Electroacoustic Devices: Microphones and Loudspeakers This page intentionally left blank Electroacoustic Devices: Microphones and Loudspeakers Edited by Glen Ballou AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Focal Press is an imprint of Elsevier Focal Press is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA Linacre House, Jordan Hill, Oxford OX2 8DP, UK © 2009 ELSEVIER Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. 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To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data Application submitted British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ISBN: 978-0-240-81267-0 For information on all Focal Press publications visit our website at www.elsevierdirect.com Typeset by: diacriTech, Chennai, India 09 10 11 12 5 4 3 2 1 Printed in the United States of America Contents Part I Electroacoustic Devices 1. Microphones Glen Ballou, Joe Ciaudelli, Volker Schmitt 1.1 Introduction 4 1.2 Pickup Patterns 5 1.2.1 Omnidirectional Microphones 5 1.2.2 Bidirectional Microphones 9 1.2.3 Unidirectional Microphones 10 1.3 Types of Transducers 23 1.3.1 Carbon Microphones 23 1.3.2 Crystal and Ceramic Microphones 24 1.3.3 Dynamic Microphones 26 1.3.4 Capacitor Microphones 33 1.3.5 Electret Microphones 48 1.4 Microphone Sensitivity 49 1.4.1 Open-Circuit Voltage Sensitivity 49 1.4.2 Maximum Power Output Sensitivity 50 1.4.3 Electronic Industries Association (EIA) Output Sensitivity 51 1.4.4 Various Microphone Sensitivities 53 1.4.5 Microphone Thermal Noise 53 1.5 Microphone Practices 54 1.5.1 Placement 54 1.5.2 Grounding 56 1.5.3 Polarity 57 1.5.4 Balanced or Unbalanced 59 1.5.5 Impedance 59 1.6 Miscellaneous Microphones 61 1.6.1 Pressure Zone Microphones (PZM) 61 1.6.2 Lavalier Microphones 69 1.6.3 Head-Worn Microphones 72 1.6.4 Base Station Microphones 75 1.6.5 Differential Noise-Canceling Microphones 76 1.6.6 Controlled-Reluctance Microphones 77 1.6.7 Handheld Entertainer Microphones 77 1.6.8 Pressure-Gradient Condenser Microphones 79 1.6.9 Interference Tube Microphones 82 1.6.10 Rifle Microphones 89 1.6.11 Parabolic Microphones 90 v vi Contents 1.6.12 Zoom Microphones 91 1.6.13 Automatic Microphone Systems 94 1.6.14 PolarFlex™ Microphone System 95 1.7 Stereo Microphones 98 1.7.1 Coincident Microphones 98 1.7.2 XY Stereo Technique 100 1.7.3 The ORTF Technique 103 1.7.4 The M/S Stereo Technique 104 1.7.5 The Stereo Boom Microphone 111 1.7.6 SASS Microphones 113 1.7.7 Surround Sound Microphone System 115 1.8 Microphones for Binaural Recording 120 1.8.1 Artificial Head Systems 120 1.8.2 In the Ear Recording Microphones 124 1.9 USB Microphones 126 1.10 Wireless Communication Systems 127 1.10.1 Criteria for Selecting a Wireless Microphone 129 1.10.2 Receiving Antenna Systems 134 1.10.3 Companding 137 1.10.4 Waterproof Wireless Microphone Systems 138 1.11 Multichannel Wireless Microphone and Monitoring Systems 139 1.11.1 Introduction 139 1.11.2 Frequencies 140 1.11.3 Spacing 140 1.11.4 Frequency Deviation 140 1.11.5 Frequency Coordination 140 1.11.6 Transmitter Considerations 143 1.11.7 Receiver Considerations 146 1.11.8 Antennas 147 1.11.9 Wireless Monitor Systems 151 1.11.10 System Planning for Multichannel Wireless Systems 152 1.11.11 Future Considerations: Digital Wireless Transmission 154 1.11.12 Conclusion 155 1.12 Microphone Accessories 156 1.12.1 Inline Microphone Processors 156 1.12.2 Windscreens and Pop Filters 160 1.12.3 Shock Mounts 165 1.12.4 Stands and Booms 169 1.12.5 Attenuators and Equalizers 170 1.13 Microphone Techniques 171 1.13.1 Stereo Micing Techniques 173 1.13.2 Microphone Choice 174 1.13.3 Microphone Characteristics 174 1.13.4 Specific Micing Techniques 176 1.13.5 Conclusion 192 Acknowledgments 192 References 192 Bibliography 193 Contents vii 2. Loudspeakers Jay Mitchell 2.1 Introduction 196 2.1.1 Uses of