THE FLAT PANEL ALTERNATIVE

Flat-panel loudspeakers from Sound Advance Systems combine invisible aesthetics with omni directional performance.

Throughout the history of audio, loudspeakers utilizing conical, dome-based, or compression driver designs have dominated virtually every segment of the marketplace. Still unknown to many, however, is the fact that there is an alternative to these well-known technologies which has been around for decades, and is currently making a play for a larger market share. Less obtrusive in style and configuration, this alternative product category departs from tradition in that it is based around a flat-panel, or planar design.

Wait a Minute… Flat Loudspeakers?

Within a dome-and-cone world, that may sound like a notion which defies inviolable laws of physics. But it's not. Consider, if you will, that the first truly practical Flat Panel loudspeaker was manufactured 67 years ago in the U.S. by the Automatic Musical Instrument Company of Grand Rapids, Michigan. An electrostatic device used by the company in a coin-operated precursor to the modern juke box, this Flat Panel patriarch performed poorly by today's standards, but worked nonetheless, establishing a path for others to follow.

But others were slow in coming, if they came at all. As time passed, the further refinement of Flat Panel loudspeaker designs was stymied by cost. The materials required in the manufacturing process were simply too expensive to encourage a proper profit incentive. All that changed in the 1960s when the materials required to produce Flat Panel loudspeakers on a large scale became widely available at more reasonable prices. Built using a number of plastics and charged films, flat electrostatic devices appeared in number, among which the most famous was the Quad ESL 63.

But even with the availability of cheaper materials at a manufacturing level, Flat Panel loudspeakers remained the red-headed stepchild of the audio world. Still widely perceived--accurately or not--as esoteric and expensive, their demand on electronics and somewhat unstable nature at the time often made ownership an ordeal about as pleasant as the prospect of a vasectomy performed with a dull linoleum knife.

In the Late '60's Flat Panel Evolution takes a three-way split

Meanwhile, back in the mainstream audio world of the mid-to-late '60s, a wellspring of advancements were made in traditional loudspeaker design such as air suspension and the development of long-throw transducers. At this same time, the evolutionary path taken by Flat Panel loudspeakers diverged into a three-way split.

One group, including manufacturers such as KLH, Martin Logan, and Infinity opted to maintain a conventional high-voltage approach. A second faction, of which Magnapan was representative, decided to seek out ways in which energy could be created using magnetic materials. A third and considerably smaller band of individuals sought to construct Flat Panel systems from other types of materials to produce a reliable, cost-effective product capable of delivering true hi-fi performance.

Enter Dr. Jose Bertagni

Among this latter group was a physics professor named Jose Bertagni. Working in his native Argentina, Bertagni experimented with materials including thin sheets of wood and plastic to produce diaphragms to accompany his omnidirectional Flat Panel loudspeaker designs. Ultimately, he discovered an expanded polystyrene-based formulation composed of individual beads which could be heat-formed into complex shapes while maintaining uniformity in structure and an even density. By 1970, he was granted his first U.S. patent, and subsequently was presented with 22 others in countries around the globe. Since then, 16 more patents have been granted worldwide for other Bertagni designs.

Bertagni began manufacturing his flat-panel loudspeaker designs in Buenos Aires, but by 1975, he moved his operations to the U.S. in Southern California to escape the increasingly hostile Argentinean political climate. Today, the company is based in the Southern California town of Santa Ana, where an engineering team led by Bertagni's sons, Alex and Eduardo, continues to devise new Flat Panel designs (the elder Bertagni died in 1992). Having operated under the names Bertagni Electroacoustic Systems (BES) and Bertagni Electronic Sound Transducers (B.E.S.T.) International for a number of years, the company is currently known as Sound Advance Systems.

While manufacturing under the BES name, the Bertagni family sold their products mainly to high-end consumer audiophiles. Their success with BES Geostatic loudspeakers in this market funded research to develop other applications of their Flat Panel technology, and by 1980, the company had expanded its marketing efforts to include commercial, pro sound, and residential applications.

