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Technical Illustrations for college textbook on the Physics of High Fidelity.

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Page 1: Technical Illustrations

Contents

1 Introduction to Hi-Fi 1

2 Waves 14

3 Decibels 63

4 Loudspeakers 67

5 Electricity 112

6 Ampli�ers 138

7 Electromagnetism 153

8 Electromagnetic Waves and Tuners 173

9 Analog Recording and Playback 202

10 Digital Optical Recording & Playback 226

11 Digital Magnetic Recording & Playback 247

12 Heat 260

13 Mechanics 273

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List of Figures

1.1 Stereo process in recording and playback. : : : : : : : : : : : 21.2 Surround sound reproduction of audio information. : : : : : : 31.3 Storage or transmission of sound in stereo. : : : : : : : : : : : 31.4 Playback process in stereo. : : : : : : : : : : : : : : : : : : : 41.5 Elements of a receiver. : : : : : : : : : : : : : : : : : : : : : : 41.6 Example of basic connections to a receiver. : : : : : : : : : : 51.7 Elements of an integrated ampli�er. : : : : : : : : : : : : : : 51.8 Connections to an integrated ampli�er. : : : : : : : : : : : : : 61.9 All separate approach. : : : : : : : : : : : : : : : : : : : : : : 61.10 Connections in all-separate approach. : : : : : : : : : : : : : 71.11 Basic A/V System. : : : : : : : : : : : : : : : : : : : : : : : : 81.12 A/V receiver driving a surround-sound system. : : : : : : : : 91.13 Details of the tape monitor switch when listening to a sound

source with available tape recording. : : : : : : : : : : : : : : 101.14 Listening to a tape; tape switch in. : : : : : : : : : : : : : : : 111.15 A/V receiver with Dolby Pro Logic processor. : : : : : : : : : 121.16 Various wave forms. : : : : : : : : : : : : : : : : : : : : : : : 13

2.1 Phono record and an enlarged groove showing engraved waverepresenting sound. : : : : : : : : : : : : : : : : : : : : : : : : 15

2.2 Simpli�ed picture of a water wave; displaced water as a func-tion of position. : : : : : : : : : : : : : : : : : : : : : : : : : : 15

2.3 Details of one wave as a function of position. : : : : : : : : : 162.4 Large and small amplitude waves. : : : : : : : : : : : : : : : : 162.5 Time dependence of displacement of a point on a water wave. 172.6 Displacement as a function of time; time required to complete

one wave. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 172.7 Transverse wave on a string. : : : : : : : : : : : : : : : : : : : 182.8 Longitudinal waves along a solid bar. : : : : : : : : : : : : : : 18

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2.9 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 182.10 Sound requires a medium in which to propagate; in a vacuum

there is no sound propagation. : : : : : : : : : : : : : : : : : 192.11 Direct radiator speaker can move air like a drumhead. : : : : 192.12 Generation of sound by loudspeaker. : : : : : : : : : : : : : : 202.13 Disturbances created by loudspeaker; pressure changes cause

sound. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 212.14 Representation of sound created by a loudspeaker. : : : : : : 212.15 Wave Y has 4 times the power of wave X, but their ampli-

tudes di�er only by a factor of 2. : : : : : : : : : : : : : : : : 222.16 Re ection of a wave by an obstacle or a di�erent medium. : : 222.17 Speaker producing a pulse of sound in a hall. : : : : : : : : : 232.18 Paths of direct and re ected sound in a hall. : : : : : : : : : : 242.19 Direct and reverberant sound in a hall. : : : : : : : : : : : : : 252.20 Direct and reverberant sound contributions to sound in a hall. 262.21 Sound radiated by a speaker; as one moves away the intensity

decreases. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 272.22 Sound intensity through surface 2 is di�erent from that of 1. : 282.23 Observer and source at rest and in relative motion. : : : : : : 292.24 Doppler E�ect produced by speaker producing simultane-

ously 100 Hz and 1,000 Hz sound waves. : : : : : : : : : : : : 302.25 Sound wave in cold air entering hot air. : : : : : : : : : : : : 312.26 Refraction of a sound wave. : : : : : : : : : : : : : : : : : : : 312.27 Above a critical angle of incidence there is only re ection. : : 322.28 Sound travels in a curved hollow plastic tube by multiple

re ections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 332.29 Sound wave produced by a musical group; a complex wave. : 342.30 Simple sine waveform. : : : : : : : : : : : : : : : : : : : : : : 342.31 Comparison between one full wave and one rotation of a circle. 352.32 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 352.33 Addition of two waves out of phase by 180 degrees. : : : : : : 352.34 Constructive interference. : : : : : : : : : : : : : : : : : : : : 362.35 Destructive interference. : : : : : : : : : : : : : : : : : : : : : 372.36 Obstacle with aperture receiving high frequency waves. : : : : 382.37 Low frequency behavior of obstacle and aperture. : : : : : : : 392.38 Comparison of di�raction behavior of a room with opening

and a loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : : 402.39 Dispersion characteristics of a speaker. : : : : : : : : : : : : : 412.40 Standing wave produced by incident and re ected waves. : : : 41

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2.41 Simplest possible standing wave on a string. : : : : : : : : : : 422.42 Simplest standing wave on a string during one cycle. : : : : : 432.43 Second harmonic on a string showing position of nodes and

antinodes. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 432.44 Third harmonic on a string clamped at both ends. : : : : : : 432.45 Setting up a standing wave in a tube. : : : : : : : : : : : : : 442.46 Simplest standing wave in a tube open at both ends. : : : : : 452.47 Second harmonic in tube open at both ends. : : : : : : : : : : 452.48 Fundamental in a tube. : : : : : : : : : : : : : : : : : : : : : 452.49 Tube open at one end excited by a tuning fork. : : : : : : : : 462.50 Fundamental in tube open at one end. : : : : : : : : : : : : : 462.51 Next more complicated standing wave; the third harmonic. : 472.52 Fifth harmonic. : : : : : : : : : : : : : : : : : : : : : : : : : : 472.53 Standing wave in a tube 1 meter long; fundamental. : : : : : 472.54 Tube closed at both ends. : : : : : : : : : : : : : : : : : : : : 482.55 Fundamental of a tube closed at both ends. : : : : : : : : : : 482.56 Room where independent standing waves can be set up in the

x, y, and z directions. : : : : : : : : : : : : : : : : : : : : : : 492.57 A drumhead �xed at its edges and its fundamental mode of

vibration. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 502.58 Overtone on a drumhead. : : : : : : : : : : : : : : : : : : : : 512.59 Standing wave pattern on a Chladni plate. : : : : : : : : : : : 512.60 Complex wave created by the superposition of a 100 Hz fun-

damental and its fourth harmonic. : : : : : : : : : : : : : : : 522.61 Violin string plucked by a �nger and producing all sorts of

harmonics. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 532.62 Complex wave generated by plucking string. : : : : : : : : : : 542.63 Square wave; it is made up of many harmonics. : : : : : : : : 552.64 Spectrum of a square wave. : : : : : : : : : : : : : : : : : : : 562.65 Sawtooth wave and its harmonic content. : : : : : : : : : : : 572.66 Spectrum of a sawtooth wave. : : : : : : : : : : : : : : : : : : 582.67 A string bowed at its middle and harmonics which are excited. 592.68 String on a piano struck by hammer at a distance 1/10 the

string length from one end. : : : : : : : : : : : : : : : : : : : 602.69 Vibrations of an object at di�erent excitation frequencies. : : 602.70 Oscillations of a mass on a spring, undamped and damped

when submersed in oil. : : : : : : : : : : : : : : : : : : : : : : 612.71 Resonance of wine glass excited by sound. : : : : : : : : : : : 61

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2.72 Beats caused by the combination of two waves with slightlydi�erent frequencies. : : : : : : : : : : : : : : : : : : : : : : : 62

3.1 Decibel meter. : : : : : : : : : : : : : : : : : : : : : : : : : : 643.2 Receiver with volume control marked in dB. : : : : : : : : : : 643.3 Response of human ears at the threshold of hearing. : : : : : 643.4 Response of human ears for various sound levels: Fletcher-

Munson curves. : : : : : : : : : : : : : : : : : : : : : : : : : : 653.5 Outer ear approximated by a tube closed at one end. : : : : : 653.6 Measuring the frequency response of a speaker. : : : : : : : : 663.7 Frequency response of a speaker. : : : : : : : : : : : : : : : : 66

4.1 Role of loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : 684.2 Distortion of spectrum of original waveform by non- at fre-

quency response of speaker. : : : : : : : : : : : : : : : : : : : 694.3 Dispersion properties of speakers. : : : : : : : : : : : : : : : : 704.4 Two low frequency waves from speaker arriving at O. : : : : : 714.5 Two high frequency waves from speaker arriving at O. : : : : 724.6 Details of waves 2 and 1 at high frequencies. : : : : : : : : : : 734.7 Sound dispersion of a driver as the frequency is increased. : : 744.8 Division of audio spectrum for a three-way loudspeaker. : : : 754.9 Net e�ect of subdividing the whole audio range into three

sections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 764.10 Subdivision of audio spectrum in a two-way system. : : : : : 764.11 Amount of sound produced depends on volume displacement.

