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The Design of Active Crossovers

Book Description

The Design of Active Crossovers is a unique guide to the design of high-quality circuitry for splitting audio frequencies into separate bands and directing them to different loudspeaker drive units specifically designed for handling their own range of frequencies. Traditionally this has been done by using passive crossover units built into the loudspeaker boxes; this is the simplest solution, but it is also a bundle of compromises. The high cost of passive crossover components, and the power losses in them, means that passive crossovers have to use relatively few parts. This limits how well the crossover can do its basic job.

Active crossovers, sometimes called electronic crossovers, tackle the problem in a much more sophisticated manner. The division of the audio into bands is performed at low signal levels, before the power amplifiers, where it can be done with much greater precision. Very sophisticated filtering and response-shaping networks can be built at comparatively low cost. Time-delay networks that compensate for phyical misalignments in speaker construction can be implemented easily; the equivalent in a passive crossover is impractical because of the large cost and the heavy signal losses. Active crossover technology is also directly applicable to other band-splitting signal-processing devices such as multi-band compressors.

The use of active crossovers is increasing. They are used by almost every sound reinforcement system, by almost every recording studio monitoring set-up, and to a small but growing extent in domestic hifi. There is a growing acceptance in the hifi industry that multi-amplification using active crossovers is the obvious next step (and possibly the last big one) to getting the best possible sound. There is also a large usage of active crossovers in car audio, with the emphasis on routing the bass to enormous low-frequency loudspeakers.

One of the very few drawbacks to using the active crossover approach is that it requires more power amplifiers; these have often been built into the loudspeaker, along with the crossover, and this deprives the customer of the chance to choose their own amplifier, leading to resistance to the whole active crossover philosophy. A comprehensive proposal for solving this problem is an important part of this book.

The design of active crossovers is closely linked with that of the loudspeakers they drive. A chapter gives a concise but complete account of all the loudspeaker design issues that affect the associated active crossover.

This book is packed full of valuable information, with virtually every page revealing nuggets of specialized knowledge never before published. Essential points of theory bearing on practical performance are lucidly and thoroughly explained, with the mathematics kept to an essential minimum. Douglas' background in design for manufacture ensures he keeps a wary eye on the cost of things.

Features:

  • Crossover basics and requirements
  • The many different crossover types and how they work
  • Design almost any kind of active filter with minimal mathematics
  • Make crossover filters with very low noise and distortion
  • Make high-performance time-delay filters that give a constant delay over a wide range of frequency
  • Make a wide variety of audio equaliser stages: shelving, peaking and notch characteristics
  • All about active crossover system design for optimal noise and dynamic range
  • There is a large amount of new material that has never been published before. A few examples: using capacitance multipliers in biquad equalisers, opamp output biasing to reduce distortion, the design of NTMTM notch crossovers, the design of special filters for filler-driver crossovers, the use of mixed capacitors to reduce filter distortion, differentially elevated internal levels to reduce noise, and so on.

Douglas wears his learning lightly, and this book features the engaging prose style familiar from his other books The Audio Power Amplifier Design Handbook, Self on Audio, and the recent Small Signal Audio Design.

