The history of pro audio is a short 125 years — barely a ripple in geologic time. But a lot has happened in that century and a quarter.

Three years ago, the Mix Foundation created the TECnology Hall of Fame to spotlight pro audio's history. Selecting a few inductees each year from a 125-year heritage is not easy: An elite committee of more than 50 industry leaders, engineers, producers, designers, educators, journalists and historians volunteered to help.

Once the results were in, I wrote narratives putting each into a historical context. Many manufacturers are long since out of business. At some companies, no one remains with any knowledge of the product. Unfortunately, the history of pro audio — our very lineage — is woefully neglected. Sources are scarce, sometimes impossible to find.

Information about the 40 previous inductees can be found at www.mixfoundation.org. But meanwhile, set your time machine (analog, of course) back and enjoy this ride through the annals of audio.

Edward Christopher “EC” Wente had a fruitful career during his tenure at Western Electric/Bell Labs from 1914 to 1954. Working to improve telephone audio, in 1916 he patented a “telephone transmitter” — better known now as the condenser microphone. This first design was fairly crude, but provided remarkably flat performance compared to the carbon mics used at the time. His design featured a 1.9-inch diameter and 22-micron diaphragm with a 15kHz bandwidth — astonishing in the days when 78 rpm acoustic recordings topped out around 3 kHz.

Over the years, Wente's condenser designs fueled the impending revolutions in the electrical recording process and motion picture sound. Western Electric's condenser lineup expanded with models such as the 7A/8A/9A/10A/47A/53A offering tabletop, floor stand and hanging variations.

Wente's other innovations were many, including the compression driver, the dynamic mic, the multicell horn, a “light valve” for translating audio into variable-density patterns for film soundtracks, and contributions in auditory perspective, anechoic room design and acoustical wall materials.

Nearly 75 years ago, Harvey C. Fletcher and Wilden A. Munson — two Bell Labs engineers studying subjective loudness — changed our understanding of the hearing process. Asking a large number of subjects to compare the relative volume of two tones to a standard 1kHz tone at a set level, Fletcher and Munson defined human hearing awareness at various frequencies.

In the October 1933 edition of the Journal of the Acoustical Society of America, Fletcher and Munson showed that hearing is frequency-selective — more specifically, hearing is most sensitive to pure tones in the 3 to 4kHz range and less so above and below that. To perceive that a 100Hz signal is of equal loudness to a 3kHz tone requires an actual SPL of the 100Hz tone that's much higher than that of the 3kHz tone, particularly at low volumes. This phenomenon was referred to as “Equal-Loudness Contours,” and although this original research was later updated (most notably by Robinson and Dadson in 1956), Fletcher and Munson's pioneering work laid the groundwork for industry-standard measurement curves, from the classic A/B/C/D-weighting filters to the current ISO 226:1987 standard.

In the late 1920s, cinema audio playback was dismal. Western Electric had a single driver on a large re-entrant horn. It didn't sound very good, even after the company added a separate HF unit and extra 18-inch woofers. RCA's competing system was no better.

Dissatisfied with these bulky, 5kHz bandwidth systems, MGM's sound department head, Douglas Shearer, set out to create something better. Shearer asked John Hilliard to head the team, with Robert Stephens and Harry Kimball. Consultant John Blackburn suggested using James B. Lansing's new high-performance components. Essentially, Shearer created a dream team with some of the best minds in audio. Other ideas came from William Snow, who worked with Harvey Fletcher at Bell Labs, and RCA's John Volkmann and Harry Olson.

Known as the Shearer Horn, the two-way system had a large multicell horn coupled to Lansing's new 284 compression drivers. One or more “W” bin folded horns loaded with two 15-inch Lansing woofers handled LF. On its debut, the Shearer Horn was a near-instant success, offering high-SPL/high-fidelity performance from a package that could be easily shipped and installed. Thousands of Shearer-style systems (from a variety of suppliers) were in theaters everywhere, and the system received a technical Academy Award in 1936.

The Shearer Horn began the age of modern sound systems. Equally significant was its role in launching an entire industry of pro audio with an awareness for fidelity. The system's lifespan was cut short by Altec A-4 Voice of the Theatre models in the mid-1940s (designed by Hilliard and Lansing), but innovations such as the “W” bin design stayed in use for another half-century.

