Crystal Speakers

The ongoing project known loosely as Crystal Speakers, has been an exploration into various electrical and acoustic properties found in the environment. In an attempt to create audio circuits from scratch, I zeroed in on the central part of any amplified sound system - the speaker. Although most commercial speakers are highly engineered (and endlessly praised for being so), the speaker mechanism is quite simple and can be replicated from basic ingredients.

My aim was to express sound (or at least energy) through earth-like materials, in order to contrast the atmospheric signal to be played through them. Knowing the piezoelectric properties of quartz, I decided against the standard electromechanical speaker design, and set out to turn piezoelectric rocks into handmade speakers.

Process

This work is heavily processed based. Firstly it involved searching for quartz in the environment, as well as making piezoelectric Rochelle salts crystals from scratch.

Cooking the Rochelle salts involves a mixture of sodium carbonate and potassium bitartrate. The recipe can be found here. However, this process is not as simple as just following the instructions. The highly volatile preparation depends on timing, consistent cooking temperature, filtering, humidity, room temperature, and numerous other variations. In short, creating a strong, good-sized, and highly piezoelectric crystal to use as a speaker involved uncountable preparations with fine attention to detail. Many times a two hour cooking session will yield only crumbs due to a slight drop in cooking temperature or a compromised filtering process. A "crystal cooking diary" has been kept in an attempt to replicate results -- still, some elements (especially environmental ones) prove difficult to control every time.

Once the crystals were ready, each needed to be tested for their individual piezoelectric properties. Using an oscilloscope the crystals were subject to pressure tests to obtain their voltage output (peak-to-peak). The results ranged from less than 1 volt on the smaller crystals, to over 40 volts on the large crystals. 

Quartz crystals found locally were also tested for their piezoelectric properties with moderately good results. As I progressed through to speaker testing, they unfortunately couldn't compete with the volume and response of the homemade Rochelle salt crystals. I'm hoping to include found quartz in later iterations or other related projects.

Finally, the chosen crystals were ready to be put in circuit.

Using aluminum foil as both the electrode and speaker diaphragm worked surprisingly well. It is both conductive, malleable, and thin enough to carry the tiny vibration from the rock. However the rough looking test-bench design needed to be streamlined for exhibition.

After much deliberation I replaced the foil with copper shim, as it maintained similar properties of conductivity and acoustic resonance but without the mess. Additionally, it was rigid and could be shaped to accommodate various designs. The copper changed the tone quality of speakers dramatically, giving them a distinctive metallic, ringing mid-tone - in contrast to the crisp, high-end crackle of the aluminum foil.

The vice and makeshift clamps were replaced by clear polycarbonate stands. The stands needed to be able to hold the rock securely and maintain firm pressure from both sides. Without this constant pressure, the vibrations of the rock would not couple to the diaphragm efficiently enough to produce an audible volume. These stands had to be custom designed and made.

Finally, the two electrode/diaphragms on either side of the crystal had to be carefully isolated from each other to avoid shorting, and - most importantly - so they could not be touched at the same time. Due to the high voltage, If contact was made across the two electrodes a decent electrical shock was felt (around 800V ac, low current).

Initially I'd imagined wiring up half a dozen or more crystals into an array of speakers. In theory, the load drawn by more crystals would reduce the impedance on the transformer, making the crystals louder. In practice however I noticed no audible difference, and due to the mess of wires involved preferred the minimal appearance of only one or two large crystals.

Exhibitions

The first iteration of the crystal speakers was exhibited at 55 Sydenham Rd in December 2015. Titled Lithosferics, two large Rochelle salt crystals drove large copper diaphragms, resulting in a strange, homemade concoction of earthen minerals chirping with sounds originating from lightning strikes on the other side of the planet.

These works were part of an integrated sound installation with two fellow artists, Nathan Thompson and Peter Blamey. The exhibition, titled In Fields created an otherworldly soundscape from the electrification and subsequent interaction of unconventional objects and materials.

In 2017 another design of the Crystal Speakers were exhibited, this time alongside another work, Batteries. New crystals were developed and the large copper shim diaphragm was replaced by a small (hidden) aluminium sheet sandwiched between two copper shim tabs, protruding a few centimetres below the clamp. The combination of aluminium and copper created a broader and more complex set of audio frequencies.