Table of Contents

  1. Cover
  2. Halftitle
  3. Title
  4. Copyright
  5. Dedication
  6. Contents
  7. Preface
  8. Acknowledgments
  9. Chapter 1: Crossover Basics
    1. 1.1 What a Crossover Does
    2. 1.2 Why a Crossover Is Necessary
    3. 1.3 Beaming and Lobing
    4. 1.4 Active Crossover Applications
    5. 1.5 Bi-Amping and Bi-Wiring
    6. 1.6 Loudspeaker Cables
    7. 1.7 The Advantages and Disadvantages of Active Crossovers
      1. 1.7.1 The Advantages of Active Crossovers
      2. 1.7.2 The Disadvantages of Active Crossovers
    8. 1.8 The Next Step in Hi-Fi
    9. 1.9 Active Crossover Systems
    10. 1.10 Matching Crossovers and Loudspeakers
    11. 1.11 A Modest Proposal: Popularising Active Crossovers
    12. 1.12 Multi-Way Connectors
    13. 1.13 Subjectivism
    14. References
  10. Chapter 2: How Loudspeakers Work
    1. 2.1 Sealed Box Loudspeakers
    2. 2.2 Reflex (Ported) Loudspeakers
    3. 2.3 Auxiliary Bass Radiator (ABR) Loudspeakers
    4. 2.4 Transmission Line Loudspeakers
    5. 2.5 Horn Loudspeakers
    6. 2.6 Diffraction
    7. 2.7 Modulation Distortion
    8. Further Reading
    9. References
  11. Chapter 3: Crossover Requirements
    1. 3.1 General Crossover Requirements
      1. 3.1.1 Adequate Flatness of Summed Amplitude/Frequency Response On-Axis
      2. 3.1.2 Sufficiently Steep Rolloff Slopes between the Filter Outputs
      3. 3.1.3 Acceptable Polar Response
      4. 3.1.4 Acceptable Phase Response
      5. 3.1.5 Acceptable Group Delay Behaviour
    2. 3.2 Further Requirements for Active Crossovers
      1. 3.2.1 Negligible Extra Noise
      2. 3.2.2 Negligible Impairment of System Headroom
      3. 3.2.3 Negligible Extra Distortion
      4. 3.2.4 Negligible Impairment of Frequency Response
      5. 3.2.5 Negligible Impairment of Reliability
    3. 3.3 Linear Phase
    4. 3.4 Minimum Phase
    5. 3.5 Absolute Phase
    6. 3.6 Phase Perception
    7. 3.7 Target Functions
    8. References
  12. Chapter 4: Crossover Types
    1. 4.1 All-Pole and Non-All-Pole Crossovers
    2. 4.2 Symmetric and Asymmetric Crossovers
    3. 4.3 All-Pass and Constant-Power Crossovers
    4. 4.4 Constant-Voltage Crossovers
    5. 4.5 First-Order Crossovers
      1. 4.5.1 First-Order Solen Split Crossover
      2. 4.5.2 First-Order Crossovers: 3-Way
    6. 4.6 Second-Order Crossovers
      1. 4.6.1 Second-Order Butterworth Crossover
      2. 4.6.2 Second-Order Linkwitz–Riley Crossover
      3. 4.6.3 Second-Order Bessel Crossover
      4. 4.6.4 Second-Order 1.0 dB-Chebyshev Crossover
    7. 4.7 Third-Order Crossovers
      1. 4.7.1 Third-Order Butterworth Crossover
      2. 4.7.2 Third-Order Linkwitz–Riley Crossover
      3. 4.7.3 Third-Order Bessel Crossover
      4. 4.7.4 Third-Order 1.0 dB-Chebyshev Crossover
    8. 4.8 Fourth-Order Crossovers
      1. 4.8.1 Fourth-Order Butterworth Crossover
      2. 4.8.2 Fourth-Order Linkwitz–Riley Crossover
      3. 4.8.3 Fourth-Order Bessel Crossover
      4. 4.8.4 Fourth-Order 1.0 dB-Chebyshev Crossover
