This book is a study of the workings of dynamic loudspeakers and dynamically forced vibration. With its wealth of practical observations and real-life examples, this work will prove invaluable to the practicing motor design or loudspeaker design engineer, as well as researchers and students in electroacoustics.
The book is based on a lifetime’s accumulated knowledge by acclaimed speaker designer William H. (Bill) Watkins. It differs from the usual tone of most technical books on this subject by initially presenting, and analyzing in full, the function of each key parameter of a reference dynamic loudspeaker. Each parameter’s value is then calculated and also confirmed via lab measurements to vividly illustrate all energy-transduction facets of loudspeaker operation and the forced vibration. This presentation style makes the analysis both more engaging, intuitive, and easier to comprehend compared to most previous works in the field. The principles of this book apply to all direct reciprocating motors, not just those in a dynamic loudspeaker. Unique to the book is an entire chapter dedicated to the discussion of back-EMF voltage, discussed from several technical points of view and analyzed in depth as related to the dynamic transfer of energy between the mechanical and electrical domains. Another unique feature is a detailed discussion of Watkins’ patented dual-motor concept to achieve high dynamic speaker performance in the region of its low-frequency resonance.
Author(s): William H. Watkins
Publisher: Springer
Year: 2022
Language: English
Pages: 136
City: Cham
Preface
Acknowledgment
About the Author
Introduction to Loudspeaker Physics and Forced Vibration
Contents
Chapter 1: Prologue
1.1 Abstract
1.2 Elaboration
Chapter 2: Preliminaries
2.1 General Measurement Conditions and Procedures
2.2 Assumptions and Limitations
2.3 Electrical, Mechanical, and Acoustic Analogies
2.4 Power-to-Loss Ratio and Volume Acceleration
2.5 Terminology
Chapter 3: Analogous Electrical Circuit
3.1 Analogous Circuit and Discussion
3.2 Reference Driver Magnitudes in the Analogous Circuit
Chapter 4: Electrical Impedance
4.1 Coil Resistance
4.2 Resistance Due to the mechanical and Acoustic Load
4.3 Core Resistance
4.4 Blocked-Coil Measurement
4.5 Source and Total Resistance
4.6 Reactance
4.7 Inductance
4.8 Impedance Expressions
4.9 Voltage and Power Expressions
Chapter 5: Efficiency and the Mechanical Response Function
5.1 Efficiency at the Working Frequency
5.2 The Mechanical Response Function
5.3 Relation of Above Parameters and Power
5.4 Correlation with Kinsler, Kloss, and Small
5.5 Efficiency Expressions and Loss
Chapter 6: Back EMF
6.1 Faraday´s and Lenz´s Laws
6.2 Transfer of Energy
6.3 Degree of Current Flow
6.4 Newton´s Laws
6.5 Conservation of Energy
6.6 Back emf and Power Transfer
Chapter 7: Mechanical and Acoustic Load Impedances
7.1 Mechanical Plus Acoustic Impedance
7.2 Equivalent Mechanical Resistance
7.3 Air Load Resistance
7.4 Mechanical Resistance
Chapter 8: Mechanical and Acoustic Power
8.1 Electrical Power Factor
8.2 Mechanical Power Factor
8.3 Mechanical Plus Acoustic Power
8.4 Relations of Acoustic Power
8.5 Energy and Power Distribution
Chapter 9: Low-Frequency Response
9.1 Half-Power Point
9.2 Maximum Amplitude
Chapter 10: Force
10.1 The Lorentz Force Law
10.2 Motor Resistance and Electromagnetic Damping
10.3 Correlation with Beranek´s Velocity Expression
10.4 Relation to the Power-to-Loss Ratio
10.5 Force Expressions
Chapter 11: Velocity
11.1 Average and RMS Velocity
11.2 Velocity Relationships and Expressions
11.3 Measured Velocity
11.4 Recoil Velocity
11.5 Volume Velocity
Chapter 12: Energy
12.1 General Considerations
12.2 Kinetic Energy
12.3 Relation of Kinetic Energy to Source Power
Chapter 13: Work, Efficiency, and Power
13.1 Work Done Heating the Coil and Core
13.2 Work Done on the Mechanical and Acoustic Side
13.3 Relation to Power and the Power-to-Loss Ratio
Chapter 14: Resonance, Q, and Measurements
14.1 Mass, Compliance, and Mechanical Resonance
14.2 Bandwidth
14.3 Quality Factors at Resonance
Chapter 15: Related Parameters and Measurements
15.1 Acceleration
15.2 Amplitude
15.3 SPL
15.4 Motor Strength
15.5 Measuring Bl with Precision
15.6 Momentum
15.7 Pressure
Chapter 16: Circumventing Efficiency and Bass Extension Limitations
16.1 Efficiency and Bass Extension Limitations
16.2 Back EMF
16.3 Dominant Parameters
16.4 The Conventional Trade-Off
16.5 Dual Motors
16.6 Technical Details
16.7 Summary of This Chapter
Appendix A: Parameter Magnitudes and Parameter Tables
Parameter Magnitudes
Parameter Tables
Appendix B: New Loudspeaker with Extended Bass
Back EMF
Dominant Parameters
The See-Saw Effect
Dual Motors
Performance
System Performance
Glossary and Symbols
References
Index