When clock manufacturer Laurens Hammond introduced his first tone wheel organ in 1935, he had no idea that he'd launched a groundbreaking instrument that, more than 70 years later, would still have a major effect on musical styles. Initially, the Hammond organ was intended for churches and homes, but the semi-portable (only 400-pound!) model B-3 in 1954 brought this instrument to the forefront of jazz, R&B and rock 'n' roll. The B-3 was the right instrument at the right time, but its soulful versatility and great voicings (combined with a Leslie rotating speaker from Don Leslie) soon made the instrument a mainstay in every genre of pop music.

With two five-octave keyboards; nine drawbars on each manual; two pedal drawbars; 10 presets; and switches for percussion, volume, decay, and harmonics and chorus/vibrato scanner, the B-3 is almost synthesizer-like, providing an incredible variety of sonic textures.

The tone wheel design uses a series of notched rotating wheels that create a tone picked up by magnetic coils, where each wheel's rotational speed and number of notches determines its pitch. Minor variations at each point in the tone wheel help create the organic Hammond sound that simply can't be duplicated by samplers and synthesizers.

The development of Sel-Sync^™ (Selective Synchronous) recording by Ampex a half-century ago eventually turned the recording world upside down, yet it was a quiet step with little fanfare. The impetus for multitracking came from Les Paul, who was doing sound-on-sound recording as early as 1949 on a tape deck modified with an extra head and a switch to defeat the erase function. However, the technique was risky: One bad pass and the recording was ruined, and each additional pass added noise and distortion.

With the concept for an 8-track in mind, Paul met with Ampex, which started the project in 1953. The task required designing new record/play and erase heads, and the difficult switching of very low-level/high-impedance circuitry to achieve exact sync for monitoring previous tracks while overdubbing new ones. Ampex engineer Mort Fujii felt it could be done, and the first 1-inch Sel-Sync 8-track (based on an instrumentation deck) went to Paul two years later for $10,000 — a sum that could have bought two nice houses at the time.

Ironically, Ampex's attorney advised the company that the concept was “obvious engineering” and non-patentable, so no patent for multitracking was ever issued.

There are many fans of Telefunken mics, with its U47 and ELA M Series leading the pack. However, Telefunken never built mics, instead outsourcing manufacturing to Neumann and AKG, which made models that bore the Telefunken name.

In the late '50s, Neumann established its own U.S. distribution and stopped supplying U47s to Telefunken. Seeking a high-quality studio replacement, Telefunken asked AKG to create a multipattern tube condenser that had its pattern control switching on the mic body and the result was the ELA M 251 and ELA M 250. The latter was an omni/cardioid design, while the three-pattern 251 added a figure-8 pickup. All used the proven CK12 capsule employed in AKG's famed C-12.

Nearly a half-century after its introduction, hundreds of vintage Telefunken ELA M 251/250s are in use worldwide and still prized by engineers for their smooth vocal reproduction and sparkling high-end response. But credit should be given to AKG for designing this timeless, enduring classic.

When a microphone remains in production for nearly 40 years, words like “studio standard” certainly apply, but the roots of the U87 go back much further. In 1960, Neumann launched the U67, a three-pattern tube mic for close-miking that was intended as a replacement for the U47. Designed by Neumann's Dr. Gerhart Boré, the U67's great sound and modern, tapered, shaft body made it an instant success. In 1966, Boré's team was asked to create a solid-state version of the U67. The transistorized U87 was unveiled in 1967.

The U87 used the same K67 capsule as the U67 and did not require an external power supply. This was a major convenience, although the original U87 had a internal battery compartment housing two 22.5-volt batteries to augment the phantom power to the capsule's 60V requirement. Later, a DC/DC converter was installed in place of the difficult-to-find 22.5V cells, and the new model U87A could run solely on phantom power. Replacing the Tuchel output connector with a standard XLR jack, the mic was designated U87 Ai. The model is still in production, with thousands in use throughout the world.

