Green Mountain Audio

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  • Green Mountain Audio
  • 111 S. 28th Street, Colorado Springs CO 80904, USA
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Green Mountain Audio manufactures or has manufactured the following equipment (click to expand models list):

Dynamic Speakers

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Green Mountain Audio web site (Febuary 17, 2010): Curiosity, passion, determination With no degree for loudspeaker design offered anywhere on Earth -- (and there still is not) -- Roy Johnson had to carve his own path of learning. Here is how he did it. By Janet Lynn.

Early inspirations...and turning points

Wanting better sound than his clock-radio could provide, Roy Johnson built his first pair of speakers in 1968, at age 14. "When I heard Hendrix, B.B. King, and Cream for the first time on a local underground FM radio station a year earlier, I wanted better sound," he recalled. "I could not afford factory-built speakers, so I bought all the raw parts and built a pair for myself. They were a lot better than the clock-radio. I was thrilled."

He wanted more. "I decided surround sound was the way to go and wanted to hide the speakers," he said with a chuckle. "My folks were not happy that I cut holes in my bedroom walls." The following summer, he received a pair of used Electro-Voice Regency speakers from his grandfather. "The sound was dynamic and clear, with great bass," he remembered. "I bought a lot of music."

Shortly after earning his driver's license a few months later, the teenager drove 20 minutes from his family's home in Green Mountain Falls, Colorado, to Colorado Springs to see what was new at the local stereo store. "I passed in front of a Fisher bookshelf speaker that was playing music from a local FM classical radio station," he recalled. "For the first time, I heard the concert hall's echo. It never occurred to me that I could hear reality from a box. It was as if there was an alternate universe. I did not know such a thing was possible, this reproduction of spatial information. In that instant, I became curious about the time-domain. Only later did I learn that the speaker had a first-order crossover."

By age 19, the young man had two years of college math under his belt but left Adams State College in Alamosa to build oscilloscopes for Hewlett-Packard (HP) back in Colorado Springs. The company trained him as an industrial glass blower and in ultra-high vacuum systems, cryogenics, and clean room principles.

Johnson used his income to buy stereo gear and a motorcycle. "I bought my first high-performance stereo components," he said. "I had a Phase Linear 400 amplifier, an ACE Audio preamplifier, a Connoisseur turntable with ADC's XLM phono cartridge, and a pair of Koss electrostatic headphones." He also purchased a pair of speakers from a local store that specialized in high-performance stereo equipment. They featured first-order crossovers and had been built by his colleagues at HP.

After learning that he was interested in speaker design, those same colleagues later handed a box to Johnson. "They told me, 'if you really want to make a better speaker, understand and master all of this first,'" he recalled. Inside the box, Johnson discovered, were papers dated from the 1930s to the early 1970s. "All the research papers that had been published in the Audio Engineering Society's Journal were in there, too," he recalled. "Receiving that box of papers was a major turning point for me."

The beginning of a lifetime of research

As Johnson studied the material, he discovered much of it focused on cabinet reflections and their effects on the sound. He was disappointed that no solutions were presented. By then, Richard Heyser's research had been published by the Audio Engineering Society.

Heyser, a physicist, was respected for his work in sound and acoustics. "He was the first to show the complicated mathematics behind the time-coherent speaker design, how to make meaningful measurements, and ultimately the importance of maintaining a signal, uncorrupted in the time-domain," Johnson said. "At that point, I felt like I had enough information to begin developing my own designs."

He sketched very slender cabinets that held the woofer, midrange, and tweeter in the correct physical positions and also reduced most cabinet reflections. For one of his designs, Johnson contracted with a local cabinetmaker to build new cabinets for his HP colleagues' drivers. "I then worked for a decade with those speakers," he remembered. One experiment involved moving the drivers back and forth, a breakthrough he would later coin "Soundfield Convergence" and incorporate into his designs.

The outboard crossover circuits were also fodder for his experiments. "By then, I had purchased my first spectrum analyzer and measurement microphone," he recalled. "Finally, I could make detailed measurements and correlate them to what I was hearing. The Type 4732 (above) was a direct descendant of those cabinets."

Curiosity leads to the audio industry

Meanwhile, the young designer observed the massive layoffs in the aerospace industry that occurred after NASA's successful space missions to the moon. "I was intrigued at how some engineers from Boeing and other firms had begun their own audio manufacturing companies, like Phase Linear," Johnson said. "Witnessing that shift inspired me to work in the audio industry."

At age 22, he left HP to manage a new stereo store dedicated to high-performance gear in Colorado Springs. "We imported several foreign brands, such as Micro-Seiki (left)" he reflected, in describing the brands beginning to find their way into the U.S. market. "We carried the most cutting-edge components available. It was fascinating to learn from their designers how they conducted their research and how all their work was based on fundamental scientific principles. This was reassuring, since it was the same approach I had used since building my first pair of speakers." Johnson also designed and installed high-powered, disco sound systems for the store's commercial clients.

A friend's request soon opened a new chapter in the designer's life. "He asked me to manage an industrial woodworking plant," Johnson remembered. "While there, I apprenticed under Master woodworkers on machinery normally unavailable to typical woodworking shops."