A is louder than B. : : : : : : : : : : : : : : : : : : : : : : : : 774.12 To produce same amount of sound by both drivers at the

same frequency, the small one has to move through a largerdistance than the big one. : : : : : : : : : : : : : : : : : : : : 78

4.13 Volume of air moved by loudspeaker as a function of frequencyto produce same loudness of sound. : : : : : : : : : : : : : : : 79

4.14 Low frequency and high frequency simple pendulums doingdi�erent amounts of work per second for same amplitude ofdisplacement. : : : : : : : : : : : : : : : : : : : : : : : : : : : 80

4.15 Balance between electrical power going to driver and the pro-duction of sound power and heat dissipation by driver. : : : : 80

4.16 Example of a loudspeaker whose e�ciency is less than 100%. 814.17 Basic cone speaker. : : : : : : : : : : : : : : : : : : : : : : : : 82

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4.18 Comparison of cone-shape over at shape for mechanical strengthwhen thin material is used. : : : : : : : : : : : : : : : : : : : 83

4.19 Modeling of diaphragm action by mass-spring oscillating sys-tem. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 84

4.20 Standing wave on diaphragm of driver. : : : : : : : : : : : : : 854.21 Standing wave around rim of diaphragm. : : : : : : : : : : : 854.22 Typical frequency response of a cone speaker. : : : : : : : : : 864.23 Ba�e problem in cone driver. : : : : : : : : : : : : : : : : : : 864.24 Front and rear of cone speakers are 180� out of phase. : : : : 874.25 Ba�e action. : : : : : : : : : : : : : : : : : : : : : : : : : : : 884.26 Two possible approaches for trapping rear sound in a speaker

by means of an enclosure. : : : : : : : : : : : : : : : : : : : : 884.27 E�ect of enclosure on frequency response of speaker. : : : : : 894.28 Reducing standing waves inside speaker enclosure. : : : : : : 904.29 Basic bass-re ex enclosure. : : : : : : : : : : : : : : : : : : : 914.30 Oscillating components of bass-re ex speaker. : : : : : : : : : 924.31 Splitting of original resonance into two new resonances in

bass-re ex system. : : : : : : : : : : : : : : : : : : : : : : : : 934.32 Resonant behavior, in-phase and out-of-phase, motion of strongly

coupled components of bass-re ex system. : : : : : : : : : : : 944.33 Coupled components of a bass-re ex speaker. : : : : : : : : : 954.34 Bass-re ex speaker using a passive radiator over the port. : : 964.35 Helmholtz resonator behaves like mass-spring system. : : : : 974.36 Bass-re ex speaker using a port or a duct. : : : : : : : : : : : 984.37 Acoustic labyrinth enclosure. : : : : : : : : : : : : : : : : : : 994.38 Change of frequency response of speaker when a small enclo-

sure is used. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1004.39 E�ect of small enclosure on frequency response of driver. : : : 1014.40 Transfer of energy from a bob to one of equal mass, and to

one of di�erent mass. : : : : : : : : : : : : : : : : : : : : : : : 1024.41 A horn for matching vibrations of a light diaphragm to a large

volume of air. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1034.42 Low frequency response of a horn. : : : : : : : : : : : : : : : 1034.43 Some common horn shapes. : : : : : : : : : : : : : : : : : : : 1044.44 Folded horn. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1054.45 Two-way horn loudspeaker with bass-re ex enclosure. : : : : 1064.46 Standing wave set up in a room with maxima and minima in

sound pressure. : : : : : : : : : : : : : : : : : : : : : : : : : : 107

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4.47 Re ected waves by a wall appear to come from behind thewall since it acts like a mirror. : : : : : : : : : : : : : : : : : 107

4.48 Stereo coverage in a room. : : : : : : : : : : : : : : : : : : : : 1084.49 Speaker phasing: speakers are in phase. : : : : : : : : : : : : 1084.50 Speaker phasing: speakers are out of phase. : : : : : : : : : : 1094.51 Geometry of a Bose 901 speaker. : : : : : : : : : : : : : : : : 1094.52 E�ect of equalizer on frequency response of Bose speakers. : : 1104.53 Bass horn in Klipsch horn speaker. : : : : : : : : : : : : : : : 1114.54 Graphic equalizer. : : : : : : : : : : : : : : : : : : : : : : : : 111

5.1 Example of an atom: a Helium atom. : : : : : : : : : : : : : 1135.2 Forces between charged objects; like charges repel and unlike

charges attract. : : : : : : : : : : : : : : : : : : : : : : : : : : 1145.3 Charged ping-pong balls repelling each other. : : : : : : : : : 1155.4 Electric �eld produced by a charged object. : : : : : : : : : : 1155.5 Electric �eld between two charged plates. : : : : : : : : : : : 1165.6 Examples of voltage sources: a battery, the output of a receiver.1165.7 Electrostatic speaker: basic principle and actual speaker. : : : 1175.8 Simpli�ed version of an electrostatic speaker at equilibrium. : 1175.9 Push-pull action by two plates on charged sheet. : : : : : : : 1185.10 An electrostatic speaker. : : : : : : : : : : : : : : : : : : : : : 1185.11 Some crystals under pressure produce positive and negative

charges on surface. : : : : : : : : : : : : : : : : : : : : : : : : 1195.12 Dimensional changes of a piezoelectric ceramic when a voltage

is applied. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1195.13 Bending action of a double piezoelectric driver. : : : : : : : : 1205.14 Pumping action of cone caused by bending of bimorph. : : : 1205.15 Typical piezo horn. : : : : : : : : : : : : : : : : : : : : : : : : 1215.16 Wire connected between two charged objects allows charges

to be transferred. : : : : : : : : : : : : : : : : : : : : : : : : : 1215.17 Flow of electric current from ampli�er to speaker. : : : : : : : 1225.18 Solid with atoms where electrons are tightly bound and which

does not conduct electricity under normal circumstances. : : 1225.19 Motion of one electron in a conductor in the presence of an

electric �eld. Changes of direction are due to scattering. : : : 1235.20 Temperature dependence of the electrical resistance in a con-

ductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1245.21 Superconductivity at Tc below which the resistance is zero. : 124

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5.22 The resistance to current or to water ow increases as thelength of a conductor or pipe increases. Resistance of 2 isdouble that of 1. : : : : : : : : : : : : : : : : : : : : : : : : : 125

5.23 By increasing the cross-sectional area of a conductor, resis-tance to current or water ow decreases. : : : : : : : : : : : : 125

5.24 Resistor with colored bands to specify its resistance value. : : 1265.25 Pure silicon, silicon doped with arsenic, and silicon doped

with gallium. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1265.26 Example of simple circuit. : : : : : : : : : : : : : : : : : : : : 1265.27 Model using water for electric circuit. : : : : : : : : : : : : : 1275.28 Comparison between DC and AC current. : : : : : : : : : : : 1285.29 Representation of a sound wave by an AC electrical signal. : 1285.30 Variable resistance between X and Y. : : : : : : : : : : : : : 1295.31 Fuse to protect speaker. : : : : : : : : : : : : : : : : : : : : : 1295.32 Two speakers connected in series to one channel of ampli�er. 1295.33 Model of series circuit. : : : : : : : : : : : : : : : : : : : : : : 1305.34 Parallel connection of two speakers to an ampli�er. : : : : : : 1305.35 Model of parallel connections. : : : : : : : : : : : : : : : : : : 1315.36 Parallel connections of hi-� components to house electrical

outlet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1315.37 Response of cone speaker to a force. : : : : : : : : : : : : : : 1325.38 Coil used to produce a magnetic �eld when a current ows

through it. It has inductance. : : : : : : : : : : : : : : : : : : 1335.39 Frequency dependence of impedance associated with induc-

tance. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1345.40 Charging of a capacitor. : : : : : : : : : : : : : : : : : : : : : 1345.41 Charging of a capacitor when polarity of voltage source is

reversed. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1355.42 Frequency dependence of impedance due to capacitance. : : : 1355.43 Inductance in series with woofer prevents high frequencies

from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 1365.44 Capacitance in series with tweeter. It prevents low frequencies

from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 1365.45 Capacitance and inductance in series with mid-range speaker

to prevent the high and low frequencies from reaching it. : : : 1375.46 Impedance curve of driver. : : : : : : : : : : : : : : : : : : : : 137

