Sound Systems: Design and Optimization

Transcription

1 Sound Systems: Design and Optimization Modern techniques and tools for sound System design and alignment Bob McCarthy ELSEVIER AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO Focal Press is an imprint of Elsevier

2 Preface Acknowledgements SECTION 1: SOUND SYSTEMS 1. Transmission Transmission Goals Audio Transmission Defined Time and Frequency Wavelength The Waveform Transmission Quantified Decibels Power Frequency Response Polarity Latency Analog Audio Transmission Line Level Devices Line Level Interconnection Speaker Level Devices Power Amplifiers ix xvi Speaker Level Interconnection Speaker Cables 40 Digital Audio Transmission 42 Digital Audio Devices 42 Digital Audio Interconnection 43 Acoustic Transmission Power, Pressure and Surface Area Environmental Effects: Humidity and Temperature Acoustic Transmitters: Loudspeakers Reference Summation Overview Properties of Audio Summation Audio Summation Defined Summation Criteria Summation Quantity Electrical vs. Acoustical Summation Acoustical Source Direction Summation Math Summation Amplitude Summation Phase Response Ripple Summation Zones Comb Filtering: Linear vs. Log Summation Geometry Acoustical Crossovers Acoustic Crossover Defined Crossover Classes V

3 Spectral Dividers and Spectral Crossovers 89 Spatial Dividers and Spatial Crossovers 101 Speaker Arrays 112 Introduction 112 Speaker Array Types 112 Coupled Arrays 115 Uncoupled Arrays 125 Speaker/Room Summation 140 Analogous Functions 140 Speaker/Room Summation Types 143 Absorption Effects 147 Environmental Effects Reception 150 Introduction 150 Loudness 151 Loudness and db SPL 151 The Equal Loudness Contours 152 Localization 153 Introduction 153 Sonic Image 153 Vertical Localization 154 Front/Back Localization 157 Horizontal Localization 157 Tonal, Spatial and Echo Perception 164 Introduction 164 Tonal Perception 165 Echo Perception 167 Spatial Perception 168 Perception Zone Detection 169 Stereo Perception 169 Introduction 169 Panoramic Field 170 Stereo Scaling 171 Stereo Side-Effects 175 Amplified Sound Detection 176 Distortion 176 Compression 176 Frequency Response Coloration 176 False Perspective 176 Microphone Reception 178 Introduction 178 Comparing Microphones to Our Ears 178 Measurement Microphones 179 References 180 CTION 2: DESIGN 181 Evaluation 183 Introduction 183 Natural Sound vs. Amplified Sound 184 Contrasting Emission, Transmission and Reception Models 185 Transmission Path Differences 186 Relating the Worlds of Acousticians and Audio Engineers 1 Comparing Our Goals 1 The Middle Ground 8 Moving Forward 201 Reference 205 Prediction 206 Introduction 206 Drawings D Drawing Types D Drawing Types D Drawings in a 3-D World 208 Scale 212 Acoustic Modeling Programs 212 Introduction 212 A Very Brief History 213 Speaker Data Files 214 Acoustic Transmission Properties 220 Material Absorption Properties 225 Characterizing Summations 226 Applications 229 Conclusions 230 Variation 232 Introduction 232 The Minimum Variance Principles 235 Variation Defined 235 Causes and Standard Progressions of Variance 235 Minimum Variance vs. Maximum SPL 242

4 The Speaker/Room Link: Aspect Ratio Protractors and Pizza Maximum Acceptable Variance Asymmetrie Coverage Considerations The Coverage Bow Method The Forward Aspect Ratio The Proximity Ratio Minimum Level Variance Single Speakers Coupled Speaker Arrays Uncoupled Speaker Arrays Minimum Spectral Variance Relating Aspect Ratio, Beamwidth and Speaker Order Speaker Array Methods Minimum Ripple Variance Subwoofer Arrays End Fire Two-Element In-Line Technique Inverted Stack Coupled and Uncoupled Line Source Coupled and Uncoupled Point Source Conclusion Speaker Order and Beamwidth Maximum Power vs. Minimum Variance Minimum Variance Coverage Shapes Specification Introduction The Principles of Specification Specification Defined Goals and Challenges Specific Questions Specific Answers Compromise Channel/System Types Mono Stereo Surround Source Effects System Subdivision Subsystem Types Main Systems 325 Sidefill 327 Infill 327 Downfill 328 Frontfill 328 Delays 328 The Scalable Design 330 Scaling for Power 330 Overlapping for Power 330 Scaling the Shape 331 Array Design Procedures 331 Main System Design 331 Symmetrie Coupled Point Source 332 Asymmetrie Coupled Point Source 333 Asymmetric-Composite Coupled Point Source 337 Symmetrie Uncoupled Line Source 341 Asymmetrie Uncoupled Line Source 342 Symmetrie Uncoupled Point Source 342 Asymmetrie Uncoupled Point Source 342 Symmetrie Uncoupled Point Destination 342 Asymmetrie Uncoupled Point Destination 343 The Diagonal Plane 343 Balcony Battles 346 Multichannel Sound 350 SECTION 3: OPTIMIZATION Examination Examination Defined Physical Measurement Tools Inclinometer Protractor Origami Angle Finder Laser Pointer Thermometer Hygrometer Simple Audio Measurement Tools Volt/ohm meter (VOM) Polarity Tester Listen Box Impedance Tester

5 10. Oscilloscope Sound Level Meter Real-Time Analyzer (RTA) Complex Audio Measurement Tools The Fourier Transform Analyzer Basics Signal Averaging Single-Channel Spectrum Applications Transfer Function Measurement Other Complex Signal Analyzers Analysis Systems Reference Verification Introduction Test Structure Testing Stages Access Points Test Setup Procedures Noise Over Frequency Total Harmonie Distortion + Noise (THD + n Maximum Input/Output Capability Over Frequency Latency Polarity Frequency Response Phase Response over Frequency Compression Microphone Verification Microphone Match Microphone Response Post-Calibration Verification Additional Considerations Calibration Calibration Defined Goals Challenges Strategies Techniques ) Approaches to Calibration Anarchy Monarchy Capitalism Democracy TANSTAAFL and Triage Access to Information Calibration Subdivision Physical Access Electronic Access Acoustic Access Microphone Position Strategies Procedures Acoustic Evaluation Level Setting Speaker Position Adjustment Equalization Delay Setting Order of Operations Practical Applications Finishing the Process Listening Ongoing Optimization Using Program Material as the Source Audience Presence Temperature and Humidity Stage Leakage Stage Microphone Summation Feedback Multichannel Program Material Show Mic Positions Subwoofers as a Program Channel Final Word Afterword Glossary Bibliograph]/ Index