The designer also managed an audio manufacturing firm before moving to an old mountain lodge in Green Mountain Falls. "By then, the speaker designs I had been working on in my spare time were much better than ever before," Johnson explained. "Yet, if they were to improve beyond that point, I needed to answer some basic questions with my own research, since I had not seen any related to my questions. The experiments I needed to run required hours of solitude and an extremely quiet background, so off to the mountains I went." During the two years he lived at the lodge, Johnson created and tested speaker designs. He also analyzed other speakers on the market and studied sound, recording, and psycho-acoustics.

Recruited to create and manage a chain of high-performance stereo stores, he returned full-time to Colorado Springs in 1979. Later, he set up more disco sound systems and recorded live concerts in venues ranging from nightclubs to concert halls, across a range of music genres from bluegrass, jazz, and reggae to rock and classical.

Contracted as the recording engineer for the Colorado Springs Symphony Orchestra in 1981, Johnson was the first to record them in the city's new Pikes Peak Center for the Performing Arts, (left). Among the artists recorded during his four-year tenure were Vladimir Ashkenazy, Nadia Salerno-Sonnenberg, and Eugene Fodor. He also mixed sound for television broadcasts and radio simulcasts. "It is a gift for a recording engineer to record world-class artists in a similar facility," he reflected. "In terms of acoustic quality, the Center is still among the top 10 venues in the country." Photo taken during a concert that Johnson was recording >

Inspired to return to university

By this time, Johnson had finished studying hundreds of the scientific and engineering research papers given to him by his HP colleagues almost 10 years earlier. "It was one thing to read them and another to really study them and conduct my own experiments," he reflected. "Then I would develop mathematical equations and new research would be published that helped me better understand a previous equation."

He was astonished to see that too many of his predecessors had taken shortcuts in their mathematical equations. They had either misjudged how best to include the time-domain in their math or ignored it altogether in their quest to simplify extremely difficult equations. "For example," he said, "they had used math which described the loudness of each tone but had not cared when each tone arrived."

The designer was disappointed to see those shortcuts repeated so often that they had become accepted practice. "I knew I was on the right track," he remembered. "Although at times it felt like I was going around in circles. At that point I knew I needed to master time-domain mathematics, which is taught as part of the advanced physics curriculum. I also wanted to learn more about materials engineering."

In 1986, Johnson enrolled at the University of Colorado, Colorado Springs, to major in physics with an emphasis on solid-state physics. His coursework focused on all activity outside the nucleus, including those electron-electron and electron-nucleus interactions that define materials science. During his third year at university, the physics professors asked the designer to begin master's coursework in solid-state physics and teach undergraduate physics classes. He then studied complex time-domain mathematics and the applications of Green's Functions, along with space-time behaviors of electro-magnetic waves, down to the quantum level, including super-conductivity.

The designer held five jobs while attending school, including designing multi-kilowatt, ultra-hifi sound systems for a chain of billiards parlors. He also designed a hydro-dynamic force measuring system for the U.S. Swimming's International Center for Aquatic Research at the U.S. Olympic Training Center.

"I also developed and sold my first commercial speaker, the M-3, during that time," he said, remembering how Green Mountain Audio was established in 1988. "Although non-resonant, too much of my technology was limited by the M-3's conventional cabinet." Johnson used the new mathematics he was learning in school to re-calculate some equations in the published research he had been studying for several years and also within his own formulas.

Equipped with the M-3 experience and his new mathematical formulas, Johnson wrote a report required for graduation that became another turning point for the young designer. "Requirements for the Design of a Time-Coherent Loudspeaker with a Dispersion Pattern Decreasing Monotonically with Increasing Frequency" was the "first mathematical derivation of a monopole speaker with a dispersion pattern that smoothly narrows as the musical scale is ascended," he explained.

The result was speaker performance that blended more perfectly in the typical rooms for which studio engineers mix their sound. "I put every variable in that paper with which to design a loudspeaker that was better in every area of performance," he remembered. "The results clearly showed that I could no longer use conventional cabinetry," he said, referring to the M-3. While finishing his bachelor's degree in 1990, Johnson applied the report's results to a speaker he was developing, the Imago. "It was a no-holds-barred design," he said. The new speaker was introduced at the Consumer Electronics Show, in January 1991.

The number of orders received at the show forced him to focus on his new company instead of completing the master's degree. "I needed only two classes in quantum mechanics to graduate," he recalled. "However, I had received a lot of orders for the Imago and was developing the Diamante. It was an exciting time." He later bought the textbooks and studied quantum mechanics on his own.

It was during this heady period that, unbeknownst to him, Johnson was selected to teach physics classes at the university but because of a clerical error, was never notified. "I was busy with the Imago and Diamante," Johnson said. "A few years later I happened to see one of my professors, who told me that I had been their first choice for a new teaching position. Although I never applied for the opportunity, I was heartbroken because I enjoyed teaching and wanted to become a professor."

Breakthrough achievements

Some 30 years after building his first pair of speakers, in 1999 Johnson gained control over the generation of sound waves at all frequencies -- and today remains the only speaker designer in the world with this achievement.

Of all of his advancements across the spectrum of design details, Johnson considers his 2001 breakthrough in Zobel circuit design the "final piece of the puzzle" in his quest to conquer loudspeaker design. The result was such a dramatic improvement to the sound quality that he designed new crossovers for all the speakers sold up to that point.

Often described as a "genius speaker designer," Johnson is renowned as the world's top authority for first-order crossover circuits. His speakers typically receive standing ovations during demonstrations and have earned many accolades and awards.

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