page_title: Dan Dugan (audio engineer)
section_title: Automixer
hierarchical_section_title: Dan Dugan (audio engineer) / Automixer
caption_attribution_description: English: Dan Dugan standing near 37 years of his automixers. In his right hand, Dugan holds his Yamaha Dugan-MY16 card (2011) and to his left side are many of the previous models he produced or licensed. On top of the rear rack is the light blue prototype of the Model D from the late 1980s. Descending in the rack: the Altec 1684A, the Altec 1678C, 1678B, 1678A, two white faceplate Dugan Model As (8- and 6-channel units), and with red labels on bare steel, the 1974 prototype of the Dugan Music System. Under Dugan's left hand is a Dugan Model E-1 (2008), below that a controller for the Dugan Models D-2 and D-3, and at the bottom is a Model D.
context_page_description: Dan Dugan is an American audio engineer, inventor, and nature sounds recordist. He was the first person in regional theatre to be called a sound designer, and he developed the first effective automatic microphone mixer: the automixer. Dugan's sound design work was acknowledged in 2003 with a Distinguished Career Award by the United States Institute for Theatre Technology.
  In his youth, Dugan was fascinated by the technical aspects of theatre. He worked as a lighting designer then transitioned to sound design in 1967. Dugan became interested in achieving the automatic adjustment of sound controls after a frustrating experience staging the musical Hair. His first automixer design was not fully practical but his second design was successful; it used a reference derived from a total of all of its microphone signals. Dugan devised a third improvement which helped prevent audio feedback in the presence of sound reinforcement loudspeakers. Dugan next produced an automixer design that could be inserted into an existing mixing console. This proved popular for broadcast and live sound applications. Each of Dugan's subsequent automixer models has been of the insertable type.
context_section_description: While designing sound for the musical Hair, Dugan began to appreciate the human operator's inability to act quickly enough to control multiple microphones. He saw the show's audio mixing person "working rotary knobs for 16 area mics, 9 hand mics, and 10 mics in the band". Dugan thought that a microphone should not be turned on unless it was getting some worthwhile signal, more than just the room ambiance. His frustration with microphone mixing led him to experiment for a few years with microphone signals controlled automatically by voltage-controlled amplifiers (VCAs), finally developing the "Dugan Music System", shown to the AES at their 49th convention, held in New York in 1974. This system used a novel proportional gain algorithm whereby the total gain was divided between all active microphones. The microphones were "continuously and automatically adjusted" by a set of VCAs to bring each microphone up or down in the mix, based on how much signal it was sending relative to the signal received by a reference microphone placed somewhat distant from the other microphones. Dugan's patent application for a "Control Apparatus for Sound Reinforcement Systems" was accepted and published on June 4, 1974. This was the first useful automatic microphone mixing algorithm, the basis for all of Dugan's later systems.
  
  Though the algorithm was good, the reference microphone was an unpredictable variable: it had practical placement problems. If it was near the audience, audience noise would skew the algorithm. If placed backstage, crew and equipment noises could be a factor. Thus, the Dugan Music System was not immediately developed into a product. Dugan studied the problem, researching alternative solutions. In 1975, Dugan filed a patent for the "Dugan Speech System", and in 1976 produced 60 copies of what he named the Dugan Model A. The automixer with serial number 1, a unit Dugan fabricated by hand, "was installed in the conference room of Bell Labs by Harvey Fletcher". Significantly, the external microphone reference of the Dugan Music System was replaced by a reference composed of the total signal received from all of the active microphones. Dugan described the process some three decades later: 
  "I was messing around with logarithmic level detection, seeing what would happen if I used the sum of all the inputs as a reference. That's when I accidentally came upon the system. It was really discovered, not invented. I didn't really know what I had, just that it worked like gangbusters."
  Dugan licensed this more practical system to Altec who produced 4- and 8-channel automixers for commercial installations such as hotels, conference rooms, courtrooms and city council chambers. The Dugan Speech System was the first commercially successful automixing algorithm. Over the next 15 years, other manufacturers designed competing automixers, and the market segment was born.
  In the late 1980s, Dugan developed a gain limiting improvement to the automixing algorithm. The Dugan Gain Limiting System was patented in September 1989 and presented to the 87th AES convention in October. Dugan described for the AES his prototype of an automixer to be inserted into selected microphone channels of a mixing console, operated by a person, to help in mixing multiple live microphones to have less reverberation and noise, more focus on the desired sound, eliminating the mixing engineer's problem of too-slow human reaction time. The gain limiting system provided smooth, continuous control over the equivalent number of open microphones (NOM) that the automixer would send at its outputs. The NOM could be set anywhere between 1 and 10, with higher settings sounding more natural for a recording in a studio, and lower settings offering greater control of acoustic feedback in the presence of sound reinforcement loudspeakers. An embodiment of Dugan's three patents was produced as the Model D Automatic Mixing Controller, a 3U rack unit handling 8 channels which could be linked with up to 11 other Model Ds to automatically mix as many as 96 channels simultaneously.
  Dugan
caption: Dugan holds his Yamaha Dugan-MY16 card (2011), and to his left are earlier automixer models
exif: {}