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Waldorf Iridium Keyboard

Synthesizer By Rory Dow
Published September 2022

Waldorf Iridium Keyboard

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.

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