Waldorf Iridium Keyboard

Synthesizer
By Rory Dow

The keyboard version of the desktop version of the Quantum, is the Iridium Keyboard even better than the original synth?

In our April 2019 issue, Gordon Reid reviewed Waldorf’s ambitious new flagship instrument, the Quantum — a hybrid analogue/digital synthesizer capable of wavetable, granular, sample playback, physical modelling, virtual analogue, and even speech synthesis.

A year later, Waldorf announced the Iridium, a synthesizer based on the Quantum architecture. Instead of eight analogue/digital hybrid voices, it had 16 all‑digital voices. The Iridium was a desktop device which replaced the Quantum’s five‑octave keyboard with a 4x4 set of MPC‑style drum pads. The pads were met with mixed reviews, mainly because they weren’t velocity or pressure sensitive, but the general concept of a 16‑voice, all‑digital flagship seemed like a winner.

So Waldorf have followed up with a keyboard version of the Iridium, which we are reviewing here. The Quantum and Iridium keyboard share a similar hardware design and an almost identical sound engine. They even share presets.

The front panel retains the full‑colour touchscreen at the centre, surrounded by the most useful controls for oscillators, filters, envelopes, LFOs and effects. Waldorf have taken the opportunity to tweak the layout. For example, the Iridium adds more knobs to accommodate the dual digital filters but loses the Quantum’s dedicated Komplex modulator section (the Komplex modulator itself remains accessible through the touchscreen). The Iridium also adds a column of Macro buttons that can be programmed for various tasks.

The Quantum’s semi‑weighted five‑octave Fatar keybed with channel aftertouch is replaced by a new four‑octave design with polyphonic aftertouch. The addition of polyphonic aftertouch is most welcome. Because it’s one octave shorter, the Iridium is more compact than the Quantum, measuring 851 x 355 x 110mm and weighing 14kg. The Quantum measures 1006 x 401 x 131mm and weighs 17.8kg — a not insignificant difference.

How Many Synthesis Types?

Let’s recap on the capabilities of the Iridium and Quantum. There is much common ground so we won’t duplicate everything from Gordon’s Quantum review, but we’ll cover the important stuff. Waldorf have added some new features since the Quantum review, which are also available in the Iridium. We’ll make sure to cover those too.

An Iridium/Quantum patch has two layers. Each layer is a complete synth patch which can be stacked, key‑split, panned, and you can assign the number of voices for each layer. You can even play them bi‑timbrally by assigning different MIDI channels to each layer. Sadly, where the Quantum had two sets of stereo outputs, the Iridium only has one, so the two layers cannot be processed separately. Why, Waldorf, why?

Layers comprise three oscillators, three multi‑mode filters, six envelopes, six LFOs, a Komplex (multi‑stage envelope) modulator, and up to five effects. Layers are always saved as a pair (a ‘Multi’), but you can load individual layers from any patch.

The oscillators are the heart of what makes the Iridium so flexible. There are five choices: Wavetable, Waveform, Particle, Resonator and Kernels. Each of the three oscillator slots (six if you go dual layer) can load any oscillator type.

The Wavetable oscillator is, of course, Waldorf’s speciality. You get 85 factory wavetables, each with 128 waveforms. There’s plenty of sonic twistery on offer with control over the phase, spectrum, brilliance, key tracking and overdrive. Plus, you can choose from five different interpolation modes and four sonic modes, which affect aliasing and other desirable ‘vintage’ artefacts. You can also import wavetables from files or analyse a WAV file from the SD card slot. There is even a speech to wavetable synthesizer — type in any word or phrase, and the Iridium will synthesize a wavetable to ‘speak’ it.

The Waveform oscillator is a virtual‑analogue engine capable of the usual waveform types. But this being a flagship product, it doesn’t stop there. There is eight‑voice unison. Waldorf calls these voices ‘kernels’, not to be confused with the Kernels oscillator, which we’ll come to shortly. You can tune up to four kernels to make chords or intervals, with the other four being used for detuning and stereo spread. Every waveform has some form of PWM‑style waveshaping, and there is built‑in sync with its own dedicated sync oscillator.

