How We Manufacture Our Marble Enclosures

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Proof that thinking outside the box really works

How liquid composite becomes solid Q-Stone™ shaped for sound.

Eos_faceplate Roy Johnson has incorporated cast marble in each of his speaker designs since 1991. A result of 15 years of research and experiments, the process of casting our proprietary Q-Stone™ cast marble is an outcome of each model's research and development phase. Before the first drop of cast marble is poured, wood masters and rubber molds are produced.

For each piece of marble that we cast, Johnson shapes a 'master' out of wood and includes any guides that will later be drilled for screws. He then coats the wood master with several layers of black primer. For example, the Eos faceplate wood master (above), is one of five unique wood masters for that model.

Each wood master is slightly larger than the final piece of marble since the Q-Stone™ mixture will shrink as it cures -- a factor Johnson calculated in the speaker's development phase. He also previously determined the amount of flexibility needed in each silicone rubber mold and the shapes of any wood plugs that may be required, as well as any needed 'plugs within plugs.'

Liquid_rubber After the appropriate custom box is constructed, the interior is coated with petroleum jelly. By this time, the rubber and catalyst mixtures are ready to be mixed and then poured into their respective boxes (left; stains on the wood are petroleum jelly). The color of the rubber denotes its stiffness properties. Through the years we have used white, blue, green, and most recently, pink. In a humid environment, the rubber would harden fairly quickly; however, we allow it to cure over several days to compensate for the dry air at our elevation.

Because the rubber is poured in the reverse (upside down), the resulting mold is turned right side up once the mixture has cured. The smaller rubber molds will be removed from their custom boxes, while the larger molds will need the wood box's stability during their service life. Each resulting mold will have a service life of about five years.

Our rubber molds may look 'low-tech,' yet the interior shapes permitted by the molding process will reduce internal standing waves in the resulting speakers and the external curvatures will prevent reflections.

Marble_dustTo make the cast marble, a unique mixture of polyester resin, ultra-fine, pure marble dust (left), and a black powder is blended. Two different catalysts are then added -- one cures quickly and the other requires several hours to harden. At this point, the cast marble mixture has a consistency of pancake batter.

Raw_marble The mixture is then poured into clean and perfectly level rubber molds. The catalysts cause the marble to become very hot before it shrinks away from the sides of the molds as it cools to room temperature. Johnson calculated this shrinkage during the prototype and wood mastering stages of the model's development process.

After the cast marble pieces have cured, they are removed from their rubber molds and hand-finished through several steps of wet and dry sanding. Once all the pieces are smooth, some are fitted together, as with the cabinets for the Eos and Eos HD models. Later, all will be primed and then painted with our Texture-Kote™ paint and will look and feel like pin-grained leather when dry.

Photos: The research and development phase is a series of many processes that result in the production of wood masters for each piece of cast marble as required by a particular speaker design. For example, five different pieces of cast marble comprise the Eos and Eos HD cabinet. The front faceplate wood master, shown, has received many coats of black primer and been carefully polished. It will be placed face-up in a custom-made wood box and have rubber poured over it. In another photo, the pink rubber compound being poured is the pink center 'plug' seen in the photo at the top of the page. The liquid cast marble being poured into the light green mold will become the outside shell of the Eos and Eos HD cabinet.