      5. 4.8.5 Fourth-Order Linear-Phase Crossover
      6. 4.8.6 Fourth-Order Gaussian Crossover
      7. 4.8.7 Fourth-Order Legendre Crossover
    9. 4.9 Higher-Order Crossovers
    10. 4.10 Determining Frequency Offsets
    11. 4.11 Summary of Crossover Properties
    12. 4.12 Filler-Driver Crossovers
    13. 4.13 The Duelund Crossover
    14. 4.14 Crossover Topology
    15. 4.15 Crossover Conclusions
    16. References
  13. Chapter 5: Notch Crossovers
    1. 5.1 Elliptical Filter Crossovers
    2. 5.2 Neville Thiele MethodTM (NTM) Crossovers
    3. References
  14. Chapter 6: Subtractive Crossovers
    1. 6.1 Subtractive Crossovers
      1. 6.1.1 First-Order Subtractive Crossovers
      2. 6.1.2 Second-Order Butterworth Subtractive Crossovers
      3. 6.1.3 Third-Order Butterworth Subtractive Crossovers
      4. 6.1.4 Fourth-Order Butterworth Subtractive Crossovers
    2. 6.2 Subtractive Crossovers with Time Delays
    3. 6.3 Performing the Subtraction
    4. References
  15. Chapter 7: Lowpass & Highpass Filter Characteristics
    1. 7.1 Active Filters
    2. 7.2 Lowpass Filters
    3. 7.3 Highpass Filters
    4. 7.4 Bandpass Filters
    5. 7.5 Notch Filters
    6. 7.6 Allpass Filters
    7. 7.7 The Order of a Filter
    8. 7.8 Filter Cutoff Frequencies and Characteristic Frequencies
    9. 7.9 First-Order Filters
    10. 7.10 Second-Order and Higher-Order Filters
    11. 7.11 Filter Characteristics
      1. 7.11.1 Butterworth Filters
      2. 7.11.2 Linkwitz–Riley Filters
      3. 7.11.3 Bessel Filters
      4. 7.11.4 Chebyshev Filters
      5. 7.11.5 1 dB-Chebyshev Lowpass Filter
      6. 7.11.6 3 dB-Chebyshev Lowpass Filter
    12. 7.12 Higher-Order Filters
      1. 7.12.1 Butterworth Filters Up to Eighth-Order
      2. 7.12.2 Linkwitz–Riley Filters Up to Eighth-Order
      3. 7.12.3 Bessel Filters Up to Eighth-Order
      4. 7.12.4 Chebyshev Filters Up to Eighth-Order
    13. 7.13 More Complex Filters—Adding Zeros
      1. 7.13.1 Inverse Chebyshev Filters (Chebyshev Type II)
      2. 7.13.2 Elliptical Filters (Cauer Filters)
    14. 7.14 Some Lesser-Known Filter Characteristics
      1. 7.14.1 Transitional Filters
      2. 7.14.2 Linear-Phase Filters
      3. 7.14.3 Gaussian Filters
      4. 7.14.4 Legendre–Papoulis Filters
      5. 7.14.5 Synchronous Filters
    15. 7.15 Other Filter Characteristics
    16. References
  16. Chapter 8: Designing Lowpass and Highpass Filters
    1. 8.1 Designing Real Filters
    2. 8.2 Component Sensitivity
    3. 8.3 First-Order Lowpass and Highpass Filters
    4. 8.4 Second-Order Filters
    5. 8.5 Sallen & Key Second-Order Filters
    6. 8.6 Sallen & Key Lowpass Filter Components
    7. 8.7 Sallen & Key Second-Order Lowpass: Unity Gain
    8. 8.8 Sallen & Key Second-Order Lowpass Unity-Gain: Component Sensitivity
    9. 8.9 Sallen & Key Second-Order Lowpass: Equal-Capacitor
    10. 8.10 Sallen & Key Second-Order Lowpass Equal-C: Component Sensitivity
    11. 8.11 Sallen & Key Second-Order Butterworth Lowpass: Defined Gains