6.1 Importance of ampli�er in hi-� system. : : : : : : : : : : : : : 1396.2 Basic ampli�er. : : : : : : : : : : : : : : : : : : : : : : : : : : 139

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6.3 Ampli�er command for more current. : : : : : : : : : : : : : 1406.4 Ampli�er command for less current. : : : : : : : : : : : : : : 1406.5 Semiconductor junction. : : : : : : : : : : : : : : : : : : : : : 1416.6 Reverse-biased semiconductor junction. : : : : : : : : : : : : 1416.7 Forward-biased semiconductor junction. : : : : : : : : : : : : 1426.8 Symbol for diodes and its characteristics. : : : : : : : : : : : 1426.9 Recti�er action of a diode when an AC voltage is applied. : : 1426.10 Diagram of transistor and its circuit symbol for two possibilities.1436.11 Ampli�er action of transistor in a circuit compared to control

of water ow. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1436.12 Function of an ampli�er. : : : : : : : : : : : : : : : : : : : : : 1446.13 Ampli�er integrated on a chip. : : : : : : : : : : : : : : : : : 1446.14 Operational ampli�er with negative feedback. : : : : : : : : : 1446.15 Negative feedback corrects uctuations in gain. : : : : : : : : 1456.16 Positive feedback in large hall with a mike and a loudspeaker

system driven by mike. : : : : : : : : : : : : : : : : : : : : : : 1456.17 Volume control. : : : : : : : : : : : : : : : : : : : : : : : : : : 1466.18 Comparison of potentiometer action with energy of a ball on

a ladder. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1466.19 Bass and Treble controls. : : : : : : : : : : : : : : : : : : : : 1476.20 E�ect on signal spectrum of Bass and Treble controls. : : : : 1486.21 Action of LOW and HIGH �lters with 6 dB/octave attenua-

tion, and also with 18 db/octave attenuation. : : : : : : : : : 1486.22 Harmonic distortion by ampli�er. : : : : : : : : : : : : : : : : 1496.23 Non-linear gain of ampli�er. : : : : : : : : : : : : : : : : : : : 1496.24 IM distortion in ampli�er. : : : : : : : : : : : : : : : : : : : : 1506.25 Distortion increases sharply about power rating of ampli�er. : 1506.26 Clipping of waveform by ampli�er at high output levels be-

yond the rated value. : : : : : : : : : : : : : : : : : : : : : : : 1516.27 E�ect of noise from ampli�er. : : : : : : : : : : : : : : : : : : 1516.28 Comparing 2 ampli�ers with the same specs. Even though

their specs are the same, the ampli�ers will sound di�erent. : 1526.29 A-weighted method of measuring noise. : : : : : : : : : : : : 152

7.1 E�ect of current in a wire on compasses around it. : : : : : : 1547.2 Bar magnet has a north pole and a south pole. : : : : : : : : 1547.3 Cutting a bar magnet produces shorter magnets each with its

own respective north and south poles. : : : : : : : : : : : : : 1547.4 Magnetic dipole is the basic unit of magnetism. : : : : : : : : 155

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7.5 Unmagnetized piece of iron. : : : : : : : : : : : : : : : : : : : 1557.6 Alignment of domains in a piece of iron by a bar magnet. Iron

becomes magnetized. : : : : : : : : : : : : : : : : : : : : : : : 1567.7 Magnetic �eld around a bar magnet and a wire carrying a

current. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1567.8 Increasing the magnetic �eld produced by a current in a wire:

by forming a loop, and by using many loops. : : : : : : : : : 1577.9 An electromagnet. : : : : : : : : : : : : : : : : : : : : : : : : 1577.10 Determination of direction of magnetic �eld using �rst left-

hand rule. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1587.11 Rule for determining direction of magnetic �eld in an electro-

magnet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1587.12 First left-hand rule and how a cone speaker works. : : : : : : 1597.13 Force on wire carrying a current in a magnetic �eld. : : : : : 1597.14 The second left-hand rule showing direction of force on wire

carrying a current in a magnetic �eld. : : : : : : : : : : : : : 1607.15 Direction of force depends on orientation of current with re-

spect to magnetic �eld. : : : : : : : : : : : : : : : : : : : : : 1617.16 A Heil Speaker. : : : : : : : : : : : : : : : : : : : : : : : : : : 1627.17 One set of folds in Heil speaker. : : : : : : : : : : : : : : : : : 1637.18 Magnetic Planar Speaker. : : : : : : : : : : : : : : : : : : : : 1647.19 Forces on diaphragm when current direction is as indicated. : 1657.20 A bar magnet moving into a coil induces an electric current

in that coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1657.21 Induced current in coil by moving magnet. : : : : : : : : : : : 1667.22 Signi�cance of relative motion between magnet and coil. : : : 1677.23 Direction of induced current (wrong). : : : : : : : : : : : : : 1677.24 Direction of induced current (correct). : : : : : : : : : : : : : 1687.25 Schematic of a transformer and its circuit symbol. : : : : : : 1697.26 Step-up transformer. : : : : : : : : : : : : : : : : : : : : : : : 1707.27 Step-down transformer. : : : : : : : : : : : : : : : : : : : : : 1707.28 Schematic of microphone based on Faraday's law of induction. 1717.29 Exercise 7.14. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1717.30 Exercise 7.15. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1727.31 Exercise 7.18. : : : : : : : : : : : : : : : : : : : : : : : : : : : 172

8.1 Electric Field around charged ping-pong ball. : : : : : : : : : 1748.2 Oscillating charged ball. : : : : : : : : : : : : : : : : : : : : : 174

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8.3 Generation of electromagnetic waves at two di�erent frequen-cies. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 175

8.4 Spectrum of electromagnetic waves. : : : : : : : : : : : : : : : 1758.5 Electromagnetic waves are transverse waves with oscillating

electric and magnetic �elds. : : : : : : : : : : : : : : : : : : : 1768.6 Production of electromagnetic waves by oscillating electrons

in antenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1768.7 Generation of electric and magnetic �elds by antenna. : : : : 1778.8 Production of electromagnetic waves by antenna. : : : : : : : 1778.9 Some examples of modulation. : : : : : : : : : : : : : : : : : 1788.10 Amplitude modulation. : : : : : : : : : : : : : : : : : : : : : 1788.11 Carrier and audio signals broadcast by two stations. : : : : : 1798.12 Spectrum of an AM carrier at frequency f when modulated

by audio signal. : : : : : : : : : : : : : : : : : : : : : : : : : : 1798.13 Audio frequencies modulating carrier. : : : : : : : : : : : : : 1808.14 Spectrum of frequencies on carrier for audio frequencies up

to 5 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1808.15 Spectrum of frequencies due to modulation of carrier. : : : : 1818.16 Frequency modulation (FM). : : : : : : : : : : : : : : : : : : 1818.17 A low frequency and a high frequency audio signal frequency

modulating a carrier. : : : : : : : : : : : : : : : : : : : : : : : 1828.18 A loud and a quiet audio signal frequency modulating a carrier.1838.19 Action of limiter in FM. : : : : : : : : : : : : : : : : : : : : : 1848.20 Pre-emphasis in FM broadcasting. : : : : : : : : : : : : : : : 1848.21 Information brought to tuner on carrier. : : : : : : : : : : : : 1858.22 De-emphasis of audio information to reduce high frequency

noise. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1858.23 Elements of radio communications. : : : : : : : : : : : : : : : 1868.24 Superheterodyne receiver. : : : : : : : : : : : : : : : : : : : : 1868.25 Processing part of AM signal with a simple diode and �lters. 1868.26 Audio information which will modulate carrier in stereo broad-

casting. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1878.27 Alternating current in antenna produces electromagnetic wave.1888.28 Electric �eld around charged antenna wires is similar to that

between charged capacitor plates. : : : : : : : : : : : : : : : : 1898.29 Magnetic �elds around a wire and antenna with current. : : : 1898.30 Development of a standing wave on antenna. : : : : : : : : : 1908.31 Comparison of standing wave on antenna to that of a string. 191

xi

Page 12: Technical Illustrations

8.32 Radiation pattern of electric �eld around half-wave dipoleantenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 192