In 1967, Richard C. Heyser, a research engineer at the Jet Propulsion Laboratory of the California Institute of Technology published a paper in the AES Journal titled “Acoustical Measurements by Time Delay Spectrometry.” It described a technique whereby loudspeakers and other electro-acoustical systems could be measured in real-world spaces — without an anechoic chamber. Unfortunately, the horsepower to perform such computations using 1960s technology was impossible, but Heyser's TDS concept drew wide acceptance.

Later, educator Don Davis organized a seminar for 20 leading audio researchers, with California Institute of Technology offering them licenses to build and operate TDS devices created by combining off-the-shelf products with a custom Heyser-designed interface.

TDS went big time in 1983, when Crown's Techron division unveiled the TEF System 10, the first portable TDS analyzer/acoustical measurement system. Encompassing the gamut of TDS measurements, TEF (Time-Energy-Frequency) included energy time curves and the ability to show waterfall displays of audio spectra. The 40-pound suitcase unit included 96 kilobytes of RAM and a 9-inch green-phosphor screen, and it cost $14,500. However, acoustical research would never be the same, as for the first time, complex on-site measurements of systems and spaces were possible from a commercially available unit.

Speaker design has long been considered some kind of black magic. Yet a major step forward came when two researchers, following earlier work by Leo Beranek, published their findings regarding the relationship of loudspeaker parameters to low-frequency performance in vented cabinet enclosures and simple methods of measuring them. Among these were the driver's free-air resonance, electrical and mechanical Q, DC resistance, efficiency, piston area, thermal power rating, etc.

In 1961, an Australian broadcast engineer named Neville Thiele published a paper in a radio/electronics journal describing his work in simulating loudspeaker response as electrical filters as a means for speaker design. Several years later, Richard Small, an American studying in Sydney read the paper and convinced the University of Sydney to let him enroll for a Ph.D., expanding and refining its premise. With the help of colleague Robert Ashley, Small convinced the AES to reprint Thiele's original paper in 1971 and followed it up with a series of his own papers. The effect of the Thiele-Small research was dramatic, not only influencing manufacturers to provide more details about the drivers they built, but also bringing about a new era in the predictability of loudspeaker response based on enclosure volume and port dimensions.

In the mid-'70s, UREI founder Bill Putnam — unhappy with the sound of the Altec 604 monitors in his United Western Studios — worked with UREI's Dean Austin and Dennis Fink on ways to improve the 604. They replaced Altec's multicell horn with a wider dispersion design and added a 15-inch Eminence woofer to boost LF output. Ed Long applied his Time-Align^™ crossover techniques to achieve time- coherent, true point-source performance.

Engineers and producers mixing on the system were so enthusiastic about its sound that UREI started producing the monitors as a commercial product, with the first UREI 813 debuting in 1977. Typically soffit-mounted, these large, double-15 monitors were ideal for the larger, higher-SPL control rooms of the time.

Two years later, Altec replaced its Alnico 604-8H with a ferrite model, requiring modifications to the 813 design, including a foam diffraction buffer, crossover mods and small Helmholtz resonators in the horn flare. This 1979 model was the 813A, followed by the 815A (a 604, plus two extra woofers) and the single-driver 811A, but the 813A was far more popular.

Financial and QC problems at Altec led UREI to find a new driver source, now mating PAS coaxial 15 to a JBL 2425 compression driver. The new 813B version debuted in 1983. Later that year, Putnam sold the business to Harman, with UREI becoming a division of JBL Professional; the 813C, a new model with all JBL drivers, launched in 1984. But in its various incarnations, the UREI 813 was the most successful large-format studio monitor ever made.

Unveiled at the AES show in 1978, the Lexicon 224 was not the first digital reverb (that honor goes to EMT's 250), but the 224 (and its 224X and 224XL cousins) was the most ubiquitous and popular high-end studio reverb in history.

The reverb was conceived when Dr. David Griesinger, a nuclear physicist/musician/classical recording engineer, started working on a digital solution to reverb. Seeing EMT's 250 encouraged him to merge a microcomputer with his reverb design. He pitched his rough prototype to Lexicon, which bought the invention and brought Griesinger on board to help refine the product. One of Griesinger's concepts for the new reverb was creating a separate control unit for parameter adjustment and program access, and the Lexicon 224 was unveiled at the AES show in 1978.

