The Big Review: Waldorf Iridium

As Waldorf adds to the periodic table, we take a quantum leap into this next-generation desktop unit to see if its power is as dense as its namesake

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Waldorf Iridium

Price £2,000
Contact Waldorf

Rising from the ashes of PPG – long acknowledged as the company that brought wavetable synthesis to the masses through the development of its early wave synths – Waldorf has always held a unique position in the industry. Many attempts have been made to bring this kind of wavetable technology back to the fore but it was Waldorf’s Quantum that best updated the PPG Wave for the modern age. Bedecked with a touchscreen and onboard pots, the Quantum strengthened the argument for wavetable as a unique and creative sound source packaged in a hands-on format. But while it deserves its flagship reputation, it comes with a flagship price.

Quantum leap

Wisely, Waldorf always sought to place the Quantum in a desktop box, which in essence is what the Iridium is: a desktop synth. Waldorf has, however, made some slight alterations that might have Quantum owners pondering a switch.The Iridium is designed to fit on your desk, in essentially the same case that houses the Waldorf Kyra. It’s not small but it packs a lot of functionality, and anything smaller would clearly result in a loss of control. It’s also fairly heavy at 5.4kg, important if you’re considering mounting the module using the VESA mounting holes on its underside. This could give the Iridium a fantastic floating quality in the studio but you’ll need a firm bracket. The weight is a testament to its build quality. Its pots, metallic fascia and chassis are robust, and the touchscreen is crisp, even if it occasionally feels unresponsive, depending on how much information is on display.

As there’s no musical keybed, you can make use of the conventional MIDI socket connectivity or USB MIDI. There’s no audio over USB but there is a stereo in and out, using quarter-inch mono jacks. There’s also provision for connecting up Eurorack equipment, with four CV inputs, as well as gate and clock input. Like the Quantum, there’s also a SD card slot, useful for loading user samples and wavetables.

Apart from these desktop-version differences, there are two more major changes from the Quantum. Firstly, the voice count has been increased to 16. The second big switch is the removal of the analogue filter element, which has been replaced with a digital facsimile. This arguably takes the Iridium away from its PPG roots, where digital oscillators have always been used alongside analogue filters. But there’s nothing to fear here. The Iridium exploits the latest software release, 2.0, which offers a host of new capabilities, not least a new oscillator voice mode.
Waldorf Iridium

Making WAVES

The Iridium’s three oscillators are identical. Each offers five wave modes, which are selected using four buttons that illuminate when pressed. The new kernels-based synth mode requires a two-button press, which is clearly labelled on the front panel.
While the Iridium conforms to the structure of many subtractive synthesisers, the oscillators are a rich resource. You can get lost for hours after simply activating a single oscillator and placing it in the first synthesis mode, Wavetable. Each oscillator has five pots, with labelled legends for each mode, aiding experimentation. These interact alongside six pots aligned in threes on either side of the touchscreen. You find your level while sculpting sounds but it’s helpful to have options for working with pots and/or touch, as the pots offer greater numeric accuracy in many cases.

Within Wavetable mode, it’s easy to create textures with the Waldorf-supplied wavetables. If you want to go further, the SD card slot provides an easy route to importing your own wavetable creations.

You may find the layout cramped but that’s only because Waldorf has put everything on parade

The ability to activate a second oscillator in the conventional subtractive Waveform mode provides an easy path to adding a supportive fundamental to your wavetable. Each oscillator has a Coarse and Fine pot, so creating sub-oscillators is easy. Kernels are available in Waveform mode now too, which means it’s possible to apply up to six oscillators to a wave. In the case of Waveform mode, this means you can create über-thick Euro-style voices thanks to the ability to detune subtly or with more aggression. The control is not purely limited to this though. Entire chords can be created in this mode, while only occupying a single voice.

The Particle mode opens up the possibility of sample imports, either for the purposes of straight sample playback or as a source for granular synthesis. Like the Wavetable mode, this rabbit hole is deep and richly rewarding. Samples can be loaded via the SD card slot and, while it could be argued that merely using the Iridium as a sampler is a waste, importing samples for the construct of a multi-zoned instrument can be laborious. There’s an absence of batch-loading and formatting here though. But once you’re lost in the granular frenzy of Particle mode, you probably won’t mind.

Waldorf Iridium

Layers upon layers

The Resonator mode boasts crisp and percussive resonating tones, perfect for fronting more pad-like patches. But it’s the new Kernel mode that really adds a further layer to the oscillator. The Kernel mode comes with 14 templates, providing a solid launchpad. Apart from the more commonplace addition of sub-voices for detuning, there’s a host of Frequency (FM) and Audio rate (AM) modulations possible here too.

There’s a Pandora’s box of audio complexity to be found here, moving from gentle to aggro very quickly, and all with an incredible degree of control and sophistication. Much of this is modelled on the concept of traditional FM synthesis, developed by Yamaha for its DX synths. But where we used to have to play key-hole surgery with the DX7, the Iridium’s display and extensive modulation options makes light work of such a complex synth mode.
Novices will never find FM synthesis as easy to understand as subtractive synthesis. But large touchscreen displays certainly help. The templates provide handy building blocks to get you underway too. Moving into Edit mode sees the display mimicking the algorithms of the DX synths, which aids experimentation, especially if your understanding of FM is lacking.

Drawing breath at this point, the experience of working with the oscillator section is both clever and rewarding. If you’re used to the Quantum, you might find the pot layout cramped. But that’s only because Waldorf has tried to put everything on parade here.

