or effect titles (during performance), and up to three parameters and their values may be displayed at one time. You can use the three 'soft knobs' next to the display to change in real time the displayed parameter values, and if an effect has more than three parameters, you can access these by stepping through to a new screen using the Page button. There is a maximum of three pages per effect so you don't have far to go to get to the parameters you want, and the current page is shown by means of a friendly little icon at the lower left-hand corner of the display.

Once a program has been edited, the Compare key may be used to switch between the original and modified programs, while the Store/Execute key may be used to store a successful edit to the same or any other program location. The adjacent cancel key may be used to cancel the current Store or Utility mode function. Oddly enough, the bypass key is labelled Effect and this cancels only the effect part of the signal, so what you're left with depends on the setting of the Output Balance control.

Finally in this section comes the Utility button, which provides access to the MIDI parameters (more detail later). For real-time control, there's a front-panel jack socket which takes an optional volume pedal or footswitch; the Zoom models are recommended by the manual — but then they would be, wouldn't they? Directly above this is the trigger button, which may be used to trigger effects such as pitch glides or tap-tempo delays. This probably wouldn't be used in performance but provides a valuable confirmation while editing. Right at the end comes the power switch, but as this unit uses an external adaptor, it is wise to switch off at the main if the unit is to be left unused for any length of time.


From the above control description, it is evident that the user has access to only a limited number of parameters for each effect. However, all the important parameters are available, and it can be argued that by stripping away all the irrelevant or obscure parameters, the user will be more likely to get on and do a spot of programming rather than rely on the factory programs.

Reverberation is indisputably the most important effect we have at our disposal, because it emulates an aspect of sound that plays a part in our everyday lives — indeed, it's because we are so familiar with reverberation that it is so difficult to emulate effectively, because our hearing soon picks out any unnatural artifacts. The character of reverb depends on the size and shape of the environment in which the original sound is played, on the materials used to build that environment, and on the relative positions of the sound source and listener within that environment.

Reverberation begins as a series of closely spaced but nevertheless individual echoes known as early reflections, but as these re-reflect from walls and objects, the pattern of reflections soon gets so dense that it merges into a homogenous sound recognisable as reverberation. Energy is absorbed not only by the surfaces these sounds encounter, but also by the air molecules within the room, so that the reverberation eventually decays. In most natural environments, the high-frequency components of the sound decay faster than the low-frequency components.

The 9120 offers a choice of Hall, Room and Plate reverb types, each with two variations (one less bright than the other), plus Gate and Early Reflections programs, the latter capable of producing reverse reverb simulations. The variable parameters depend on which type of reverb is selected. The Halls, for example, have parameters for reverb time (10 seconds maximum), pre-delay (up to 100ms) and high-frequency damping, which has the result of progressively reducing the brightness of the reverb decay to simulate natural environments of various types. The next parameter page gives control over the density of the reverb — how closely spaced the individual reflections are — and independent level control over the left and right early reflections. By changing the early reflections level, the apparent position of the listener in the room changes; lower settings are more suitable for classical and acoustic work, as the result is smoother, with a slower build-up of reverb.

The two Rooms also offer similar control over reverb time, pre-delay and high-frequency damping, while page two provides control over attack and early reflections levels. Attack appears to modify the reverb envelope and imparts a more definite attack to the reverberation, giving it a more aggressive character.

The Plates again offer the usual parameters of reverb time, pre-delay and HF damping, while the next page gives access to Attack, Density and Tone. Attack functions much as in the room program, and Density again regulates the spacing of the individual reflections. Tone is a top-cut filter arrangement that provides a consistent amount of tone shaping and doesn't vary over the reverb decay period.

"...for once the publicity bull is not far off the mark when it claims the reverb effects rival those of machines costing many times the price..."

