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What is ZuRG loudspeaker technology This technology is used in many of our loudspeakers and its concepts can be used in any loudspeaker where there are internal velocity changes. The technology was introduced in our very first loudspeaker, Druid. ZuRG is a multi-octave impedance modifying acoustic model that can be applied to any acoustic system with alternating velocities; electro-acoustic, electromechanical, internal combustion engines, and so on. It is developed exclusively by Sean Casey, the late Ron Griewe, and Adam Decaria. Models are kept as trade secrets (we ain’t talking to much about the how to’s, at least not today). The original concept is Ron Griewe’s, a motorcycle freak that had a nice bit of engineering insight as he sat inching through Los Angeles traffic one afternoon. More about Ron below.So, let me outline a few basic principles expressed in the Druid and contrast them with bass reflex (ported) designs as well as transmission lines, pipes and horns. A bass reflex loudspeaker uses a simple Helmoltz resonator to augment lower frequencies via the air “spring” in the cabinet and the “mass” in the port, tuned to add amplitude response, and control cone motion. A Helmoltz resonator consists of a rigid-walled cavity (the volume) with a neck (“port”) with an area and length. The fluid (air) moves as a unit within the port tube to provide the mass element and the acoustic pressure within the loudspeaker box provides the stiffness or spring element; the resistive element is provided by the opening that radiates the simple source sound. All Helmoltz resonators contain these basic elements, and all create sinusoidal waveforms but cannot recreate the complex and dynamic waveforms typical of music. The Druid enclosure is expressed, on a fundamental level, like that of a waveguide with uniform or expanding cross section and terminated and driven at one end. Propagation within the Druid is mostly planer and standing waves are not stimulated. Power radiation from the open end is expressed similarly to that of a standard open-ended pipe, driven and terminated from the opposing end. Though similar, the Druid cannot be defined by waveguide, transmission line, or driven pipe models. Development of acoustic models accounting for driver introduced dynamic variables within horns, pipes, and transmission lines revealed areas of non-planer propagation. This turbulence (noise) is wavelength relational and proportional to amplitude. ZuRG can reduce many of these problems. Applied to loudspeakers, this new technology reduced noise distortions, in varying degrees, over the majority of the audible bandwidth. These new ideas in acoustic impedance transform function, and the designs they realize are proprietary; or rather, we really don’t care to tell you how to do it, not yet anyway. The basic idea however is the reduction of non-planer propagation in more than just a single octave. Original concept as applied to exhaust systems for internal combustion reciprocating engines, is the brainchild of the late great Ron “Ogre” Griewe—two wheels and a fist full of throttle. Sean had the pleasure of working with Ron back in the mid nineties at ATK motorcycles. Upon hearing the basic idea, Sean immediately recognized its application to acoustics, specifically loudspeakers. Five years later Druid was born, Zu’s first loudspeaker. Ron was a well-known and well-respected character in the motorcycle world. Known in his younger days for desert racing, always running a bit too close to the edge, but always with a grin and a cigar. Later, Ron made a significant contribution to bikers, street and dirt, in his writings and leadership at Cycle World magazine. While there he rose to Editor-In-Chief, a position he held for 16 years. But the Ron Sean knew was really an inventor and engineer, not classically trained but his intuition and experience made up for any lack of formal engineering training. So learning that he left the ideal bikers job, getting paid to ride all kinds of bikes all over the globe, to drag ATK America out of custom one-off dirtbikes shop and into a real production based American made dirtbike factory, made perfect sense. Yeah, it was a while back that Ron and Sean used to ride together, and only a season long, but Sean will never forget the time spent riding and working with him. Ron turned seventy the month before Sean returned to audio; Ron was one fast mother, forget about age. |