The next oscillator type is Particle, which encompasses sampler, multi‑sample playback, and granular synthesis. There is a 1GB sample library on the internal 4GB flash RAM. Multi‑samples can be key and velocity split with individual loop points and start/end points. There’s even a full integrated mapping editor so you can create your own multi‑samples. Switching to Particle (granular) mode allows up to eight grains to be pitched, panned, enveloped and randomised in many interesting ways. You can automatically travel through the sample, which sets the base position from which the grains are taken, or you can automate it from just about any modulation source. The Particle oscillator is the key to realistic sample‑based patches and wild experimental ones.

The Resonator oscillator offers a flexible physical modelling algorithm using a noise source (or a sample) processed through resonant filter banks. Through tight control of exciters and harmonics, plucked strings, wind instruments, bells, chimes, percussion and many sounds you’ve never heard before can be achieved. There are plenty of on‑screen graphics to help you visualise what is happening. Although the physical modelling doesn’t always nail any specific instrument’s sound, it offers a unique sonic palette with which to layer and experiment.

The fifth and last oscillator type is Kernels. This oscillator type was not initially present when the Quantum was first released. To access it, you had to press a combination of buttons on the front panel for which there was understandably no label. Waldorf have updated the front panel of the Iridium to include a label for the shortcut. I’m not sure why they didn’t just add a fifth dedicated button, though.

Up to six kernels (oscillators) can be combined in an almost modular fashion. These kernels can be wavetables, VA waveforms or noise. Each kernel can audio‑frequency modulate any other kernel using a dizzying choice of amplitude modulation, frequency modulation, phase modulation, ring modulation and phase distortion. Kernels can even self‑modulate for feedback tricks. Each kernel has a multi‑stage envelope to control the kernel’s output volume. If this sounds complex, that’s because it is. To make it a little more friendly, Waldorf have included the ability to create templates with a macro page (five controls, each of which can control up to five different parameters). And they’ve included a great selection of presets to get you started. The Kernels oscillator is a huge addition to the Quantum/Iridium engine as it adds several flavours of FM and phase distortion to the already impressive list of synthesis types.

Incidentally, it’s not just the Kernels oscillator type that can save presets. All of the oscillators can be saved as a sub‑preset. Got a favourite vocal sample that you like granularised in a certain way? Just save it as a preset, and whenever you instantiate the Particle oscillator in any patch, it will be available to load — a brilliant touch.

The Iridium Keyboard is an octave shorter than the Quantum and weighs 4kg less, but is still an impressive‑looking instrument.

Filters

The Iridium offers no fewer than three multi‑mode filters. These are arranged as two filters and a ‘Digi Former’. This arrangement is a hangover from the Quantum, where the flexible Digi Former filter enhanced the two analogue low‑pass filters. In the Iridium, the filters combine new and old digital models based on some of Waldorf’s past and present products: SVF, Raiser, Largo, Nave, PPG and Quantum. Each model contains a selection of up to 18 modes that cover the usual low‑, band‑, and high‑pass options as well saturated and ‘dirty’ versions for added grit. The two filters can be linked in various ways to assist with the modulation of frequency and resonance.

The third filter, aka Digi Former, can also operate in other modes such as overdrive, comb filtering, bit crushing, and ring modulation. It can be placed before, after, or in parallel with the dual filters. Any oscillator can bypass the filters or send a varying mix to the dual filters and the Digi Former. In short, filter routing is highly flexible, and a dedicated routing page with graphics shows the audio signal flow update in real time as changes happen.

One significant improvement from the Quantum is that the digital filters are true stereo, making the entire signal path stereo. In the Quantum, using the analogue filters would mix the stereo oscillators down to a single channel — a compromise that Gordon Reid noted in his list of cons in his original review.

Modulation

No good synth is complete without modulation possibilities, and the Iridium certainly delivers. There are six LFOs per layer comprising the usual waveforms. Speed varies from 240 seconds/cycle to 100Hz, and all waveforms can be wave‑shaped. Each has attack and decay to fade the modulation in and out; per voice, global or single triggering; phase and delay.

There are also six envelopes: amp, two filter envelopes and three free envelopes, although they can all be assigned freely in the modulation matrix. Each envelope is DADSR with variable attack, decay and release curves plus two types of looping.

Finally, there’s the Komplex modulator — two multi‑stage waveforms, which you can blend between, warp, slew and jitter. The Komplex lives up to its name, producing a complex, looping, potentially ever‑evolving modulation source, all sync’ed to MIDI tempo if that’s your bag.

