David W. Gunness (born November 7, 1960) is an American audio engineer, electrical engineer and inventor. He is known for his work on loudspeaker design, especially high-output professional horn loudspeakers for public address, studio, theater, nightclub, concert and touring uses.
Gunness worked with Electro-Voice in Michigan for 11 years, filing three patents related to horn technology. He worked at Eastern Acoustic Works (EAW) in Massachusetts for 12 years, filing three patents in the process of creating a wide variety of loudspeaker products. For EAW, Gunness developed "Gunness Focusing"—a system for decreasing temporal response distortion in loudspeakers, involving the processing of the audio signal before it reaches the loudspeaker drivers, applying a reverse image of the expected distortion to cancel out the loudspeaker's idiosyncrasies. Gunness co-founded Fulcrum Acoustic in 2008: a loudspeaker company with the aim of designing loudspeakers based on digital signal processing (DSP), innovative components and high quality construction.
Early life Gunness was born November 7, 1960; he grew up in Janesville, Wisconsin, enjoying outdoor activities such as bicycling, camping, hunting and fishing. At Joseph A. Craig High School he participated in gymnastics and played guitar. Two of his sisters entered the University of Wisconsin–Madison (UW-Madison), but Gunness chose Purdue University in Indiana. After one year there, he returned to Wisconsin to enroll at UW-Madison as an electrical engineering major. During his college years he made extra money as a musician; singing and playing acoustic guitar. For these gigs he fabricated his own loudspeakers, and he determined to continue in this field, shifting his studies to focus on acoustics and electronics. In June 1984, Gunness graduated UW-Madison with a degree in Electrical and Computer Engineering. He immediately accepted an engineering job in Buchanan, Michigan, and relocated there. On September 29, 1984, he married Kathryn A. Sessions, a nursing student who had finished one year ahead of him at UW-Madison.
Electro-Voice
Directly after graduating UW-Madison, Gunness obtained a research and development position in the engineering department at the Electro-Voice (EV) factory in Michigan. Under Chief Engineer Ray Newman, Gunness worked on loudspeaker design, combining traditional empirical R&D methodologies with the emerging capabilities of computer analysis. His first assignment was to help develop the Musicaster 100, an all-weather 2-way coaxial loudspeaker; an update of the classic 1959 Musicaster design.
In 1984, Gunness filed a patent for a better way to use a manifold to combine the outputs of multiple compression drivers for increased sound power level (SPL), using two to four flat reflecting surfaces in the throat of a horn to redirect sound waves for a more coherent summation. "Multiple driver manifold" David W. Gunness, for Electro-Voice, Inc. Filing date: November 15, 1985. Issue date: December 16, 1986. This low-distortion manifold design made it possible for EV to produce its first high-power concert and touring loudspeaker: the MT-4, with "MT" standing for "Manifold Technology". This was a 4-way system split between two enclosures, with four speaker drivers summed in each bandpass; a total of 16 drivers. The upper two bandpasses used the Gunness manifold design for compression drivers, each manifold formed of two zinc castings. The medium low frequencies were carried by four cone drivers summed using a larger embodiment of the Gunness manifold concept based on ray tracing and reflection. Hosted by fulcrum-acoustic.com The MT-4 was a very heavy system at , but it put more power into a smaller package, and it was quicker to position and connect. The MT-4 proved popular, used on major tours and festivals such as the 1995 Monsters of Rock at Donington Park in central England and the main stage of the 1996 Lollapalooza tour featuring Metallica and Soundgarden. Together, EV engineer David Carlson and Gunness presented a paper to the Audio Engineering Society (AES) in November 1986, describing the methods they used to sum four drivers in each bandpass.
In 1986, Gunness developed the EV HP series of horn loudspeakers based on the constant directivity (CD) characteristics described by EV engineer Don Keele in the mid-1970s. Gunness recognized that relatively large 2-inch (51 mm) horn throats, commonly used for greater SPL, produced an undesirable narrowing of the output pattern above 10 kHz. His patented design used two longitudinal ribs or vanes to form three "pseudo horns" within the horn flare. "Constant Directivity Loudspeaker Horn" David W. Gunness, for Electro-Voice, Inc. Filing date: February 21, 1986. Issue date: August 11, 1987.
In 1989, Gunness developed an asymmetric horn with an output pattern shaped to suit a typical small-to-mid-sized rectangular auditorium with people sitting near the enclosure hearing sound that was not too loud and others sitting farther away hearing sound that was loud enough. In both cases, the sound pattern was to minimize sound energy bouncing off of walls; reflections creating unwanted multi-path cancellations. The horn featured a vertical diffraction slot that was narrower at the bottom which reduced the output for people sitting below the enclosure in the nearfield, and increased the output for those sitting farther away. "Loudspeaker and Horn Therefor" David W. Gunness, for Electro-Voice, Inc. Filing date: December 8, 1989. Issue date: June 4, 1991. EV's sister company, Altec Lansing, marketed this product as the "Vari-Intense" horn.