Flat Panel Units Offer Two Advantages Over Conventional Devices

The advantages of Flat Panel loudspeakers over conventional designs are essentially twofold. First, their flat configuration allows sound to be dispersed from the entire surface of the diaphragm as opposed to just the center. This translates into omni directional performance characteristics which spread sound out evenly across the entire listening environment, not just directly underneath the loudspeaker source.

Secondly, flat-panel transducers can be easily concealed. Within Sound Advance's current product line-up, models are offered which can be installed within a wall or ceiling in a fashion rendering them completely invisible. They can even be painted over or wallpapered. Models designed expressly for distributed overhead systems mimic the size and exact appearance of tiles used in drop ceilings.

How Sound Advance Loudspeakers Work

In a most basic sense, here's how the current generation of Sound Advance Flat Panel loudspeakers work: Instead of propagating sound by passing it through a cone or dome-shaped structure, an electrical signal is sent through a copper-wire coil, which produces a magnetic field causing vibrations. This coil is attached to the back of a specially fabricated diaphragm made of polystyrene. Vibrating back and forth, the diaphragm bends like an archer's bow to produce a wide variety of pitches which vary according to where it's struck by the coil. As previously mentioned, the sound itself then emanates from the entire surface of the diaphragm. When paint or wallpaper is applied over these loudspeakers, it merely becomes part of the vibrating surface.

Within this entire operating scenario, it is important to remember that the diaphragm is what sets this transducer technology apart from all other types of radiating sources. During the manufacturing process, special additives are added to the raw polystyrene bead material used by Sound Advance which enables it to meet ASTM E84 flame-spread and smoke-density ratings. Then the material is formed under heat and pressure via a wet molding process which also provides the shaping needed to create grooves and channels called IM traps which reflect return energy from the diaphragm edges away from the coil.

An environmentally-controlled curing period follows, during which the diaphragm is stretched and bonded to its supporting frame with proper amounts of tension. Dampening weights are added at this point in time as well, at a number of points in each system to tune the motional response of the entire motor structure.

Upon completion of this process, the motor structure houses a variable-thickness diaphragm which rigidly complies to lower frequencies while allowing a carefully-controlled, progressive decoupling of the diaphragm's surface from the driver to reproduce higher frequencies.

Given its very nature, the entire diaphragm assembly radiates energy at lower frequencies while a controlled and tailored reduction in effective diaphragm surface area occurs as the frequency increases. This produces exceptionally wide angular coverage at higher frequencies as a result.

Conversely, low frequencies move the diaphragm backwards and forwards from a central position in a motion dampened completely at the edges. Mid and high frequencies travel from within the composite material toward the outer edges, where they are extinguished inside the IM traps.

Collectively, all of this activity energizes a large number of the individual polystyrene beads comprising the diaphragm's base material. When each bead comes into contact with an adjoining bead, it radiates just like a miniature point source.

Over the years and through the various name changes, the company which is now Sound Advance Systems has seen their Flat Panel loudspeakers installed in the White House, King Fahd's palace in Saudi Arabia, the Greek Theater in Los Angeles, the Mirage Hotel in Las Vegas, the Hard Rock Cafe in New York City, the Hotel de Coronado in San Diego, the Ritz-Carlton in Dana Point, California, the Hollywood Bowl, and private residences of great distinction and celebrity. Privately held, the company is given direction today by President Donald J. Taffi.

Other Manufacturers Involved in Flat Panel Technology

Other manufacturers currently involved in the flat-panel loudspeaker race in the U.K. include New Transducers Limited (NTL) and NCT. Designers of the well-hyped NXT line of components, NTL promises to bring their first flat-panel products to market in the very near future.

As for the future of flat-panel loudspeakers in general, based upon all evidence, the technology has matured to the point where it is here to stay. In addition to the applications described thus far, those imbued with the entrepreneurial spirit are already aglow with an abundance of ideas. Projection TV screens could easily double as a loudspeaker, for instance. Or how about having the headliner of your automobile serve as a loudspeaker system too? Then there's the notebook PC equipped with sound panels that slide out of the sides next to the display screen. And don't forget a talking microwave oven, combination solar-powered toaster/portable stereo, and, well, let's just say the possibilities are endless for now, and leave it at that.