The 224 reverberation system had a console-top controller with a four-rackspace brain, two inputs, four outputs and interchangeable programs to simulate chambers, plates and rooms. The 224 was “affordable” — meaning $7,500 with two programs or $7,900 with four programs. But at half the price of EMT's 250, the 224 was a hit. Eventually, the 224 evolved into the improved 224X and 224XL, which included the LARC (Lexicon Alphanumeric Remote Control), offering fingertip access to programs and parameters, dedicated function keys and a 24-character LED.

The music industry forever changed at the 1979 New York AES Show with the introduction of the TEAC Model 144 Portastudio^®, an integrated 4-track cassette recorder with Dolby B noise reduction, 3.75 ips operation and a 4×2 mixer with pan, treble and bass on each input.

The most famous Portastudio recording was Bruce Springsteen's 1982 Nebraska album. Originally cut on a 144 with a couple of Shure SM57s, it was intended to be a demo. However, The Boss liked the feel of the songs so much that rather than recut them, he used them as the master tracks.

For musicians seeking a sketchpad for recording demos, the 144 was a runaway success with a legacy of thousands of artists and engineers today who made their first multitrack recordings on Portastudios.

In the late '70s, Sony launched a program to provide pro users with tools to support the impending consumer digital audio revolution. Toshitada Doi led a team of 30 researchers set on bringing digital to the pro market.

At the European AES Show in 1978, Sony showed a prototype 1-inch, 24-track digital recorder. It never went into production, but it laid the groundwork for Sony's popular line of half-inch DASH (Digital Audio Stationary Head) format multitracks.

In 1981, as Mitsubishi began delivering its X-800 digital 32-tracks, Sony countered with its PCM-3324 digital 24-track, which was two years from shipping. The original 44.1/48kHz, 16-bit PCM-3324 weighed 440 pounds, but had a maximum record time of 65 minutes and could easily be synched for 48-track work. Even with its $150,000 price tag, the PCM-3324 found early adopters such as Stevie Wonder, Frank Zappa and remote trucks, and a new industry emerged offering digital rentals.

The DASH spec included other variations such as 2/4/8/16-track decks, yet it was the 24-track machine that gained popularity, especially with each new generation sounding better and costing less. But the real attraction was DASH's thin-film head technology, which supported double-density tracking so tapes made on a 3324 could be played on the PCM-3348 48-tracks that followed.

Every decade or so, a keyboard instrument comes out that not only is adopted by musicians, but also shapes the course of pop music. Debuting just months after the announcement of the MIDI spec and offering a new and varied palette of tonal textures, Yamaha's DX7 was the right synth at the right time.

The magic behind the DX7's FM synthesis engine was discovered in the early 1970s by Dr. John Chowning at Stanford University. In the mid-'70s, Yamaha licensed the technology and spent nearly a decade working on the project, both in Japan and with Chowning in California.

When the DX7 launched in 1983, users were amazed by its purity of tone and its ability to mimic certain instruments — particularly struck percussion, chimes, electric pianos, etc. — and its wealth of cool synthesizer sounds. During the instrument's short tenure, Yamaha sold a then-unheard-of 200,000 DX7s. The DX7 also marked the beginnings of custom VLSI integration into musical instruments, making it affordable.

In 1984, Lucasfilm and Convergence Corp. formed The Droid Works, and under the leadership of Andy Moorer, showed its SoundDroid^™ workstation at NAB in 1985. The product was years ahead of its time and too expensive for the typical studio. In 1986, former Droid Works execs Bob Doris, Jeffrey Borish and Mary Sauer left to found Sonic Solutions.

Some months later, Andy Moorer joined the Sonic team and the company debuted NoNoise^®, a Macintosh-based system that applies proprietary DSP algorithms that eliminate broadband background noise, as well as AC hum, HVAC buzz, camera whine and other ambient noises. NoNoise could also reduce overload distortion, acoustical click/pops, transients caused by bad splices and channel breakup from wireless mics — without affecting the original source material. Sonic Solutions eventually expanded into 2-channel and multichannel workstation development and developed the first DVD premastering system.