8.33 Polar graph representation of radiation pattern around half-wave dipolar antenna. : : : : : : : : : : : : : : : : : : : : : : 192

8.34 Basic elements of a grounded vertical antenna. : : : : : : : : 1938.35 Quarter-wave antenna. : : : : : : : : : : : : : : : : : : : : : : 1938.36 Total antenna length is made shorter by inserting a coil in

series. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1948.37 When the electric �eld of radio wave is vertical, the receiving

antenna should also be vertical. : : : : : : : : : : : : : : : : : 1958.38 Loop antenna detects the magnetic �eld part of radio wave. : 1958.39 Two common loop antennas. : : : : : : : : : : : : : : : : : : 1968.40 Vertically polarized radio wave. : : : : : : : : : : : : : : : : : 1968.41 Horizontally polarized radio wave. : : : : : : : : : : : : : : : 1978.42 Broadcasting with circular polarization. : : : : : : : : : : : : 1978.43 Low frequency ground wave follows curvature of earth. : : : : 1988.44 Direct (line-of-sight) mode of propagation. : : : : : : : : : : : 1988.45 Earth's ionosphere layers. : : : : : : : : : : : : : : : : : : : : 1998.46 Sky wave world communications. : : : : : : : : : : : : : : : : 1998.47 Two-hop transmission of radio wave using ionosphere. : : : : 2008.48 Communication using a satellite. : : : : : : : : : : : : : : : : 2008.49 Selectivity relates to how well alternate channels are rejected. 2018.50 Direct and re ected waves from a broadcasting station. : : : 2018.51 Capture ratio in tuner. : : : : : : : : : : : : : : : : : : : : : : 201

9.1 Record with grooves representing mechanically engraved waves.2039.2 Phono playback systems. : : : : : : : : : : : : : : : : : : : : : 2049.3 Stereo with only one stylus. : : : : : : : : : : : : : : : : : : : 2059.4 A stereo moving magnet phono cartridge. : : : : : : : : : : : 2069.5 Unmagnetized and magnetized magnetic material. : : : : : : 2069.6 Magnetic �eld produced by a coil when current ows through

it. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2079.7 Alignment of domains in a magnetic material. : : : : : : : : : 2089.8 Behavior of magnetic material in a coil whose current is in-

creased and decreased to zero. : : : : : : : : : : : : : : : : : : 2099.9 Memory is destroyed by reversed current in coil. : : : : : : : 2109.10 Hysteresis curve of magnetic material. : : : : : : : : : : : : : 2119.11 Groups of magnetic materials. : : : : : : : : : : : : : : : : : : 2129.12 Side and top views of magnetic tape. : : : : : : : : : : : : : : 213

xii

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9.13 Magnetic particle of gamma { Iron (III) Oxide as used on tapes.2139.14 Recording head aligning magnetic domains on tape. : : : : : 2149.15 Analog recording on a magnetic tape. : : : : : : : : : : : : : 2159.16 Recorded information on magnetic tape. : : : : : : : : : : : : 2169.17 Playback head for reading information on a tape. : : : : : : : 2169.18 Playback head reading signals. : : : : : : : : : : : : : : : : : 2169.19 Order of heads on a tape deck. : : : : : : : : : : : : : : : : : 2179.20 Recording on material with magnetic hysteresis. : : : : : : : 2179.21 Recording a signal on a tape. : : : : : : : : : : : : : : : : : : 2189.22 Ideal magnetic characteristics for tape | linear behavior. : : 2199.23 Useful region on hysteresis curve for magnetic recording. : : : 2209.24 Recording on magnetic tape with bias. : : : : : : : : : : : : : 2219.25 Details of heads for magnetic recording. : : : : : : : : : : : : 2229.26 Frequency dependence of output from playback head. : : : : 2229.27 Output from playback head as a function of frequency for

various gap sizes and tape speeds. : : : : : : : : : : : : : : : 2239.28 Equalization in playback. : : : : : : : : : : : : : : : : : : : : 2239.29 Equalization in recording. : : : : : : : : : : : : : : : : : : : : 2249.30 Typical musical spectrum. : : : : : : : : : : : : : : : : : : : : 2249.31 Frequency response at di�erent recording levels. : : : : : : : : 2259.32 Exercise 9.4. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 225

10.1 Sound wave and its analog representation as a voltage. : : : : 22710.2 Grooves on a record representing analog signals. : : : : : : : 22810.3 Distortion of analog signal by dirt stuck between playback

head and tape. : : : : : : : : : : : : : : : : : : : : : : : : : : 22910.4 Original number 2 and worn out number 2; basic information

is not lost when number is worn out. : : : : : : : : : : : : : : 22910.5 (a) Analog signal, decimal scale (b) Analog signal, binary scale.23010.6 20 Hz wave will get more samples per wave than a 200 Hz wave.23010.7 Aliasing due to inadequate sampling rate. : : : : : : : : : : : 23110.8 Audio spectrum and sideband frequencies due to sampling. : 23210.9 Sample and hold of a signal for digitizing. : : : : : : : : : : : 23310.10 Multiplexing of left and right channels. : : : : : : : : : : : : 23310.11 Digitizing a signal. : : : : : : : : : : : : : : : : : : : : : : : : 23410.12 Output of D-A converter. : : : : : : : : : : : : : : : : : : : : 23410.13 Output of low-pass �lter. : : : : : : : : : : : : : : : : : : : : 23510.14 Main features of playback of digital signal. : : : : : : : : : : 23510.15 Details of information on a CD. : : : : : : : : : : : : : : : : 236

xiii

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10.16 Interference between light beam re ected from pit and from at. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 237

10.17 Focusing action of a laser beam by lens. : : : : : : : : : : : : 23710.18 Reduced e�ect of surface defect on CD. : : : : : : : : : : : : 23810.19 Laser spot focused on disc data. : : : : : : : : : : : : : : : : 23910.20 Three-beam detection; one for read-out and two beams for

tracking. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 24010.21 Randomly polarized beam and plane-polarized beam. : : : : 24110.22 Path of laser beam and role of its polarization. : : : : : : : : 24210.23 Coherent and incoherent beams of light. : : : : : : : : : : : : 24310.24 Semiconductor laser. : : : : : : : : : : : : : : : : : : : : : : : 24410.25 E�ect of 2-times and 4-times oversampling. : : : : : : : : : : 24510.26 Shock-proof memory in mini-disc. : : : : : : : : : : : : : : : 246

11.1 Magnetic digital signals recorded vertically on a mini disc. : : 24811.2 Recording digital signals on a mini disc. : : : : : : : : : : : : 24811.3 Kerr e�ect: plane of polarization of light beam rotates upon

re ection from a magnetized surface. : : : : : : : : : : : : : : 24911.4 Read-out of digital information using Kerr e�ect. Magnetic

�eld direction a�ects plane of polarization of re ected laserbeam. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 249

11.5 Di�erence in read-out between pre-recorded and recordablemini-discs. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 250

11.6 Section of a recordable mini disc. : : : : : : : : : : : : : : : : 25111.7 Layered structure of recordable mini disc. : : : : : : : : : : : 25111.8 Track pattern in DCC tape. : : : : : : : : : : : : : : : : : : : 25211.9 The playback head reads only a portion of the recorded track. 25211.10 Threshold of hearing curve. : : : : : : : : : : : : : : : : : : : 25211.11 Sounds which will be recorded by PASC and masking of quiet

passages. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 25311.12 Representation of digital signal on magnetic tape. : : : : : : 25311.13 Helical recording with rotating heads. : : : : : : : : : : : : : 25411.14 Tape contact to rotating head. : : : : : : : : : : : : : : : : : 25511.15 Time compression to reduce wrap angle. : : : : : : : : : : : 25611.16 Guard band between tracks on analog tape reduces cross-talk.25711.17 Azimuthal recording. : : : : : : : : : : : : : : : : : : : : : : 25711.18 Digital information on magnetic tape recorded longitudinally. 25811.19 Arrangement of signals on a tape. : : : : : : : : : : : : : : : 25911.20 Exercise 11.7. : : : : : : : : : : : : : : : : : : : : : : : : : : 259

xiv

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12.1 Sources of heating in hi-� due to mechanical friction and elec-trical \friction". : : : : : : : : : : : : : : : : : : : : : : : : : : 261

12.2 Electrical \friction" causes heating in ampli�er componentsand voice coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : 262

