Genesis Technologies Genesis III loudspeaker
The new Genesis III loudspeaker shows just how sophisticated the designer's art has become. The Genesis III is as far removed from the cones-in-boxes loudspeakers of yesterday as a Ford Taurus is from a Pinto. Combining a radically different cabinet with unusual custom drive-units, the Genesis III is a paradigm of how high technology has transformed loudspeaker design.
This discussion is particularly relevant to the Genesis III because it was designed by Arnie Nudell, who quit his job as an aerospace physicist 25 years ago to start a loudspeaker company, Infinity, in his garage. Arnie has thus witnessed firsthand the radical transformation of loudspeaker technology, and, indeed, has been one of the driving forces behind it.
After leaving Infinity in 1989, Arnie joined forces with PS Audio founder Paul McGowan to form Genesis Technologies. The Colorado-based company produces a line of loudspeakers ranging from the $499 Genre I (which I thought was the bargain of the 1993 WCES) to the ambitious $50,000 Genesis I, unveiled at the Chicago SCES in June. The Genesis III is the top-of-the-line modelnot counting the Genesis I.
The Genesis III is a five-way design using two woofers, two dome midranges, and the Genesis 1" circular planar-ribbon tweeter. The drivers are mounted in a 53"-tall sealed cabinet that's unlike any previous loudspeaker enclosure. The Genesis III's unusual cabinet plays a large role in the system's design goals. Rather than comprising an assemblage of flat panels, the III's enclosure is made from wood fiber wound in thin sheets around a form. This technique allows Genesis to make the 1"-thick enclosure any shape it wants. The company has exploited this unique potential to create a very sophisticated enclosure.
The cylindrical cabinet has a flat front baffle and gradually flared sides near the tweeter. The baffle is 2"-thick MDF. The area on either side of the baffle is gradually flared, with the greatest flare near the tweeter at the top of the enclosureto reduce diffraction. The enclosure is tilted back at an optimal angle for time coherence, and the rounding of the enclosure eliminates standing waves inside the cabinet that could contribute to resonances. A layer of damping material lines the inner walls, further reducing cabinet resonance. Genesis claims that the III's cabinet is more inert than an enclosure made from 4"-thick concrete walls.
The long, narrow grille is made from black fabric stretched over a welded tubular-steel frame. Despite the low diffraction from this frame design, Genesis recommends listening with the grille off. All my auditioning was performed sans grilles. A layer of neoprene rubber covers the front baffle to further reduce diffraction effects.
My review samples were finished in piano-black lacquer; rosewood is available for $200 more. The Genesis III's look, build quality, and fit'n'finish are all exemplary. The impressive cabinet finish wouldn't look out of place with fine furniture.
Two pairs of input terminals are provided for bi-wiring. The terminals are gold-plated solid brass, and use a brass nut for tightening instead of the plastic-covered nut found on five-way binding posts. Three level controls appear on the back panel just above the input posts. These adjust the relative output levels of the tweeter, upper-midrange, and lower-midrange drivers, respectively.
The Genesis III's two woofers are wired in parallel, with the lower woofer rolling off above 70Hz. The upper woofer is run up to 250Hz, where it crosses over to the lower midrange unit. The lower-midrange dome driver reproduces frequencies up to 850Hz, the upper-midrange dome driver handling the spectrum to 4.2kHz, where the ribbon tweeter takes over.
A five-way design is unusual in the High End, most loudspeaker designers choosing the classic three-way configuration. Nudell, however, makes a good case for a five-way loudspeaker, arguing that it tends to maintain constant dispersion with frequency. With each driver used in a relatively narrow frequency range where its diaphragm is smaller than the wavelengths of sound it produces, there is no abrupt change in radiation pattern as one driver rolls off and a smaller one takes over.
As mentioned, the user can adjust the relative levels of the tweeter and the midrange drivers with three rear-panel knobs. Genesis calls these adjustments "room trim," reflecting its belief that loudspeakers should have some degree of adjustment to match them to the room and playback system. Unlike the adjustments on some loudspeakers, the III's controls are sensible and practical. Their range is narrow enough that tonal balance isn't grossly distorted at the minimum and maximum settings. This narrow range also makes fine adjustments easier.
The drivers were all designed from scratch by Nudell. The woofers are a three-layer, metal-cone type. The inner layer is a damping material sandwiched between two aluminum layers. Nudell says this configuration provides great stiffness and low mass. The woofer's first break-up mode is said to lie at 7kHz, far above its passband.
The midrange units are unusual in several respects. First, they are domes rather than cones, which is claimed to confer several advantages. Because a dome is driven by a voice-coil surrounding its outer edge, its operation can be more linear. Applying a uniform pressure to the diaphragm's circumference results in the diaphragm acting more like a perfect piston. This is contrasted with a cone driver driven by a voice-coil at the cone's center, where the diaphragm can tend to flex more. In addition, for the same sized diaphragm, a dome driver can have a larger voice-coil than a cone unit. This increases power handling and reduces dynamic compressionthe flattening of dynamic peaks caused by voice-coil heating.
The dome diaphragms are extremely low mass, being made of titanium silicon carbide, a very light and rigid material. Moreover, the diaphragms are very thin, measuring just 0.003" thick, about the same as a human hair. In fact, the Genesis midrange diaphragm is as light per unit area as that of most titanium-dome tweeters.
As unusual as the woofer and midrange are, the tweeter is perhaps the most innovative of the Genesis III's drivers. Although the same size and shape as a conventional dome tweeter, it is actually a small ribbon transducer. High-frequency ribbon drivers are typically long and thin, characteristics that make unusual demands on the enclosure and driver arrangement. The most pressing of these demands is the difficulty of mating a line source (the long, thin ribbon) with a point source (the dynamic woofer). Because the Genesis ribbon is small (1" in diameter) and round, it has a similar point-source radiation pattern as the other drivers with which it must integrate. A round diaphragm also has the same dispersion pattern in the vertical and horizontal planes. These qualities greatly simplify using a ribbon in a dynamic, multi-way loudspeaker.
The tweeter's diaphragm is an extraordinarily thin layer of Kapton. The 2.5µm-thick diaphragm is so light that, up to 40kHz, it has less effective mass than the air in front of it. The diaphragm has a spiral voice-coil attached to it that is suspended in a strong magnetic field. The tweeter's structure necessitates placing the voice-coil in a weaker part of that field, but is still strong enough to provide high sensitivity. Indeed, the tweeter level is padded down in the Genesis III.
The crossover uses many elements, but very few of them are in series with the drivers. As would be expected from a five-way loudspeaker, the crossover is extensive, occupying two boards. The crossover slopes vary between second-order (12dB/octave) and third-order (18dB/octave), with increments in between. None of the slopes are first- or fourth-order. All the drivers are capacitively coupled, making the Genesis III immune to DC. (A special foil/polypropylene capacitor was custom-made for the III's tweeter circuit.) The woofer circuit has an LC network (a series capacitor and a shunt inductor) to increase the sealed-box enclosure's LF extension and tame the large impedance bump at the enclosure tuning frequency. Genesis claims that this technique increases the amplifier's control over the woofer: Cone movement is controlled by the amplifier, not by the box resonance. The inductor is a huge 5-lb device, and the capacitor's value is a whopping 1000µF. These factors, along with the five drive-units, suggest that the III has high power-handling ability.