    12. 8.12 Sallen & Key Second-Order Lowpass: Non-Equal Resistors
    13. 8.13 Sallen & Key Third-Order Lowpass in a Single Stage
    14. 8.14 Sallen & Key Third-Order Lowpass in a Single Stage: Non-Equal Resistors
    15. 8.15 Sallen & Key Fourth-Order Lowpass in a Single Stage
    16. 8.16 Sallen & Key Fourth-Order Lowpass in a Single Stage: Non-Equal Resistors
    17. 8.17 Sallen & Key Fifth- and Sixth-Order Lowpass in a Single Stage
    18. 8.18 Sallen & Key Highpass Filters
    19. 8.19 Sallen & Key Second-Order Highpass: Unity Gain
    20. 8.20 Sallen & Key Second-Order Highpass: Equal-Resistors
    21. 8.21 Sallen & Key Second-Order Butterworth Highpass: Defined Gains
    22. 8.22 Sallen & Key Second-Order Highpass: Non-Equal Capacitors
    23. 8.23 Sallen & Key Third-Order Highpass in a Single Stage
    24. 8.24 Sallen & Key Fourth-Order Highpass in a Single Stage
    25. 8.25 Implementing Linkwitz–Riley with Sallen & Key Filters: Loading Effects
    26. 8.26 Lowpass Filters with Attenuation
    27. 8.27 Bandwidth Definition Filters
      1. 8.27.1 Bandwidth Definition: Butterworth versus Bessel Ultrasonic Filters
      2. 8.27.2 Bandwidth Definition: Subsonic Filters
      3. 8.27.3 Bandwidth Definition: Combined Ultrasonic and Subsonic Filters
    28. 8.28 Distortion in Sallen & Key Filters: Highpass
    29. 8.29 Distortion in Sallen & Key Filters: Lowpass
    30. 8.30 Mixed Capacitors in Low-Distortion Sallen & Key Filters
    31. 8.31 Noise in Sallen & Key Filters: Lowpass
    32. 8.32 Noise in Sallen & Key Filters: Highpass
    33. 8.33 Multiple-Feedback Filters
    34. 8.34 Multiple-Feedback Lowpass Filters
    35. 8.35 Multiple-Feedback Highpass Filters
    36. 8.36 Distortion in Multiple-Feedback Filters: Highpass
    37. 8.37 Distortion in Multiple-Feedback Filters: Lowpass
    38. 8.38 Noise in Multiple-Feedback Filters: Highpass
    39. 8.39 Noise in Multiple-Feedback Filters: Lowpass
    40. 8.40 State-Variable Filters
    41. 8.41 Variable-Frequency Filters: Sallen and Key
    42. 8.42 Variable-Frequency Filters: State-Variable Second Order
    43. 8.43 Variable-Frequency Filters: State-Variable Fourth Order
    44. 8.44 Variable-Frequency Filters: Other Orders
    45. References
  17. Chapter 9: Bandpass & Notch Filters
    1. 9.1 Multiple-Feedback Bandpass Filters
    2. 9.2 High-Q Bandpass Filters
    3. 9.3 Notch Filters
    4. 9.4 The Twin-T Notch Filter
      1. 9.4.1 The 1-Bandpass Notch Filter
      2. 9.4.2 The Bainter Notch Filter
      3. 9.4.3 The Bridged-Differentiator Notch Filter
      4. 9.4.4 Boctor Notch Filters
      5. 9.4.5 Other Notch Filters
      6. 9.4.6 Simulating Notch Filters
    5. References
  18. Chapter 10: Time Domain Filters
    1. 10.1 The Requirement for Delay Compensation
    2. 10.2 Calculating the Required Delays
    3. 10.3 Signal Summation
    4. 10.4 Physical Methods of Delay Compensation
    5. 10.5 Delay Filter Technology
    6. 10.6 Sample Crossover and Delay Filter Specification
    7. 10.7 Allpass Filters in General