12.3 Two types of thermometers: alcohol expansion thermometerand gas thermometer. : : : : : : : : : : : : : : : : : : : : : : 263

12.4 Temperature dependence of electric resistance of a semicon-ductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 264

12.5 Basic circuit for resistance thermometer. : : : : : : : : : : : : 26412.6 Heating of spot on mini-disc for recording. : : : : : : : : : : : 26512.7 Heat conduction along a bar between a hot body and a cold

one. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 26512.8 Thermal resistance depends on length of heat conductor. : : : 26612.9 Thermal resistance depends inversely on cross-sectional area

of heat conductor. : : : : : : : : : : : : : : : : : : : : : : : : 26712.10 Transfer of heat in air by convection. : : : : : : : : : : : : : 26812.11 Object at temperature T emits electromagnetic waves. : : : 26812.12 Thermal expansion of an object when heated. : : : : : : : : 26912.13 Bimetallic strip and its behavior when heated or cooled. : : : 26912.14 Mounting of transistor and diode on heat sink to transfer

heat away from devices by heat conduction. : : : : : : : : : : 27012.15 Heat removal by convection and radiation. : : : : : : : : : : 27112.16 Action of circuit-breaker when too hot. : : : : : : : : : : : : 27112.17 Thermo-magnetic recording on mini-Disc. : : : : : : : : : : : 272

13.1 Speed of tape past recording head. : : : : : : : : : : : : : : : 27413.2 Time for a radio wave to go around the Earth at the equator. 27413.3 Speed of a recorded signal is the same at X and at Y; their

velocities are di�erent. : : : : : : : : : : : : : : : : : : : : : : 27513.4 Force on voice coil giving it a push or a pull depending on

direction of current in voice coil. : : : : : : : : : : : : : : : : 27613.5 Force on tape by capstan-pinch roller. : : : : : : : : : : : : : 27713.6 Static friction-force pulling on tape. : : : : : : : : : : : : : : 27713.7 Releasing a CD from its case by applying a pressure on the

clips with a �nger. : : : : : : : : : : : : : : : : : : : : : : : : 27813.8 Inertia of a tweeter is less than that of a woofer. : : : : : : : 27913.9 Outer ear; ear drum's inertia limits response at frequencies

above 20 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : 280

xv

Page 16: Technical Illustrations

13.10 Adjusted weight in cartridge for helping the stylus to trackthe groove in phono record. : : : : : : : : : : : : : : : : : : : 280

13.11 Force of clamped magnet on a voice coil accelerates diaphragmin loudspeaker. Force of clamped magnet on focus coil accel-erates focus lens in CD player. : : : : : : : : : : : : : : : : : 281

13.12 Re ection of a pulse on a string clamped at wall and itsinversion. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 282

13.13 Force on voice coil and force on magnet. : : : : : : : : : : : 28313.14 Waves recorded on a phono record and a CD. : : : : : : : : : 28413.15 Distances covered along outer track and inner track on a

phono record. : : : : : : : : : : : : : : : : : : : : : : : : : : : 28513.16 Frequency of rotation of a CD is made higher near the inner

edge and lower near the outer edge to maintain constant linearspeed on a tracks. : : : : : : : : : : : : : : : : : : : : : : : : 286

13.17 Rotation of drum head relative to magnetic tape in DAT. : : 28613.18 When same force is applied to the CD case lid, it is easier to

open the lid near the edge because torque is larger there. : : 28713.19 For the same force exerted on lid, the torque is larger in B

than in A. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 28813.20 Moment of inertia of a CD is larger than that of a mini-Disc. 288

xvi

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Chapter 1

Introduction to Hi-Fi

1

Page 18: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 2

R

L

Playback Speakers

R

L

Record

Microphone

Microphone

Figure 1.1: Stereo process in recording and playback.

Page 19: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 3

Center Speaker

Stereo Left

Stereo Right

Surround Right

Surround Left

Figure 1.2: Surround sound reproduction of audio information.

Stereo

Left

Right

Store (Record)or

Transmit

Sourcesof

Sound

Left

Right

Stereo

Figure 1.3: Storage or transmission of sound in stereo.

Page 20: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 4

Right

Left

Right

Left

PlaybackSources

ofSound

Figure 1.4: Playback process in stereo.

+

=+

Tuner

Pre-Amplifier

PowerAmplifier

Receiver

Figure 1.5: Elements of a receiver.

Page 21: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 5

Receiver

Antenna

Phono

CD

Tape Deck

DAT

Figure 1.6: Example of basic connections to a receiver.

=+

Pre-Amplifier

PowerAmplifier

Integrated

Amplifier

Figure 1.7: Elements of an integrated ampli�er.

Page 22: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 6

Tuner

CD

Tape Deck

Phono

DAT

Antenna

Integrated Amplifier

Figure 1.8: Connections to an integrated ampli�er.

+

Separate components

Pre-AmpPower

Amplifier

Figure 1.9: All separate approach.

Page 23: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 7

Tuner

CD

Tape Deck

Phono

DAT

Pre-AmpPower

Amplifier

Antenna

Figure 1.10: Connections in all-separate approach.

Page 24: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 8

VCR

AudioInput

AudioOutput

VideoA/V Receiver VCR

L RStereo SpeakerOutput

VideoMonitor

Figure 1.11: Basic A/V System.

Page 25: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 9

VCR

AudioInput

AudioOutput

VideoA/V Receiver VCR

L R

VideoMonitor

Stereo SpeakerOutput

Surround SpeakerOutput

L R

Figure 1.12: A/V receiver driving a surround-sound system.

Page 26: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 10

Out forRecording

In fromTape Deck

SelectorSwitch

Out

In Out

Tape Deck

Tone ControlsTapeMonitorSwitch

Inputs

InOut

Figure 1.13: Details of the tape monitor switch when listening to a soundsource with available tape recording.

Page 27: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 11

Out forRecording

In fromTape Deck

Out

In Out

Tape Deck

Tone ControlsTapeMonitorSwitch

SelectorSwitch

Inputs

In

Out

Figure 1.14: Listening to a tape; tape switch in.

Page 28: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 12

R

A/V Receiver

TV

VCR

Center Channel Speaker

Video Audio

Video

Left SurroundSpeaker

Right SurroundSpeaker

Left Front

Speaker

Right Front

Speaker

Figure 1.15: A/V receiver with Dolby Pro Logic processor.

Page 29: Technical Illustrations

CHAPTER 1. INTRODUCTION TO HI-FI 13

A

Time

B

Time

C

Time

D

Time

E

Time

F

Time

G

Time

Amplitudeof

Signal

Amplitudeof

Signal

Amplitudeof

Signal

Figure 1.16: Various wave forms.

Page 30: Technical Illustrations

Chapter 2

Waves

14

Page 31: Technical Illustrations

CHAPTER 2. WAVES 15

Figure 2.1: Phono record and an enlarged groove showing engraved waverepresenting sound.

Distance

Displacement up

Displacement down

No Waves Waves

EquilibriumPosition

Figure 2.2: Simpli�ed picture of a water wave; displaced water as a functionof position.

Page 32: Technical Illustrations

CHAPTER 2. WAVES 16

Distance

Displacement up

Displacement down

1 Wave

Figure 2.3: Details of one wave as a function of position.

Displacement

Large Amplitude Small Amplitude

Distance

Figure 2.4: Large and small amplitude waves.

Page 33: Technical Illustrations

CHAPTER 2. WAVES 17

Displacementfrom

EquilibriumTime

+

-

Figure 2.5: Time dependence of displacement of a point on a water wave.

Time

+

-1 Period

Displacement

Figure 2.6: Displacement as a function of time; time required to completeone wave.

Page 34: Technical Illustrations

CHAPTER 2. WAVES 18

Clamp Clamp

String

Figure 2.7: Transverse wave on a string.

Figure 2.8: Longitudinal waves along a solid bar.

Position

Wave 1 Wave 2 Result

+ =Position Position

Figure 2.9: Addition of two waves.

Page 35: Technical Illustrations

CHAPTER 2. WAVES 19

No SoundSound

Air

Bell Jar

Vacuum

Figure 2.10: Sound requires a medium in which to propagate; in a vacuumthere is no sound propagation.

Direct Radiator Speaker

Diaphragm

Diaphragm

Drum

Figure 2.11: Direct radiator speaker can move air like a drumhead.

Page 36: Technical Illustrations

CHAPTER 2. WAVES 20

Speaker

Increase in Pressure = Condensation

Motion

SpeakerAir at Atmospheric Pressure

≈ 14.7 lbs./sq.in.