Modulation is handled by a 40‑slot modulation matrix, which should be enough for anyone. There are shortcuts for many common modulation routings, with some, like filter envelope amount or amp velocity, having dedicated front‑panel controls.

Effects

Each layer can have up to five effects chosen from a list of eight. They include phaser, chorus, flanger, delay, reverb, EQ, overdrive and compressor. Each can be used only once, so you can’t chain two choruses, for example. But they can be placed in any order.

The quality of the effects is excellent, and most parameters can be modulated for extra fun. Some effects even use the display to show helpful feedback, like the compressor, which shows a live waveform display with an overlay to show the amount of compression.

In addition to the layer effects, there is a global one‑knob compressor and bass‑boost option, both of which I preferred to leave off, but they could prove handy in a pinch.

Other Stuff

The Iridium is loaded with useful features to make operation more practical and fun, like the seven Macro buttons near the pitch and modulation wheels. They serve as programmable shortcuts. For example, I had one set up to enable glide (inexplicably, the Quantum had a dedicated button for this, but the Iridium doesn’t), another to begin sample recording, one to enable the arpeggiator, and one as a shortcut to the Favourites page. You can also use them to send a variety of MIDI messages.

The Favourites page is handy for quick access to your favourite presets — perfect for gigs. You can save up to six sets of 20 presets that can be loaded from the touch of a screen.

The Autoplay page houses the sequencer and arpeggiator. The sequencer can be up to 32 steps with lanes for pitch, note length, velocity and up to eight controller lanes for modulation. The sequencer can be used without note triggers simply as a modulation source or as a powerful SH‑101‑style sequencer. It can output MIDI, with extra options for swing, direction, and scale quantising. The arpeggiator offers the usual functions but adds 31 preset rhythm patterns, which can turn a basic arp into something much more complex.

The other Performance tabs are the X/Y pad (a modulation source that uses the touchscreen), and the Pads tab. The Pads tab is inherited from the Iridium desktop model, which has the 4x4 MPC‑style pad arrangement. The Iridium keyboard has no such pads, so these pages seem less useful. You can still use the on‑screen pads for triggering notes and chords, but there seems little point when the keyboard — in all its velocity‑sensitive, poly‑aftertouch glory — is right in front of you.

If ever there were a synthesis engine that deserves poly aftertouch, this is it. Fatar’s new TP/8SK keyboard plays like a dream. The aftertouch is responsive and highly controllable.

If ever there were a synthesis engine that deserves poly aftertouch, this is it. Fatar’s new TP/8SK keyboard plays like a dream. The aftertouch is responsive and highly controllable. Unlike many keyboards, you can control the midrange instead of jumping from minimum to maximum at the slightest touch. Waldorf have taken this a step further with a fantastic feature that adds variable attack and release lag to the pressure response. You can, for example, trigger a slow rise in the filter cutoff when pushing into the key and have a snappy release on note‑off. The possibilities for both sound design and performance are huge. The Iridium takes the top spot as my favourite polyphonic aftertouch implementation.

Fans of microtonal music will be pleased to hear that Iridium supports Scala tuning files. A built‑in tuning editor also allows quick equal spacing tunings, such as 24‑edo or any mathematical division of an octave you can think of.

How Does It Sound?

It is always difficult to summarise a synth of this complexity. There is no clear character because it offers so many choices. It may seem obvious, but it should not be the first choice for traditional analogue sounds. I think that’s true of the Quantum too. If you want Minimoog basses, get a proper all‑analogue monosynth. Neither is it the right choice for realistic pianos, brass, orchestral sounds and the like. The Iridium and Quantum excel at complex digital sounds, whether sample‑based, granular, FM, physical modelling or wavetable.

The preset library is huge. There are 4000 preset slots, many of them filled by sound‑design giants like BT, Don Solaris, Howard Scarr and Richard Devine. It’s packed with cinematic textures, alien landscapes, ever‑evolving pads, percussive sequences, ’80s polysynth emulations, sci‑fi sound effects, DX7 pianos, Berlin sequences, and PPG tributes. And enough unclassifiable experiments to keep the most leftfield preset‑junkie happy. The real pleasure, of course, is making your own.

It is a fantastic synth — so deep that you could spend decades with it and still not hear all it has to offer.