Subjectively, the reverbs are excellent, and a comparison with several other effects units showed the overall character to be much closer to that of my Klark Teknik DN780 than to any of the budget units — both American and Japanese. There were no undesirable artifacts, such as ringing or fluttering, apart from on the bright plate settings, where such details are part of the natural sound of a plate system. It was also heartening to note that the level of background noise was almost as low as that from the Klark Teknik unit, and between 10 and 15dB better than from my budget units. This was not a precise measurement — I simply set up the reverb input levels according to the meters and then selected similar reverb types on both machines. The output level from the two reverb units (dry sound muted) was then set to be the same on my mixing console and then the input turned off. I subsequently reduced the fader setting on the mixer channel handling the noisier machine until the subjective background noise levels were similar and read off the difference in level on the desk's fader calibration marks.

The gated reverb setting is rather more comprehensive than that found on many other units, offering control over Reverb Time, Hold, and Decay, with a choice of triggering from mono or stereo inputs from the front panel trigger button or switch jack, or via MIDI Note On messages. Pre-delay can be varied, as can reverb density and overall tone. This system works somewhat like a true gated reverb, in that the original reverb is set up using the reverb decay time parameter and then gated using the gate hold and decay times. Most units simply provide a timed burst of early reflections. Tested on drums, the effect is quite convincing and has lots of variation, though it still sounds less 'organic' than doing it the hard way with a separate reverb unit and gate.

Early Reflections is a great program to use when you need to give a sound spatial identity without drowning it in a wash of reverb. What you get is a pattern of early reflections with no following reverb; the algorithm allows the user to change the size of the imaginary room, which affects the delay spacings, while Shape changes the overall decay envelope. At one extreme you get a reversed effect, where the reflections build up, and at the other extreme, they die away as they might in nature. Between the two is a setting where the reflections remain more or less constant in level until they finish. Further parameters provide control over the density of the reflections as well as low and high frequency EQ.


The Chorus section can generate three different chorus effects: chorus alone, chorus followed by reverb, and delay followed by chorus followed by reverb. The chorus itself can be modified by rate, depth and tone parameters, and the basic chorus uses eight delay taps panned in stereo to create very rich musical texture. The tap spacing can be varied, and a further parameter, known as Colour, plays some cute tricks on the modulation waveforms to create further timbral variations. Different parameters are available for the combination chorus effects, which restricts the chorus parameters to depth and rate while also providing time parameters for the mono delay and reverb where applicable.

Moving onto the delay section proper, this can produce mono delays of up to two seconds or stereo delays of up to one second, with feedback (in or out of phase) to create repeat echoes. The high-frequency response of the delays can also be modified to produce the softer character associated with tape loop echo units. Interestingly, the Utility key can be used to call up a simple delay time calculator, which makes it easy to match delay times to song tempi. It is also possible to set the delay time directly by tapping in the required time on the front panel trigger button or via a footswitch. Though the delay section offers little that is truly unusual, quality is exceptionally high and delay times adequately long.


I have never yet found a budget pitch shifter without its faults, and this one is no exception. Pitch shifting is achieved by sampling very short pieces of audio and looping them before moving onto the next section, and the loop points are nearly always evident as a dissonant modulation at higher levels of pitch shift. The Zoom is no exception, and though the glitches are less evident than on other budget processors I've used, they still cause shifted sections to sound disturbingly out of tune. For small shifts or subtle detuning, however, they work perfectly. Two shifts can be created simultaneously with a range of plus or minus 12 semitones and a combined pitch and reverb treatment is available.


The remaining effects are located in the SFX1 and SFX2 sections, the first being Karaoke. This is supposed to remove the vocal from a mix, but the effect it actually produces is more akin to listening to a loud disco from two blocks away. It is also possible to pitch shift the signal by up to four semitones in either direction, but I feel this section is best left alone unless you need to create the effect of a disco playing four blocks away!

Also on the SFX1 menu is Surround, which can be used to make a stereo mix appear wider or, alternatively, can generate an ambience signal to feed a rear amplifier/speaker system. This isn't a cheap substitute for Dolby Surround but rather seems to generate a subtle early reflections pattern treated with phase shifts to move the sound outside the boundary of the speakers. This could be very valuable for treating individual subgroups to give a mix more space.

Last in the SFX section is the Sweep Flanger, which works in five different modes, offering the various permutations of mono or stereo operation and up/down sweep. All modes feature a 3-phase modulation LFO, which produces a pleasantly rich sound. Though I've never yet heard anything to beat the noisy old Electro-Harmonix analogue flangers, this one is pretty good as digital imitations go.