Figure 2.12: Generation of sound by loudspeaker.

Page 37: Technical Illustrations

CHAPTER 2. WAVES 21

Rarefaction Condensation

Equilibrium Pressureat ≈ 14.7 lbs./sq.in.

1 Wave

Pressure Change

Speaker Motion

Motion

Figure 2.13: Disturbances created by loudspeaker; pressure changes causesound.

DistanceEquilibriumAir Pressure

Air PressureIncrease

VibratingSpeaker

Air PressureDecrease

Louder Sound

Figure 2.14: Representation of sound created by a loudspeaker.

Page 38: Technical Illustrations

CHAPTER 2. WAVES 22

Wave XWave Y

Distance Distance

Amplitude Amplitude

0

1

2

-1

-2

0

1

2

-1

-2

Figure 2.15: Wave Y has 4 times the power of wave X, but their amplitudesdi�er only by a factor of 2.

Obstacle

Reflected Wave

Incoming Wave

Normal

Angle of Incidence

Angle of Reflection

Figure 2.16: Re ection of a wave by an obstacle or a di�erent medium.

Page 39: Technical Illustrations

CHAPTER 2. WAVES 23

Sound Produced

Time0

SoundPower

Speaker producesa Pulse of Sound

Figure 2.17: Speaker producing a pulse of sound in a hall.

Page 40: Technical Illustrations

CHAPTER 2. WAVES 24

Sound Produced

Time0

Direct

Reflected

Reflected

Direct

Amountof

Sound

Reverberant Sound

Figure 2.18: Paths of direct and re ected sound in a hall.

Page 41: Technical Illustrations

CHAPTER 2. WAVES 25

Reflected Sound

(Reverberant)

Direct Sound

Figure 2.19: Direct and reverberant sound in a hall.

Page 42: Technical Illustrations

CHAPTER 2. WAVES 26

Amountof

Sound

Source

Direct

Reverberant

About 6 meters from Stage

Distance from Source

Figure 2.20: Direct and reverberant sound contributions to sound in a hall.

Page 43: Technical Illustrations

CHAPTER 2. WAVES 27

1 2 3 4

Figure 2.21: Sound radiated by a speaker; as one moves away the intensitydecreases.

Page 44: Technical Illustrations

CHAPTER 2. WAVES 28

1

2

Figure 2.22: Sound intensity through surface 2 is di�erent from that of 1.

Page 45: Technical Illustrations

CHAPTER 2. WAVES 29

At Rest

Relative Motion

Figure 2.23: Observer and source at rest and in relative motion.

Page 46: Technical Illustrations

CHAPTER 2. WAVES 30

Speaker moving toward Listener

Speaker moving away from Listener

Increase in Frequency heard by Listener

100 Hz Signal

Decrease in Frequency heard by Listener

1000 Hz Signal

Figure 2.24: Doppler E�ect produced by speaker producing simultaneously100 Hz and 1,000 Hz sound waves.

Page 47: Technical Illustrations

CHAPTER 2. WAVES 31

Hot Air

Cold Air

IncomingSoundWave

Figure 2.25: Sound wave in cold air entering hot air.

Hot Air

Cold Air

Normal

Figure 2.26: Refraction of a sound wave.

Page 48: Technical Illustrations

CHAPTER 2. WAVES 32

Hot Air Normal

Cold Air

Critical Angle

Figure 2.27: Above a critical angle of incidence there is only re ection.

Page 49: Technical Illustrations

CHAPTER 2. WAVES 33

Air

Plastic

Sound Waves

Figure 2.28: Sound travels in a curved hollow plastic tube by multiple re- ections.

Page 50: Technical Illustrations

CHAPTER 2. WAVES 34

TimeDisplacement

Figure 2.29: Sound wave produced by a musical group; a complex wave.

Time

Displacement

0

Figure 2.30: Simple sine waveform.

Page 51: Technical Illustrations

CHAPTER 2. WAVES 35

Timeor

Position360˚

360˚

180˚180˚

90˚

90˚

270˚

270˚

Figure 2.31: Comparison between one full wave and one rotation of a circle.

+ =Time

orPosition

Disturbance Disturbance Disturbance

0 0 0Time

orPosition

Timeor

Position

Figure 2.32: Addition of two waves.

+ =Position Position Position

Displacement Displacement Displacement

0 0 0

Figure 2.33: Addition of two waves out of phase by 180 degrees.

Page 52: Technical Illustrations

CHAPTER 2. WAVES 36

In Phase

Figure 2.34: Constructive interference.

Page 53: Technical Illustrations

CHAPTER 2. WAVES 37

Out of Phase

Figure 2.35: Destructive interference.

Page 54: Technical Illustrations

CHAPTER 2. WAVES 38

Figure 2.36: Obstacle with aperture receiving high frequency waves.

Page 55: Technical Illustrations

CHAPTER 2. WAVES 39

Figure 2.37: Low frequency behavior of obstacle and aperture.

Page 56: Technical Illustrations

CHAPTER 2. WAVES 40

Figure 2.38: Comparison of di�raction behavior of a room with opening anda loudspeaker.

Page 57: Technical Illustrations

CHAPTER 2. WAVES 41

Low Frequencies

High Frequencies

Figure 2.39: Dispersion characteristics of a speaker.

Incident Wave

Reflected Wave

Result

Figure 2.40: Standing wave produced by incident and re ected waves.

Page 58: Technical Illustrations

CHAPTER 2. WAVES 42

Figure 2.41: Simplest possible standing wave on a string.

Page 59: Technical Illustrations

CHAPTER 2. WAVES 43

1/2 Wave

Figure 2.42: Simplest standing wave on a string during one cycle.

Node Antinode Node Antinode NodeDisplacement:

Figure 2.43: Second harmonic on a string showing position of nodes andantinodes.

Third Harmonic

Figure 2.44: Third harmonic on a string clamped at both ends.

Page 60: Technical Illustrations

CHAPTER 2. WAVES 44

Or

Figure 2.45: Setting up a standing wave in a tube.

Page 61: Technical Illustrations

CHAPTER 2. WAVES 45

1/2 Wave

DisplacementAntinode

DisplacementAntinode

Node

Figure 2.46: Simplest standing wave in a tube open at both ends.

Second Harmonic

Figure 2.47: Second harmonic in tube open at both ends.

1/2 Wave

1 Meter

Figure 2.48: Fundamental in a tube.

Page 62: Technical Illustrations

CHAPTER 2. WAVES 46

Figure 2.49: Tube open at one end excited by a tuning fork.

1/4 Wave

DisplacementAntinode

DisplacementNode

Figure 2.50: Fundamental in tube open at one end.

Page 63: Technical Illustrations

CHAPTER 2. WAVES 47

3/4 Wave

1/4 Wave 1/4 Wave 1/4 Wave

Figure 2.51: Next more complicated standing wave; the third harmonic.

Fifth Harmonic

Figure 2.52: Fifth harmonic.

1/4 Wave

1 Meter

Figure 2.53: Standing wave in a tube 1 meter long; fundamental.

Page 64: Technical Illustrations

CHAPTER 2. WAVES 48

Figure 2.54: Tube closed at both ends.

1/2 Wave

DisplacementNode

DisplacementNode

Antinode

Figure 2.55: Fundamental of a tube closed at both ends.

Page 65: Technical Illustrations

CHAPTER 2. WAVES 49

z

x

y1/2 Wave

1/2 Wave

1/2 Wave

Figure 2.56: Room where independent standing waves can be set up in thex, y, and z directions.

Page 66: Technical Illustrations

CHAPTER 2. WAVES 50

Figure 2.57: A drumhead �xed at its edges and its fundamental mode ofvibration.

Page 67: Technical Illustrations

CHAPTER 2. WAVES 51

Figure 2.58: Overtone on a drumhead.

Figure 2.59: Standing wave pattern on a Chladni plate.

Page 68: Technical Illustrations

CHAPTER 2. WAVES 52

+ =

100 Hz 400 Hz

Complex Wave

Figure 2.60: Complex wave created by the superposition of a 100 Hz funda-mental and its fourth harmonic.

Page 69: Technical Illustrations

CHAPTER 2. WAVES 53

Figure 2.61: Violin string plucked by a �nger and producing all sorts ofharmonics.

Page 70: Technical Illustrations

CHAPTER 2. WAVES 54

TimeDisplacement

Figure 2.62: Complex wave generated by plucking string.

Page 71: Technical Illustrations

CHAPTER 2. WAVES 55

Amplitude

Time

Frequency Relative Amplitude

3f 1/3

f 1

5f 1/5

nf 1/n

... ...