      1. 10.7.1 First-Order Allpass Filters
      2. 10.7.2 Second-Order Allpass Filters
      3. 10.7.3 Third-Order Allpass Filters
      4. 10.7.4 Higher-Order Filters
    8. 10.8 Delay Lines for Subtractive Crossovers
    9. 10.9 Variable Allpass Time Delays
    10. 10.10 Lowpass Filters for Time Delays
    11. References
  19. Chapter 11: Equalisation
    1. 11.1 The Need for Equalisation
    2. 11.2 What Equalisation Can and Can’t Do
    3. 11.3 Loudspeaker Equalisation
      1. 11.3.1 Drive Unit Equalisation
      2. 11.3.2 6 dB/oct Dipole Equalisation
      3. 11.3.3 Bass Response Extension
      4. 11.3.4 Diffraction Compensation Equalisation
      5. 11.3.5 Room Interaction Correction
    4. 11.4 Equalisation Circuits
    5. 11.5 HF-Boost and LF-Cut Equaliser
    6. 11.6 HF-Cut and LF-Boost Equaliser
    7. 11.7 Combined HF-Boost and HF-Cut Equaliser
    8. 11.8 Adjustable Peak/Dip Equalisers: Fixed Frequency and Low Q
    9. 11.9 Adjustable Peak/Dip Equalisers: Variable Centre Frequency and Low Q
    10. 11.10 Adjustable Peak/Dip Equalisers with High Q
    11. 11.11 The Bridged-T Equaliser
    12. 11.12 The Biquad Equaliser
    13. 11.13 Capacitance Multiplication for the Biquad Equaliser
    14. 11.14 Equalisers with Non-6 dB Slopes
    15. 11.15 Equalisation by Filter Frequency Offset
    16. 11.16 Equalisation by Adjusting All Filter Parameters
    17. References
  20. Chapter 12: Passive Components for Active Crossovers
    1. 12.1 Resistors: Values and Tolerances
    2. 12.2 Improving Accuracy with Multiple Components: Gaussian Distribution
    3. 12.3 Resistor Value Distributions
    4. 12.4 Improving Accuracy with Multiple Components: Uniform Distribution
    5. 12.5 Obtaining Arbitrary Resistance Values
    6. 12.6 Resistor Noise: Johnson and Excess Noise
    7. 12.7 Resistor Non-Linearity
    8. 12.8 Capacitors: Values and Tolerances
    9. 12.9 Capacitor Shortcomings
    10. 12.10 Non-Electrolytic Capacitor Non-Linearity
    11. 12.11 Electrolytic Capacitor Non-Linearity
    12. References
  21. Chapter 13: Opamps for Active Crossovers
    1. 13.1 Active Devices for Active Crossovers
    2. 13.2 Opamp Types
      1. 13.2.1 Opamp Properties: Noise
      2. 13.2.2 Opamp Properties: Slew Rate
      3. 13.2.3 Opamp Properties: Common-Mode Range
      4. 13.2.4 Opamp Properties: Input Offset Voltage
      5. 13.2.5 Opamp Properties: Bias Current
      6. 13.2.6 Opamp Properties: Cost
      7. 13.2.7 Opamp Properties: Internal Distortion
      8. 13.2.8 Opamp Properties: Slew-Rate Limiting Distortion
      9. 13.2.9 Opamp Properties: Distortion Due to Loading
      10. 13.2.10 Opamp Properties: Common-Mode Distortion
    3. 13.3 Opamps Surveyed
    4. 13.4 The TL072 Opamp
    5. 13.5 The NE5532 and NE5534 Opamps
    6. 13.6 The 5532 with Shunt Feedback
    7. 13.7 5532 Output Loading in Shunt-Feedback Mode
    8. 13.8 The 5532 with Series Feedback
    9. 13.9 Common-Mode Distortion in the 5532
    10. 13.10 Reducing 5532 Distortion by Output Biasing
    11. 13.11 Which 5532?
