RIP Dr. Bruce Edgar
Another audio legend left our world as Dr. Bruce Edgar passed away January, 2021. His contributions to audio were primarily horn speaker designs and he is best known for the Titan Horn System and Seismic Subwoofer. Dr. Edgar’s education included an undergraduate degree in Electrical Engineering and a Masters in Antenna Research from Oklahoma State University. He received his Ph.D. in Electrical Engineering at Stanford University and later earned a Post Doctoral degree in Atmospheric Physics at the University of Florida. Dr. Edgar’s professional career began in 1974 with Aerospace Corporation where he was involved in six satellite experiments as well as Mission Planner for the DOD Space Test Program. He is credited with 25 scientific papers, some published in Speaker Builder Magazine.
In 1994 Dr. Edgar started Edgarhorn where he designed folded bass and Tractrix midrange horns. The latter design, rediscovered and popularized by Dr. Edgar, was of most importance to his work. The popular horns of Dr. Edgar’s day used exponential contours which is the exponential rate at which the area of the horn changes as a function of distance and frequency. As a result, the wave front drags along the horn walls. The Tractrix curve was relatively unknown and while it was patented by Paul Voigt, it was Dr. Edgar who refined the Tractrix curve into a practical low coloration audio component, designed such that its curved wave fronts ran all the way through the horn.
The Tractrix midrange horn designed by Dr. Edgar was subject to significant experimentation before results determined the optimal size of 300 Hz. The Tractrix design clearly distinguished itself from classic 40s and 50s exponential horns that produced mouth reflections and standing waves giving these horns a megaphone like coloration. In comparison, Dr. Edgar’s Tractrix flare sounds quite natural and has been accepted by several manufacturers as the most appropriate choice for high-end music reproduction.
Later in his career, Dr. Edgar was a speaker design consultant. Projects using field coli drivers caught his attention and most recently he was assisting in the design of ESD Acoustics horn speakers. He was also very generous with his advice and some of his designs made their way into the DIY community. It was not unusual to see Dr. Edgar at audio shows although as his health declined so did his attendance. However, at the peak of his career Dr. Edgar’s speakers could be heard in multiple rooms at the Las Vegas audio shows, with some being integral to rooms that won best of show.