Loudspeaker Physics and Forced Vibration

William H. (Bill) Watkins was a true American audio innovator. Developer of the famous Watkins “Dual-Drive Woofer”, the renowned WE-1 large floor-standing speaker system, the recently introduced compact Generation 4 unit, and numerous other high-performance speakers, he passed away at his home February 1, 2018 in Kingsport, TN. He was a veteran of the U.S. Army in the Korean War era and served in active duty overseas. In his youth he became an accomplished musician, especially on the mandolin, guitar, and violin. He was also a long-time member of the Audio Engineering Society, which he originally joined in 1974. He maintained an extensive library of AES publications over a span of several decades, which he heavily utilized in his ongoing audio and electroacoustics research and development activities. He had been involved in the high-fidelity audio business in Kingsport since the late 1950s, having owned and operated Watkins Stereo, a retail and custom audio firm, and Watkins Engineering, which manufactured several of his later advanced loudspeaker systems, including the highly regarded WE-1 and Generation 4 models. He was granted three U.S. patents in the area of acoustics, including U.S. #3,838,216 in 1974 for the Dual-Drive Woofer concept, which significantly improved low-end performance of an acoustic-suspension system by effectively cancelling the low-frequency resonance impedance peak, thus extending the bass frequency response by close to an octave. He also authored a landmark article on the technology, "New Loudspeaker with Extended Bass," in the December 1974 edition of Audio magazine. The patented concept was subsequently licensed to Infinity Systems in California for use in many of their high-end speaker systems and soon became widely known as the "Infinity/Watkins" Woofer. In 1982 Watkins collaborated with his son Bill Jr. on a second patent, U.S. #4,443,744, on reviewer-acclaimed sound-damping panels for home listening use, later marketed as the Watkins Echo Muffs. A third patent, on resistively damped crossover networks to optimize speaker transient response, U.S. #4,475,233, was issued to Watkins in 1984. His prolific speaker design career continued into the 21st century, culminating in the current highly reviewed compact Generation 4, a two-way system incorporating multiple patent-pending features to assure unusually wide, smooth frequency response, along with precise damping and stereo imaging from a small (½ ft3) enclosure.

Chapter 1. Glossary and Prologue.- Chapter 2. Preliminaries.- Chapter 3. Analogous Electrical circuit.- Chapter 4. Electrical impedance.- Chapter 5. Efficiency and the mechanical response function.- Chapter 6. Back emf.- Chapter 7. Mechanical and acoustic load impedance.- Chapter 8. Mechanical and acoustic power.- Chapter 9. Low frequency response.- Chapter 10. Force.- Chapter 11. Velocity.- Chapter 12. Energy.- Chapter 13. Work, efficiency, and power.- Chapter 14. Resonance, Q, and measurements.- Chapter 15. Related parameters and measurements.- Chapter 16. Circumventing Efficiency and Bass Extension Limitations.- Chapter 17. New Loudspeaker with Extended Bass.