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WMD Crucible

Eurorack Module By Rory Dow
Published November 2019

If you want to build your own drum machine the modular ecosystem is the place to be these days. The wealth of drum modules available now means you can pick and choose your drum components, add as many as you like, add sequencing, effects... the world is your oyster. The WMD Crucible is here to add complex cymbal synthesis to the list of tempting drum voices.

WMD Crucible. Size: 8HP. Current: +12V 63mA, -12V 17mA.WMD Crucible. Size: 8HP. Current: +12V 63mA, -12V 17mA.The Crucible is described as a ‘curved metal and cymbal synthesizer’ and although it is entirely digital, the sound may have you believing otherwise. The Crucible’s aim is to create realistic cymbal sounds, and they do mean acoustic cymbals. This is quite a claim. Most synthesized drum machines don’t get close to realistic cymbal sounds (but we love them anyway, right?). In fact, cymbals are so tricky to synthesize that many drum machines will resort to using samples, even when the other non-cymbal sounds are purely synthesized. Rest assured, however, there are no samples here.

The Crucible is 8HP, which is quite large for a dedicated drum module, but it packs in many more parameters to tweak than the average, and is more flexible than most cymbal modules I’ve come across. There’s also an impressive amount of connectivity.

The synthesis engine can switch between three different models: Cymbal, Cracked Cymbal and Curved Plate. All three make use of the same six parameters: size, pitch, decay, tone, excite and deform. Size, pitch, decay and tone are self-explanatory. Excite is a way to change the stick material and strike method. This primarily affects the transient of the sound, but can also have an effect on the resulting decay. Deform actually changes the thickness of the cymbal, with thinner cymbals making a more splashy sound.

Triggering the cymbal can be done using either the handy trigger button, or using either the Edge or Mid trigger inputs. A red LED will illuminate briefly for each trigger and decay at the same rate as the audio. The two trigger input options do a great job of emulating hitting a cymbal either at the edge or in the middle, which results in a different timbre, with edge being more splashy and mid being more ‘tingy’. It’s not obvious from looking at the front panel, but if you hit both inputs simultaneously you get a third hit type, a bell emulation, resulting in a more ride cymbal-type sound. There’s also velocity input, to which you can feed a CV amount to control the strength of the strike, which also affects the physical modelling engine.

All of this makes the Crucible one of the best physical-modelling cymbal engines that I have come across, not only in modular-land, but anywhere.

A choke input allows you to emulate the choking of a cymbal using a gate input. The longer the gate, the more drastic the choking effect. By sending shorter gates you can effectively mimic quick grabs of the cymbal which don’t fully mute the decaying sound but just dampen it slightly. This is an interesting input to combine with sequencing and clocks for rhythmic effects.

There is a final input jack that isn’t something you’d expect on a drum module. This audio input allows you to use any signal as an exciter to the cymbal engine. This is, in my furtive imagination at least, somewhat akin to screaming so loudly at a cymbal that it starts to resonate on its own. The results range from everlasting cymbal washes to almost comb filter-like drone effects.

The Crucible sounds excellent. The range of cymbal sounds is substantial. It can cover crash cymbals, ride cymbals, open and closed hi-hats and many types of metallic percussion. The synthesis engine is impressive. No VCAs are used. Cymbal decay is a natural by-product of the physical modelling and sounds can decay over minutes, if so desired. As well as delivering extremely realistic cymbal sounds, the engine also gives you the opportunity to push parameters into unrealistic territory, resulting in the weird and wonderful. I did notice, at some settings, a tendency for high-pitched fundamental frequencies to be rather too dominant, causing piercing high-frequency sine waves to stand out, but some gentle massaging of the parameters generally mitigated the problem. It’s not just for realistic cymbals either. At certain settings, analogue-sounding hi-hats and cymbals are also possible.

All of this makes the Crucible one of the best physical-modelling cymbal engines that I have come across, not only in modular-land, but anywhere. The range of sounds is huge, and with extensive CV control and the external input to excite the engine, the potential for interesting and unusual sounds is splendid. If you’re a fan of drum synthesis, I urge you to check it out.