Approaching full circle on the effects selector knob, SFX2 hides Pedal Pitch Shift and MIDI Harmonised Pitch Shift. In the first mode, positive or negative octave pitch glides of various rates can be set up and triggered from the trigger button (or a footswitch), or via MIDI. The pitch sweep is quite smooth bearing in mind the intrinsic lumpiness of the shifted signal anyway.

MIDI Harmonised Shifting requires some effort on the part of the user, as various shift intervals have to be mapped to-the various MIDI notes of the controlling signal. Independent shifts are possible for the left and right channels, and a User Scale utility is used to create and store note maps. Last of all comes Hold Delay; delay time may be set manually or by tapping in the tempo on the trigger button, footswitch or via the MIDI input. Any sound captured between starting and stopping the hold delay will be recirculated indefinitely, which is a convenient method of capturing and looping short musical sections.


On the surface, this is a very logical and friendly processor, but even logical and friendly processors have nitty gritty bits that have to be faced on some occasions. On the 9120, the nitty gritty bits live in a dark, secret place known as the Utility section, which is where you go when you want to change the MIDI channel the unit responds to, or to select the MIDI control change number that the unit responds to when working under real-time MIDI control. It's also from within this dark place that MIDI Bulk Dumps can be sent and received; factory programs may also be reinstalled individually when you discover your own are too embarrassing to use. It is also possible to initialise the whole machine, which restores all the factory programs and defaults, should you ever need to.

One particularly neat time-saving feature of this machine is its ability to compile a patch-to-program-number assignment table semi-automatically. Essentially, you pick the program you want to assign, press the Learn key and then send the unit a MIDI patch change number. The selected effects program is now assigned to the new MIDI program change number — easy.


In the short time I've had this unit, I've grown rather attached to its friendly, no-nonsense way of working. Other than the exemplary user interface, its strongest point is the sheer quality of its reverb programs, and for once the publicity bull is not far off the mark when it claims the reverb effects rival those of machines costing many times the price (just under £450). All the reverbs are smooth and satisfying, with enough variation to enable them to accommodate classical work — where a natural environment is sought — or pop and rock music, where a larger-than-life, bright environment is often preferred. Hand in hand with the subjective reverb quality goes the low background noise which is so vital in these days of Dolby S and digital multitracks. It is also rather nice to be able to report that there is no unnecessary delay or glitching when changing effects patches — a problem which besets many more costly processors.

Other strong points, in my book, are the shimmering chorus and flange treatments and the wonderfully clean delays. Less entrancing is the perfunctory pitch shifter, and though the MIDI harmony feature is interesting, I'm not sure how many users will have the desire or tenacity to program in all the intervals. The Karaoke feature is of dubious use for the purpose stated, but it is a useful processing effect in its own right — the more you turn up the effect, the more the bass end is accentuated at the expense of the top. The result is unlike anything you get from an ordinary tone control, so the key is to experiment and see what it can do.

Other features worthy of mention are the intriguing Surround program, which really does add width and depth to a mix or submix, and the friendly tempo tap and patch assignment learn modes. Though in many ways not as versatile as a multi-effects unit, the Zoom 9120 might well be the most cost-effective way of buying a really high-quality digital reverb — the other effects that come with it can be considered a bonus.

Further information

Zoom 9120 £449.95 inc VAT.

MCMXCIX, (Contact Details).


For: One of the best user interfaces around, excellent reverb sounds, and lower noise than most digital processors in this price range.

Against: The Mix control setting is not stored as part of a program, the pitch shifter is not up to the standard of the other effects, and the external power adaptor is inconvenient.

Summary: Though slightly more costly than your average budget reverb, the sound quality easily justifies the price.

Also featuring gear in this article

Previous Article in this issue

Girls Keep Swinging

Next article in this issue

Art Class

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Dec 1992

Gear in this article:

Studio FX > Zoom > 9120

Gear Tags:

Digital FX

Review by Paul White

Previous article in this issue:

> Girls Keep Swinging

Next article in this issue:

> Art Class

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