...

n = odd integer

Figure 2.63: Square wave; it is made up of many harmonics.

Page 72: Technical Illustrations

CHAPTER 2. WAVES 56

RelativeAmplitude

Harmonics

1.0

0.5

0

1 2 3 4 5 6 7

Figure 2.64: Spectrum of a square wave.

Page 73: Technical Illustrations

CHAPTER 2. WAVES 57

Amplitude

Time

Frequency Relative Amplitude

2f 1/2

3f 1/3

f 1

4f 1/4

5f 1/5

nf 1/n

... ... ...

n = integer

Figure 2.65: Sawtooth wave and its harmonic content.

Page 74: Technical Illustrations

CHAPTER 2. WAVES 58

RelativeAmplitude

Harmonics

1.0

0.5

0

1 2 3 4 5 6 7 8

Figure 2.66: Spectrum of a sawtooth wave.

Page 75: Technical Illustrations

CHAPTER 2. WAVES 59

Figure 2.67: A string bowed at its middle and harmonics which are excited.

Page 76: Technical Illustrations

CHAPTER 2. WAVES 60

Hammer

Figure 2.68: String on a piano struck by hammer at a distance 1/10 thestring length from one end.

Frequency

Amplitude

Natural Frequency

Figure 2.69: Vibrations of an object at di�erent excitation frequencies.

Page 77: Technical Illustrations

CHAPTER 2. WAVES 61

Undamped Damped

Oil

Figure 2.70: Oscillations of a mass on a spring, undamped and dampedwhen submersed in oil.

Ping Pong Ball

Figure 2.71: Resonance of wine glass excited by sound.

Page 78: Technical Illustrations

CHAPTER 2. WAVES 62

F1

F2

Time

Time

Time

Resultant

Figure 2.72: Beats caused by the combination of two waves with slightlydi�erent frequencies.

Page 79: Technical Illustrations

Chapter 3

Decibels

63

Page 80: Technical Illustrations

CHAPTER 3. DECIBELS 64

dB

Figure 3.1: Decibel meter.

Volume-70 dB

0 dB

Receiver

Figure 3.2: Receiver with volume control marked in dB.

0

20

40

60

80

100

120

140

20 100 1,000 10,000

Frequency (Hz)

Sou

nd P

ress

ure

Leve

l (dB

)

Range of Human Hearing

Threshold of Hearing

Threshold of Pain

Figure 3.3: Response of human ears at the threshold of hearing.

Page 81: Technical Illustrations

CHAPTER 3. DECIBELS 65

Frequency (Hz)

So

un

d P

ress

ure

Lev

el (

dB

)

20 31.5 63 125 250 500 1000 2000 4000 8000 16000 20000

140

120

100

80

60

40

20

0Threshold of Hearing

10 dB20 dB

30 dB

50 dB

70 dB

90 dB

110 dB

130 dB

40 dB

60 dB

80 dB

100 dB

120 dB

Figure 3.4: Response of human ears for various sound levels: Fletcher-Munson curves.

Outer Ear Tube closed at one End

Figure 3.5: Outer ear approximated by a tube closed at one end.

Page 82: Technical Illustrations

CHAPTER 3. DECIBELS 66

Speaker Sound Level

Meter

(dB Meter)

Aux

Receiver

Audio

Signal

Generator

dB

Figure 3.6: Measuring the frequency response of a speaker.

Sound Level (dB)

Frequency

90

70

20 Hz 1,000 Hz 20,000 Hz

Ideal

Real

Figure 3.7: Frequency response of a speaker.

Page 83: Technical Illustrations

Chapter 4

Loudspeakers

67

Page 84: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 68

ElectricalSignalInput

Loudspeaker

SoundOutput

Figure 4.1: Role of loudspeaker.

Page 85: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 69

Amplitude

FrequencyHarmonics1 2 3 4 5 6 7

Amplitude

Frequency

ResultantAmplitude

FrequencyHarmonics1 2 3 4 5 6 7

Spectrum of an Input Tone

Frequency Response of Speaker

Sound from Speaker

+

Figure 4.2: Distortion of spectrum of original waveform by non- at fre-quency response of speaker.

Page 86: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 70

Low Frequencies

High Frequencies

Figure 4.3: Dispersion properties of speakers.

Page 87: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 71

O1

2

Figure 4.4: Two low frequency waves from speaker arriving at O.

Page 88: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 72

O

1

2

Figure 4.5: Two high frequency waves from speaker arriving at O.

Page 89: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 73

O

1

2

2 1/2 Waves

Figure 4.6: Details of waves 2 and 1 at high frequencies.

Page 90: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 74

Lows

Middles

Highs

"On Axis" All Frequencies

are heard.

"Off Axis" High Frequencies are

almost not heard.

Speaker

Figure 4.7: Sound dispersion of a driver as the frequency is increased.

Page 91: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 75

Woofer

TotalSoundOutput

Midrange

TotalSoundOutput

Tweeter

Frequency

TotalSoundOutput

Cross-over Frequencies

Frequency

Frequency

Figure 4.8: Division of audio spectrum for a three-way loudspeaker.

Page 92: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 76

Woofer Midrange Tweeter

Frequency

TotalSoundOutput

3-Way Speaker

500 Hz 5000 Hz

Figure 4.9: Net e�ect of subdividing the whole audio range into three sec-tions.

Cross-over Frequency

Woofer Tweeter

Frequency

SoundOutput

Figure 4.10: Subdivision of audio spectrum in a two-way system.

Page 93: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 77

Displacement Displacement

A B

Figure 4.11: Amount of sound produced depends on volume displacement.A is louder than B.

Page 94: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 78

Displacement

Displacement

Figure 4.12: To produce same amount of sound by both drivers at the samefrequency, the small one has to move through a larger distance than the bigone.

Page 95: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 79

Frequency0.0005

0.5

500

20 200 2000 20,000

Volume ofAir moved

3(cm )

Figure 4.13: Volume of air moved by loudspeaker as a function of frequencyto produce same loudness of sound.

Page 96: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 80

High Frequency

Low Frequency

Figure 4.14: Low frequency and high frequency simple pendulums doingdi�erent amounts of work per second for same amplitude of displacement.

ElectricalPower

In

SoundPower and

HeatDissipation

IN OUT

Figure 4.15: Balance between electrical power going to driver and the pro-duction of sound power and heat dissipation by driver.

Page 97: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 81

ElectricalPower

Input fromReceiver(80 Watts)

Loudspeaker

SoundOutput

(2 Watts)

Figure 4.16: Example of a loudspeaker whose e�ciency is less than 100%.

Page 98: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 82

Cone

Suspension

Magnet

Voice Coil

Spider

Basket

Figure 4.17: Basic cone speaker.

Page 99: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 83

Cone-shaped Diaphragm Flat Diaphragm

Figure 4.18: Comparison of cone-shape over at shape for mechanicalstrength when thin material is used.

Page 100: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 84

Diaphragm

Flexible Edge

Figure 4.19: Modeling of diaphragm action by mass-spring oscillating sys-tem.

Page 101: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 85

Side View Front View

12

3

1

2

3

Figure 4.20: Standing wave on diaphragm of driver.

Down

Down

Up

Up

Up

Up

Down

Down

N

A

N

A

N

N

A A

N

A

N

A

N

N

A A

N = NodeA = Antinode

Figure 4.21: Standing wave around rim of diaphragm.

Page 102: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 86

SoundPressure

(dB)

Frequency

Main Resonance

Standing Wave Resonances

Figure 4.22: Typical frequency response of a cone speaker.

Front Sound(In Phase)

Rear Sound(Out of Phase)

Rear Sound(Out of Phase)

Figure 4.23: Ba�e problem in cone driver.

Page 103: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 87

Figure 4.24: Front and rear of cone speakers are 180� out of phase.

Page 104: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 88

Baffle

Path = 1/2 Wave

Figure 4.25: Ba�e action.

Figure 4.26: Two possible approaches for trapping rear sound in a speakerby means of an enclosure.

Page 105: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 89

Frequency

Amplitude

With Enclosure

Without Enclosure

Resonant Frequency of Driver

Resonant Frequency of Driver + Enclosure

Frequency

Amplitude

With Enclosure

Without Enclosure

Resonant Frequency of Driver

Resonant Frequency of Driver + Enclosure

OR

Figure 4.27: E�ect of enclosure on frequency response of speaker.

Page 106: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 90

Cotton Wool

Figure 4.28: Reducing standing waves inside speaker enclosure.