Conclusion

My first question when approaching this review was, ‘How is Iridium different to Quantum?’ Well, Waldorf could have named the Iridium the Quantum Digital. Apart from the filters and extra voices, the synthesis engines are identical. There are hardware differences — shorter keyboard, tweaked front panel, polyphonic aftertouch instead of mono, and new Macro buttons — but they are essentially non‑identical twins.

The inclusion of analogue filters in the Quantum was problematic. For the premium price, eight voices seemed too few. Then there was the loss of stereo channels when using those filters. Many oscillator types produce wide stereo signals, so it was a shame to sacrifice that for the analogue filters.

The Iridium fixes that problem. It sticks to its digital roots and keeps the stereo signal path. With the digital filters, there are more choices too. It’s not that analogue filters aren’t great — everybody loves analogue. But the Quantum/Iridium synthesis is so complex that much of a sound’s character is already decided before it hits the filters. To me, the digital filters make perfect sense here.

Then there’s the doubled voice count. There is room to breathe with 16 voices, and bi‑timbral operation is more appealing (although the lack of a second stereo output is irksome). Some people argue that there should be even more voices because it’s fully digital. After all, digital workstations in the 1990s were boasting 64 or even 128 voices. But physical modelling and granular synthesis can be CPU hungry. Cutting‑edge sound‑design tools require more CPU cycles. In reality, I never felt like I was running into voice‑stealing problems. Sixteen is a good number.

One of the most important additions is polyphonic aftertouch. It makes perfect sense in this digital playground of physical modelling, FM, granular and so on, and the Iridium is a more expressive synthesizer for having it.

From his original review of the Quantum, Gordon Reid listed three cons:

  • The lack of stereo analogue filters.
  • The lack of USB host support for storage devices.
  • The price (although he did concede that it wasn’t unreasonable, just high).

The digital filters fix the first item, as we already covered. The second was a feature added in a subsequent OS update. And thirdly, the price of the Iridium keyboard is £600$1000 less than the Quantum — a considerable saving. So, Waldorf have fixed every criticism from our Quantum review. Bravo!

If you’re in the market for a Waldorf flagship, there is the Iridium Desktop to consider. That decision is likely to boil down to space and cost. My choice would be keyboard, but if you already have a MIDI controller capable of polyphonic aftertouch, maybe the desktop version makes more sense.

In the end, it feels like Waldorf took all the feedback they got from the Quantum and rolled it into the Iridium. I think it’s a better synthesizer for it, but options are a wonderful thing. If the combination of digital and analogue appeals to you, the Quantum is still available, but the Iridium is not a downgrade at all. It is a fantastic synth — so deep that you could spend decades with it and still not hear all it has to offer.

Round The Back

Rear panel of Waldorf's Iridium Keyboard synthesizer.

The Iridium Keyboard’s rear is packed with the same connectivity as its desktop version. There’s a 12V DC power socket and switch, headphone output, stereo audio inputs and outputs on unbalanced TS quarter‑inch jacks, eight CV connectors on 3.5mm jacks, MIDI in, out and thru, sustain and control pedal inputs, USB connectors for USB MIDI computer connection, and a USB host socket for class‑compliant controllers or USB storage. Lastly, there’s a micro‑SD card slot for file transfers, backups and OS updates.

MPE & CV Integration

Waldorf have made interaction with external MIDI controllers and modular systems a breeze. Anyone with an MPE controller can integrate it nicely with support for polyphonic X axis, Y axis, and pressure. The expressive playing of Iridium’s synthesis engine is something I found very rewarding, and my ROLI Seaboard Rise worked perfectly when plugged into Iridium’s USB host port.

Modular folks will also appreciate the CV ins and outs, which can be used to play the Iridium (monophonically), supply clock (in or out), and pipe in up to four additional CV signals. All the inputs can be freely assigned in the modulation matrix.

Pros

  • The same exotic synthesis engine as the Quantum.
  • 16 voices is enough for most tasks.
  • Even though it doesn’t have analogue filters like the Quantum, the digital filter choices are plentiful and sound great.
  • True stereo signal path throughout.
  • This is the right synth for polyphonic aftertouch.

Cons

  • Only one stereo output.

Summary

The Iridium is a digital version of the Quantum with all the same intoxicating synthesis options. There are digital filters instead of analogue (which makes sense), double the number of voices, and a new polyphonic aftertouch keyboard. All of which could tip the balance and make this Waldorf’s new flagship extraordinaire.

Information

£2399 including VAT.

www.waldorfmusic.com

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Published September 2022

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