Gunness researched automated methods for analyzing the performance of a loudspeaker. In 1990 he delivered a paper to the AES describing a system which used pink noise and a filtered receiver to generate polar response curves plotting loudspeaker output patterns.
Eastern Acoustic Works In September 1995, Gunness moved his family, now including a son and a daughter, from Michigan to Massachusetts in response to his taking a position as senior engineer at Eastern Acoustic Works (EAW) in Whitinsville. His first task was to set up a system for creating custom loudspeaker designs for specific clients and purposes, and he performed much field work, tuning and optimizing loudspeaker installations. He then began to research the concept of phased point source behavior with the goal of controlling the directional characteristics of a high-powered concert loudspeaker cluster. This work led to the development of EAW's KF900 series concert touring system. In 1997 he filed two patents related to this research: one for a downfill loudspeaker that would direct sound downward without being rigged differently than its upper neighbors, "Downfill Speaker for Large Scale Reproduction System" David W. Gunness, for Eastern Acoustic Works, Inc. Filing date: August 29, 1997. Issue date: December 28, 1999. and a method for creating a "common acoustical wavefront" of horizontally arrayed loudspeaker horns mounted in trapezoid enclosures which placed the acoustic center of the array very close to the rear of the enclosure.Ballou 2012, p. 652 The horn mouths minimized diffraction between enclosures. "Large Scale Sound Reproduction System Having Cross-Cabinet Horizontal Array of Horn Elements" David W. Gunness, for Eastern Acoustic Works, Inc. Filing date: October 31, 1997. Issue date: January 18, 2000. The KF900 system incorporated digital signal processing (DSP) for each horizontal row of drivers in the loudspeaker cluster. Gunness said that bringing the DSP to fruition by way of rigorous mathematical performance analysis was a "massive undertaking" which gave him a broad foundation of computer analysis techniques he would draw from in later inventions. The KF900 was deployed in mid-1998 for 11 Promise Keepers tour dates, and its response was measured during the shows as part of an iterative product optimization plan. In 2001, Eric Clapton used the KF900 system while touring in support of his Reptile album. In his work to predict the performance of various KF900 loudspeaker configurations, Gunness used acoustical measurement and modeling software called FChart that he started developing while still at Electro-Voice. Heinz Field, home of the Pittsburgh Steelers football team received an installed KF900 system, as did Fenway Park, home of the Boston Red Sox baseball team. The final system tuning at Fenway was performed using Smaart software.
Gunness also designed the following EAW loudspeaker models: the long-throw MH433 trapezoid with rigging points, the install-only BH822 twin 12-inch "super" subwoofer, the LA400 touring subwoofer, and the large format arrayable MQ series.
Gunness Focusing For years, Gunness had been looking for various electronic solutions to the undesirable characteristics of horns. At EV in 1985, Gunness noticed the performance differences between various shapes of horns, and theorized that an electronic filter might allow optimization. In early 1995, EV gained access to Altec Lansing's 1987 Acousta-CADD acoustic modeling software which revealed more loudspeaker performance characteristics than had previously been observed, but DSP programming tools were still inadequate for audio signal correction. In 2000, Greek electroacousticians John Mourjopoulos and Panagiotis 'Panos' Hatziantoniou described a method for smoothing precise audio analysis filters. Building on this work, Gunness led a team of EAW engineers to develop a proprietary wavelet transform spectrogram for internal research. The EAW spectrogram reduced visual complexity by applying a zero-phase-shift low-pass filter to the audio signal under test using mirror-image infinite impulse response (IIR) filters. Hosted by EAW.com The spectrogram revealed loudspeaker performance anomalies, allowing the engineering team to identify mechanisms they characterized as "two-port systems"; i.e. mechanisms demonstrating a single input, a single transfer function, and a single output. Such two-port systems were of interest because they could possibly be corrected with electronic filtering. Because of their variability the methodology would not be used on any of the mechanisms which appeared to be non-linear relative to signal level, spatial distribution ("coverage"), or over time, such as cone stiffness or surround compliance. This left several substantial "linear, time-invariant" (LTI) mechanisms that would yield to correction by digital filtering. These included 1) time-smear from the compression driver/phase plug interface, 2) horn resonance, 3) cone resonance, and 4) crossover phase linearity between adjacent bandpasses. In April 2005, EAW announced the NT Series, a line of 2-way bi-amplified self-powered loudspeakers incorporating the "new technology" which was initially called "Digital Transduction Correction" (DTC). Mix magazine quoted Gunness identifying compression driver "time smear" as a longstanding loudspeaker problem that was countered by preconditioning in the audio signal. Later that year, EAW dropped the DTC acronym and began promoting the technology as "Gunness Focusing".