    12. 13.12 The 5534 Opamp
    13. 13.13 The LM4562 Opamp
    14. 13.14 Common-Mode Distortion in the LM4562
    15. 13.15 The LME49990 Opamp
    16. 13.16 Common-Mode Distortion in the LME49990
    17. 13.17 The AD797 Opamp
    18. 13.18 Common-Mode Distortion in the AD797
    19. 13.19 The OP27 Opamp
    20. 13.20 Opamp Selection
    21. References
  22. Chapter 14: Active Crossover System Design
    1. 14.1 Crossover Features
      1. 14.1.1 Input Level Controls
      2. 14.1.2 Subsonic Filters
      3. 14.1.3 Ultrasonic Filters
      4. 14.1.4 Output Level Trims
      5. 14.1.5 Output Mute Switches, Output Phase-Reverse Switches
      6. 14.1.6 Control Protection
    2. 14.2 Features Usually Absent
      1. 14.2.1 Metering
      2. 14.2.2 Relay Output Muting
      3. 14.2.3 Switchable Crossover Modes
    3. 14.3 Noise, Headroom, and Internal Levels
    4. 14.4 Circuit Noise and Low-Impedance Design
    5. 14.5 Using Raised Internal Levels
    6. 14.6 Placing the Output Attenuator
    7. 14.7 The Amplitude/Frequency Distribution of Musical Signals and Internal Levels
    8. 14.8 Gain Structures
    9. 14.9 Noise Gain
    10. 14.10 Active Gain-Controls
    11. 14.11 Filter Order in the Signal Path
    12. 14.12 Output Level Controls
    13. 14.13 Mute Switches
    14. 14.14 Phase-Invert Switches
    15. 14.15 Distributed Peak Detection
    16. 14.16 Power Amplifier Considerations
    17. References
  23. Chapter 15: Subwoofer Crossovers
    1. 15.1 Subwoofer Applications
    2. 15.2 Subwoofer Technologies
      1. 15.2.1 Sealed-Box (Infinite Baffle) Subwoofers
      2. 15.2.2 Reflex (Ported) Subwoofers
      3. 15.2.3 Auxiliary Bass Radiator (ABR) Subwoofers
      4. 15.2.4 Transmission Line Subwoofers
      5. 15.2.5 Bandpass Subwoofers
      6. 15.2.6 Isobaric Subwoofers
      7. 15.2.7 Dipole Subwoofers
      8. 15.2.8 Horn-Loaded Subwoofers
    3. 15.3 Subwoofer Drive Units
    4. 15.4 Hi-fi Subwoofers
    5. 15.5 Home Entertainment Subwoofers
      1. 15.5.1 Low-Level Inputs (Unbalanced)
      2. 15.5.2 Low-Level Inputs (Balanced)
      3. 15.5.3 High-Level Inputs
      4. 15.5.4 High-Level Outputs
      5. 15.5.5 Mono Summing
      6. 15.5.6 LFE Input
      7. 15.5.7 Level Control
      8. 15.5.8 Crossover In/Out Switch
      9. 15.5.9 Crossover Frequency Control (Lowpass Filter)
      10. 15.5.10 Highpass Subsonic Filter
      11. 15.5.11 Phase Switch (Normal/Inverted)
      12. 15.5.12 Variable Phase Control
      13. 15.5.13 Signal Activation Out of Standby
    6. 15.6 Home Entertainment Crossovers
      1. 15.6.1 Fixed Frequency
      2. 15.6.2 Variable Frequency
      3. 15.6.3 Multiple Variable
    7. 15.7 Power Amplifiers for Home Entertainment Subwoofers
    8. 15.8 Subwoofer Integration
    9. 15.9 Sound Reinforcement Subwoofers
      1. 15.9.1 Line or Area Arrays
      2. 15.9.2 Cardioid Subwoofer Arrays
      3. 15.9.3 Aux-Fed Subwoofers
    10. 15.10 Automotive Audio Subwoofers
    11. References
  24. Chapter 16: Line Inputs and Outputs
    1. 16.1 External Signal Levels
    2. 16.2 Internal Signal Levels
    3. 16.3 Input Amplifier Functions
    4. 16.4 Unbalanced Inputs
    5. 16.5 Balanced Interconnections
    6. 16.6 The Advantages of Balanced Interconnections
    7. 16.7 The Disadvantages of Balanced Interconnections
    8. 16.8 Balanced Cables and Interference
      1. 16.8.1 Electrostatic Coupling
      2. 16.8.2 Magnetic Coupling