Waldorf Iridium

Stereo, stereo

All three of the Iridium’s oscillators are summed into a mixer, which feeds the filter section, with the comprehensive routing screen allowing you to dictate the signal flow easily. As a consequence, oscillators can feed specific filters or bypass them altogether. This can be exceptionally useful and can help to leave more complex wave content untouched by filters.

Another small difference between the Iridium and its larger keyboard-based sibling is the absence of LEDs next to the level pots in the mixer section, which have always proven useful for confirming signals and indicating which oscillators are in play.

The filter section consists of three separate filters, the first two of which are joined in a dual configuration. As mentioned, these are digital incarnations – but you’d never know it. We’re intimately familiar with the sound of the Quantum, so it came as something of a surprise to discover that the Iridium had switched to digital. Regardless, Iridium offers a variety of filter models from 12dB to 24dB, with clean, dirty or saturated colourations. They always remain in low-pass mode with resonance. Due to their dual nature, there are also shortcuts to allow either linked or independent operation.

The new second oscillator is a behemoth, having supercharged an already powerful oscillator

The third filter is described as the Digital Former. Apart from offering a multitude
of states, from low-pass and high-pass to notch and band-pass, there are numerous varieties here that have been modelled on those from the Waldorf catalogue. You’ll find PPG, Largo and Nave models alongside comb filters, bit-crushers and more. It’s a shame that these could not be shared with the other filters though, which, being purely low-pass, would provide even greater flexibility.

Signal flow remains in stereo throughout this section. If you’re using samples or granular functionality in Particle mode, you’ll likely find this incredibly effective, as the original sampled stereo spectrum is able to remains intact.

Waldorf Iridium

Getting Komplex

Unsurprisingly, the modulation possibilities for the Iridium are vast. It has six envelopes, the first three being assigned to the two filters and the amplifier. Changing any of the ADSR parameters takes you straight to the envelope page, so you can see the progress of envelope travel with the activation of any note.

The Iridium also boasts six LFOs, which direct the user straight to the screen with any movement of an LFO pot. Due to the lack of panel space, there’s some inevitable doubling up of pots. But Waldorf has engineered this unit so that it’s easy to access your desired envelope or LFO through appropriate button selection.

Application of any modulation via the modulation matrix is easy. With 40 slots available for routing, it’s a simple process of selecting the modulation source, followed by its destination, with the amount dialled in as either a positive or negative value. Apart from allowing pretty much any parameter to be controlled from a plentiful supply of modulation sources, it’s here that you’ll also find access to the four CV inputs. If the internal LFOs aren’t to your taste, you can always opt to use a piece of Eurorack or another device equipped with a CV output to provide your modulation needs.

You could also model your own LFO or envelope via the Komplex Modulator. Think of this as a one-stop shop for drawing your own single-shot or loopable modulation waveforms. It’s as simple as selecting the modulator and drawing on screen.

Waldorf Iridium

Element of discovery

Waldorf has added 16 pads to the Iridium that offer a simple way to play notes and, thanks to the shortcut buttons nearby, it’s easy to assign these pads to different notes or scales. They can also be employed to play different types of chords. This can be useful if you want to play an arpeggiated pattern using the Iridium’s arpeggiator or sequencer, the latter of which can be programmed to form a pattern of up to 30 steps. The pads are not velocity-sensitive, which is a shame given the overwhelming quality of the Iridium overall.

Waldorf Iridium


The Iridium is yet another example of fine work from Waldorf. It’s a beautifully put together unit, and an enticing creative powerhouse for anyone who relishes the idea of working with hardware synthesisers. The panel feels a little busy but we’d rather have all elements present than not. The new second oscillator is a behemoth too, having supercharged an already powerful one and issued it plenty of new features.

From its gentle pads to its fascinating wavetables and rip-your-head-off syncs, the Iridium sounds like a full-on professional synthesiser too. The backend effects are equally classy, rounding off a familiar signal path that offers an astonishing amount of sonic content. It’s an ideal unit for anyone with a smaller studio – though it will eat up a chunk of desk space. Once you start to engage with the Iridium on a creative level though, you’ll understand why the sacrifice was worth it.

Do I really need this?

Waldorf Iridium
The pleasure you’ll get from using the Iridium comes via its ability to provide superb sounds very quickly. They may come intentionally or as you stumble across its tools.
It’s brimming with presets but the real joy comes in initialising patches and getting lost in their palettes. If you have a fondness for wavetable synthesis, you’ll find this new desktop unit very special indeed.

Key Features

  • Powerful desktop synth
  • New OS2.0 software
  • Hands-on interface, with touchscreen and pots
  • Three oscillators, with five wave engines
  • Three digital filters, selectable between modelled filter types
  • Vast modulation possibilities, including Komplex Modulator, six LFOs and six envelopes
  • On-board assignable pads, for playing and sequencing
  • USB, MIDI, Audio and CV/Gate connectivity, with SD card slot
  • 85 x 440 x 305mm


Ashun Sound Machines
Hydrasynth Desktop £780

The first offering from new synth brand Ashun Sound Machines made quite an impact. It’s capable of complex waves, coupled with flexible filtering, and
is a fantastic alternative to the Iridium.

UDO Audio
Super 6 £2,200

Another new synth, albeit in keyboard form, the Super 6 features digital oscillators up front with the ability to control basic wavetable waveforms. Its binaural operation results in a true stereo spectrum.


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