Charlie Hughes (audio engineer)

At Peavey, Hughes served as a loudspeaker designer and the main horn designer for loudspeaker enclosures. He developed a new horn design as a means to improve linearity in mid- and high-frequency reproduction. The design was primarily a simple conic section except that its throat was curved in a circular radius arc to match the desired throat size for proper mating to the compression driver. The mathematical formula describing the cross-sectional area expansion was a quadratic equation:[3]

${\displaystyle S=Ax^{2}+B{\sqrt {r^{2}+x^{2}}}\ +C}$

This quadratic equation suggested to Hughes the name of the horn design: the Quadratic-Throat Waveguide (QT waveguide). Instead of increasing the horn mouth size with a flare to control midrange beaming, a relatively thin layer of foam covering the mouth edge was found to suit the same end. The QT waveguide, when compared to popular constant directivity (CD) horns, produced about 3–4 dB lower levels of second harmonic distortion across all frequencies, and an average of 9 dB lower levels of the more annoying third harmonic distortion. Being without a diffraction slot, the QT waveguide was free from problems with apparent apex, making it arrayable as needed for public address purposes.[3] In New York City, Hughes presented a paper on the technology at the Audio Engineering Society convention in September 1999.[4] His patent for the QT waveguide was provisionally filed on March 5, 1999, and granted on May 9, 2000.[5]

At Peavey, Hughes measured the results of his horn experiments, and he analyzed the total performance of multiple-driver loudspeakers, especially with regard to tuning the crossover to obtain optimum results. In this measurement he used TEF, a professional acoustical measurements and instrumentation system first made by Techron, a division of Crown International, then sold to Gold Line. TEF is a system that incorporates Richard C. Heyser's time delay spectrometry (TDS) method to analyze sound waves. In 1998, Hughes was appointed to the advisory committee of Gold Line's TEF division.[6] As of 2008 he was still on the advisory committee.[7] Hughes also programmed in MATLAB, a computing environment that allowed him to visualize the complex output pattern of a loudspeaker system under test. He used MATLAB to optimize crossovers to achieve smoother directivity results at the crossover transition region. Toward this end, Hughes developed a software tool called PolarSum which eliminated much of the drudge work of taking a great many polar plot measurements.[2][8] Hughes also used Enhanced Acoustic Simulator for Engineers (EASE), a 3D simulation tool which was developed by Wolfgang Ahnert and Stefan Feistel of Germany.

Hughes involved himself early with the more practical aspects of operating sound systems. He served as head sound engineer and sound designer at the Meridian Little Theatre from 1989. Beginning in 1991, Hughes teamed with Peavey Product Manager Mick Donner to form Meridian SoundWorks, a local sound reinforcement company providing gear and engineering to mix concerts, corporate and political events, and theatrical productions. Meridian SoundWorks also provided sound system design and optimization for permanent installations. The experience allowed Hughes to assess the performance of sound gear in real-world applications.[1]

In 2000, Hughes became an instructor of TEF II systems, part of a team that included Don Eger and Russ Berger.[1][2]

Hughes joined Altec Lansing in May 2002 to serve as senior engineering manager in the professional audio division. This included both component-level and overall product engineering for the installation market as well as for touring systems.[9] While at Altec, Hughes was granted two patents. The first was a patent for the optimum spacing of driver elements in a line array, using a minimum of drivers.[10] This technology, marketed as "InConcert", was at the core of Altec's compact computer speaker system FX 6021, a satellite and subwoofer system which used the patented process for its two satellite speakers, each containing six drivers mounted vertically. The two center drivers covered the frequency range from 150 hertz up to 20 kHz, the next two drivers above and below covered up to 6 kHz, and the top and bottom drivers covered up to 1 kHz. This allowed for good sounding results with six drivers mounted on a columnar surface that could physically accommodate eight or nine.[11] Hughes' third patent, his second with Altec, was a patent for a dipole and monopole surround sound speaker system which used indirectly aimed drivers added to the top of the usual front left and front right loudspeakers.[12] Altec brought the technology to market as the GT 5051R—a 3.1 system which included a center speaker and a subwoofer. The front left and right speakers bounced surround information off of the walls and ceiling for customers who did not want to clutter their listening space with a pair of rear speakers.[13]

Hughes left Altec in late 2004 to co-found Excelsior Audio in North Carolina.[2] He serves as managing director.

Biamp, an audio electronics and media networking manufacturer in Beaverton, Oregon, hired Hughes in May 2021 as principal engineer of the electroacoustics division. Biamp had recently bought Community Professional Loudspeakers of Pennsylvania, and Apart Audio of Belgium, to broaden the Biamp loudspeaker portfolio.[14]