Loudspeakers 196 2.1.2 Loudspeaker Components 197 2.2 Transducer Types 197 2.2.1 Electrodynamic Transducers 198 2.2.2 Diaphragm Types 199 2.2.3 Suspension Methods 201 2.2.4 Mechanical Construction 201 2.3 Compression Drivers 203 2.4 Electrostatic Transducers 206 2.5 Piezoelectric Loudspeakers 210 2.6 Motor Design Considerations 213 2.6.1 Output Limitations 215 2.6.2 Heat Transfer Designs for High-Power Woofers 219 2.7 Radiator Types 221 2.7.1 Direct Radiators 221 2.7.2 Cone Radiators 221 2.7.3 Dome Radiators 222 2.7.4 Ring Radiators 222 2.7.5 Panel Radiators 223 2.7.6 Horns 223 2.8 Loudspeaker Systems 234 2.8.1 Configuration Choices 235 2.8.2 Types of Loudspeaker Systems 236 2.8.3 Performance Issues in Multiway Systems 237 2.8.4 Line Arrays 241 2.8.5 Crossovers 243 2.8.6 Acoustic Boundaries 249 2.8.7 Conclusion 251 2.9 Characterization of Loudspeaker Performance 252 2.9.1 Motivation 252 2.9.2 Efficiency and Sensitivity 252 2.9.3 Network Transfer Function 253 2.9.4 Loudspeaker Transfer Function 253 2.9.5 Impedance 255 2.9.6 Distortion 257 2.9.7 Characterization for Design Purposes 257 2.9.8 Characterization for the User 258 2.10 Direct Radiation of Sound 261 2.10.1 Acoustics of Radiators 261 2.10.2 Direct Radiator Enclosure Design 265 2.10.3 Horns 270 2.11 Loudspeaker Testing and Measurement 271 2.11.1 Linear Transfer Function 271 2.11.2 Chart Recorders 272 viii Contents 2.11.3 Real Time Analyzers 273 2.11.4 Time-Windowed Measurements 274 2.11.5 Swept Sine Measurements 276 Reference 277 Bibliography 277 3. Loudspeaker Cluster Design Ralph Heinz 3.1 Why Array? 279 3.2 Array Problems and Partial Solutions: A Condensed History 280 3.3 Conventional Array Shortcomings 280 3.4 Conventional Array Shortcoming Analysis 284 3.5 Coincident Acoustical Centers: A Practical Approach 286 3.5.1 TRAP Horns: A New Approach 286 3.5.2 TRAP Performance 289 3.6 Low Frequency Arrays: Beneficial Interference 289 3.6.1 Horizontal Woofer Arrays: Maintaining Wide Dispersion 289 3.6.2 Vertical Woofer Arrays 291 3.7 Line Arrays and Digitally Steerable Loudspeaker Column Arrays 292 3.7.1 What Affects Intelligibility 293 3.7.2 Measuring Intelligibility 294 3.7.3 Architecture and Room Acoustics 295 3.7.4 Line Arrays 296 3.7.5 DSP-Driven Vertical Arrays 300 3.7.6 Multichannel DSP Can Control Array Height 306 3.7.7 Steerable Arrays May Look Like Columns But They Are Not 306 Index 311 Part I Electroacoustic Devices This page intentionally left blank Section 1 Microphones Glen Ballou, Joe Ciaudelli, Volker Schmitt 1.1 Introduction 1.5.3 Polarity 1.2 Pickup Patterns 1.5.4 Balanced or Unbalanced 1.2.1 Omnidirectional 1.5.5 Impedance Microphones 1.6 Miscellaneous Microphones 1.2.2 Bidirectional 1.6.1 Pressure Zone Microphones Microphones (PZM) 1.2.3 Unidirectional 1.6.2 Lavalier Microphones Microphones 1.6.3 Head-Worn 1.3 Types of Transducers Microphones 1.3.1 Carbon Microphones 1.6.4 Base Station Microphones 1.3.2 Crystal and Ceramic 1.6.5 Differential Noise- Microphones Canceling Microphones 1.3.3 Dynamic Microphones 1.6.6 Controlled-Reluctance 1.3.4 Capacitor Microphones Microphones 1.3.5 Electret Microphones 1.6.7 Handheld Entertainer 1.4 Microphone Sensitivity Microphones 1.4.1 Open-Circuit Voltage 1.6.8 Pressure-Gradient Sensitivity Condenser Microphones 1.4.2 Maximum Power Output 1.6.9 Interference Tube Sensitivity Microphones 1.4.3 Electronic Industries 1.6.10 Rifle Microphones Association (EIA) Output 1.6.11 Parabolic Microphones Sensitivity 1.6.12 Zoom Microphones 1.4.4 Various Microphone 1.6.13 Automatic Microphone Sensitivities Systems 1.4.5 Microphone Thermal 1.6.14 PolarFlex™ Noise Microphone System 1.5 Microphone Practices 1.7 Stereo Microphones 1.5.1 Placement 1.7.1 Coincident Microphones 1.5.2 Grounding 1.7.2 XY Stereo Technique Electroacoustic Devices: Microphones and Loudspeakers Copyright © 2009 by Focal Press, Inc.