      3. 16.8.3 Ground Voltages
    9. 16.9 Balanced Connectors
    10. 16.10 Balanced Signal Levels
    11. 16.11 Electronic versus Transformer Balanced Inputs
    12. 16.12 Common Mode Rejection Ratio (CMRR)
    13. 16.13 The Basic Electronic Balanced Input
      1. 16.13.1 Case 1
      2. 16.13.2 Case 2
      3. 16.13.3 Case 3
      4. 16.13.4 Case 4
      5. 16.13.5 Case 5
    14. 16.14 Common-Mode Rejection Ratio: Opamp Gain
    15. 16.15 Common-Mode Rejection Ratio: Opamp Frequency Response
    16. 16.16 Common-Mode Rejection Ratio: Opamp CMRR
    17. 16.17 Common-Mode Rejection Ratio: Amplifier Component Mismatches
    18. 16.18 A Practical Balanced Input
    19. 16.19 Variations on the Balanced Input Stage
    20. 16.20 Combined Unbalanced and Balanced Inputs
    21. 16.21 The Superbal Input
    22. 16.22 Switched Gain Balanced Inputs
    23. 16.23 Variable-Gain Balanced Inputs
    24. 16.24 High Input Impedance Balanced Inputs
    25. 16.25 The Instrumentation Amplifier
    26. 16.26 Transformer Balanced Inputs
    27. 16.27 Input Overvoltage Protection
    28. 16.28 Noise and Balanced Inputs
    29. 16.29 Low-Noise Balanced Inputs
    30. 16.30 Low-Noise Balanced Inputs in Real Life
    31. 16.31 Ultra-Low-Noise Balanced Inputs
    32. References
  25. Chapter 17: Line Outputs
    1. 17.1 Unbalanced Outputs
    2. 17.2 Zero-Impedance Outputs
    3. 17.3 Ground-Cancelling Outputs
    4. 17.4 Balanced Outputs
    5. 17.5 Transformer Balanced Outputs
    6. 17.6 Output Transformer Frequency Response
    7. 17.7 Transformer Distortion
    8. 17.8 Reducing Transformer Distortion
    9. References
  26. Chapter 18: Power Supply Design
    1. 18.1 Opamp Supply Rail Voltages
    2. 18.2 Designing a ±15 V Supply
    3. 18.3 Designing a ±17 V Supply
    4. 18.4 Using Variable-Voltage Regulators
    5. 18.5 Improving Ripple Performance
    6. 18.6 Dual Supplies from a Single Winding
    7. 18.7 Mutual Shutdown Circuitry
    8. 18.8 Power Supplies for Discrete Circuitry
    9. Reference
  27. Chapter 19: An Active Crossover Design
    1. 19.1 Design Principles
    2. 19.2 Example Crossover Specification
    3. 19.3 The Gain Structure
    4. 19.4 Resistor Selection
    5. 19.5 Capacitor Selection
    6. 19.6 The Balanced Line Input Stage
    7. 19.7 The Bandwidth Definition Filter
    8. 19.8 The HF Path: 3 kHz Linkwitz–Riley Highpass Filter
    9. 19.9 The HF Path: Time Delay Compensation
    10. 19.10 The MID Path: Topology
    11. 19.11 The MID Path: 400 Hz Linkwitz–Riley Highpass Filter
    12. 19.12 The MID Path: 3 kHz Linkwitz–Riley Lowpass Filter
    13. 19.13 The MID Path: Time Delay Compensation
    14. 19.14 The LF Path: 400 Hz Linkwitz–Riley Lowpass Filter
    15. 19.15 The LF Path: No Time Delay Compensation
    16. 19.16 Output Attenuators and Level Trim Controls
    17. 19.17 Balanced Outputs
    18. 19.18 Crossover Programming
    19. 19.19 Noise Analysis: Input Circuitry
    20. 19.20 Noise Analysis: HF Path
    21. 19.21 Noise Analysis: MID Path
    22. 19.22 Noise Analysis: LF Path
    23. 19.23 Improving the Noise Performance: The MID Path
    24. 19.24 Improving the Noise Performance: The Input Circuitry
    25. 19.25 The Noise Performance: Comparisons with Power Amplifier Noise
    26. 19.26 Conclusion
    27. Reference
  28. Appendix 1 Crossover Design References
  29. Appendix 2 Loudspeaker Design References
  30. Index