This technology is used in the majority of Zu’s loudspeakers. Its concepts can be used in any loudspeaker where there are internal velocity changes. The technology concept was introduced in Zu’s very first loudspeaker, Druid. The Zu-Griewe technology 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 the late Ron Griewe and Sean Casey. The original concept is Ron Griewe’s, a motorcycle legend that had a nice bit of engineering insight as he sat inching through Los Angeles traffic one afternoon. (More about Ron Griewe below.)
Let’s outline a few basic principles expressed in the technology 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.
Zu-Griewe technology is expressed, on a fundamental level, like that of a waveguide with expanding acoustic cross section and terminated and driven at one end. Propagation within the Zu loudspeaker is mostly planer and standing waves are not as stimulated as in other similarly sized designs. 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. Zu-Griewe can reduce many of these problems.
Applied to loudspeakers, this new technology reduced noise 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. The basic idea however is acoustic impedance matching of the high Z of the cone to the low acoustic Z of the room; the reduction of non-planer propagation in more than just a single octave; the reduction of internal cabinet standing waves.
Ron “Ogre” Griewe 1939–2005
Original concept as applied to exhaust systems for internal combustion reciprocating engines, is the brain child of the late great Ron “Ogre” Griewe—two wheels and a fist full of throttle. Sean had the pleasure of working and riding with Ron back in the nineties at ATK motorcycles.
Ron was a well-known and well-respected character and professional 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, projects 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, a guy that didn’t get his knowledge from a can. For him, leaving Cycle World—a bikers dream job, getting payed 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 when Ron and Sean tore it up together and only a season long, but Sean will never forget the time spent riding, talking and working with him. Ron turned seventy the month before Sean returned to audio; Ron was one fast mother, forget about age. Seriously fast, technical single track or super fast fire road. Riding the desserts of Southern California? Hit the Husky Monument.