Page 107: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 91

Port

Driver

Figure 4.29: Basic bass-re ex enclosure.

Page 108: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 92

Figure 4.30: Oscillating components of bass-re ex speaker.

Page 109: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 93

Frequency

Frequency

Frequency

+

Amplitude

Amplitude

ResultantAmplitude

Driver

Enclosure

Result

Figure 4.31: Splitting of original resonance into two new resonances in bass-re ex system.

Page 110: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 94

DriverAir in Enclosure

Air in Enclosure

Air in Enclosure

Air in Enclosure

Air in Enclosure

Out-of-PhaseMotion

In-PhaseMotion

Figure 4.32: Resonant behavior, in-phase and out-of-phase, motion ofstrongly coupled components of bass-re ex system.

Page 111: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 95

Driver

Airin

EnclosurePort

Figure 4.33: Coupled components of a bass-re ex speaker.

Page 112: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 96

PassiveRadiator

Driver

Figure 4.34: Bass-re ex speaker using a passive radiator over the port.

Page 113: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 97

Spring

Mass

Figure 4.35: Helmholtz resonator behaves like mass-spring system.

Page 114: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 98

Port Duct

Figure 4.36: Bass-re ex speaker using a port or a duct.

Page 115: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 99

Figure 4.37: Acoustic labyrinth enclosure.

Page 116: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 100

Driver + Small Enclosure

Frequency

Amplitude

Driver alone

Very LowResonant Frequency

Figure 4.38: Change of frequency response of speaker when a small enclosureis used.

Page 117: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 101

+Small Enlosure

Frequency

AmplitudeDriver + Small Enclosure

30 Hz

Frequency

Amplitude Driver alone

15 Hz

=

Large Compliance

Figure 4.39: E�ect of small enclosure on frequency response of driver.

Page 118: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 102

Figure 4.40: Transfer of energy from a bob to one of equal mass, and to oneof di�erent mass.

Page 119: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 103

AirChamber

Diaphragm

Throat

Mouth

Figure 4.41: A horn for matching vibrations of a light diaphragm to a largevolume of air.

Frequency

Cut-off Frequency

Amplitude

Figure 4.42: Low frequency response of a horn.

Page 120: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 104

Conical

Exponential

Hyperbolic

Parabolic

Figure 4.43: Some common horn shapes.

Page 121: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 105

Diaphragm

Figure 4.44: Folded horn.

Page 122: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 106

Figure 4.45: Two-way horn loudspeaker with bass-re ex enclosure.

Page 123: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 107

Loudspeaker

1/2 Wavelength

Figure 4.46: Standing wave set up in a room with maxima and minima insound pressure.

LoudspeakerDirect

Figure 4.47: Re ected waves by a wall appear to come from behind the wallsince it acts like a mirror.

Page 124: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 108

Lows

Highs

Middles

Highs

Lows

Middles

Lows

Figure 4.48: Stereo coverage in a room.

L

R

+_

+_ +

_

+_

Figure 4.49: Speaker phasing: speakers are in phase.

Page 125: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 109

L

R

+_

+_

+_

+_

Figure 4.50: Speaker phasing: speakers are out of phase.

Wall

Direct

Reflected Reflected

Figure 4.51: Geometry of a Bose 901 speaker.

Page 126: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 110

Frequency

Amplitude

Speaker

Frequency

Amplitude Equalizer

Frequency

ResultantAmplitude

Speaker

Figure 4.52: E�ect of equalizer on frequency response of Bose speakers.

Page 127: Technical Illustrations

CHAPTER 4. LOUDSPEAKERS 111

Wall

Figure 4.53: Bass horn in Klipsch horn speaker.

+12 dB

0 dB

-12 dB62Hz 250Hz 1kHz 4kHz 8kHz

Left Channel

Figure 4.54: Graphic equalizer.

Page 128: Technical Illustrations

Chapter 5

Electricity

112

Page 129: Technical Illustrations

CHAPTER 5. ELECTRICITY 113

N

N

Neutron

Proton

Electron

Electron

Figure 5.1: Example of an atom: a Helium atom.

Page 130: Technical Illustrations

CHAPTER 5. ELECTRICITY 114

Figure 5.2: Forces between charged objects; like charges repel and unlikecharges attract.

Page 131: Technical Illustrations

CHAPTER 5. ELECTRICITY 115

Figure 5.3: Charged ping-pong balls repelling each other.

Figure 5.4: Electric �eld produced by a charged object.

Page 132: Technical Illustrations

CHAPTER 5. ELECTRICITY 116

Figure 5.5: Electric �eld between two charged plates.

Output

Receiver

Left Right

Battery

Figure 5.6: Examples of voltage sources: a battery, the output of a receiver.

Page 133: Technical Illustrations

CHAPTER 5. ELECTRICITY 117

Plates

Sheet

Figure 5.7: Electrostatic speaker: basic principle and actual speaker.

Sheet

Plates

Figure 5.8: Simpli�ed version of an electrostatic speaker at equilibrium.

Page 134: Technical Illustrations

CHAPTER 5. ELECTRICITY 118

Figure 5.9: Push-pull action by two plates on charged sheet.

Plates

Diaphragm (Vibrating Sheet)

Spacers

Figure 5.10: An electrostatic speaker.

Page 135: Technical Illustrations

CHAPTER 5. ELECTRICITY 119

Si Ion

O Ion

Stress

Stress

2

Quartz

Figure 5.11: Some crystals under pressure produce positive and negativecharges on surface.

V V

V = 0

Figure 5.12: Dimensional changes of a piezoelectric ceramic when a voltageis applied.

Page 136: Technical Illustrations

CHAPTER 5. ELECTRICITY 120

V

V

Figure 5.13: Bending action of a double piezoelectric driver.

Bimorph

Cone

Figure 5.14: Pumping action of cone caused by bending of bimorph.

Page 137: Technical Illustrations

CHAPTER 5. ELECTRICITY 121

Diaphragm

Figure 5.15: Typical piezo horn.

Wire

Figure 5.16: Wire connected between two charged objects allows charges tobe transferred.

Page 138: Technical Illustrations

CHAPTER 5. ELECTRICITY 122

L

R

+_

+_

Figure 5.17: Flow of electric current from ampli�er to speaker.

Bound Electrons

Atom

Figure 5.18: Solid with atoms where electrons are tightly bound and whichdoes not conduct electricity under normal circumstances.

Page 139: Technical Illustrations

CHAPTER 5. ELECTRICITY 123

Electron

Figure 5.19: Motion of one electron in a conductor in the presence of anelectric �eld. Changes of direction are due to scattering.

Page 140: Technical Illustrations

CHAPTER 5. ELECTRICITY 124

ElectricalResistance

Temperature (˚K)0 100 200 300

Metal

Figure 5.20: Temperature dependence of the electrical resistance in a con-ductor.

ElectricalResistance

Temperature (˚K)0 100 200 300

Tc

Superconductor

Figure 5.21: Superconductivity at Tcbelow which the resistance is zero.

Page 141: Technical Illustrations

CHAPTER 5. ELECTRICITY 125

Water flowing in Pipe

Wire of Conductor

1

2

1

2

Figure 5.22: The resistance to current or to water ow increases as thelength of a conductor or pipe increases. Resistance of 2 is double that of 1.

Wire of Conductor Water flowing in Pipe

Figure 5.23: By increasing the cross-sectional area of a conductor, resistanceto current or water ow decreases.

Page 142: Technical Illustrations

CHAPTER 5. ELECTRICITY 126

Figure 5.24: Resistor with colored bands to specify its resistance value.

SiSi Si

Si Si

SiSi Si

Ga

SiSi Si

Si Si

SiSi Si

As

Extra Electron

Missing ElectronBonding

SiSi Si

SiSi Si

SiSi Si

= Hole

Figure 5.25: Pure silicon, silicon doped with arsenic, and silicon doped withgallium.

+

_

Amplifier VoltageSource

Simple Model

Resistance

Figure 5.26: Example of simple circuit.

Page 143: Technical Illustrations

CHAPTER 5. ELECTRICITY 127

Water Flow

Pump Resistance toWater Flow

Figure 5.27: Model using water for electric circuit.

Page 144: Technical Illustrations

CHAPTER 5. ELECTRICITY 128

Current

Time

DC

Current

Time

AC

Figure 5.28: Comparison between DC and AC current.

Time

Pressure Sound

Time

Voltage AC Signal

Figure 5.29: Representation of a sound wave by an AC electrical signal.

Page 145: Technical Illustrations

CHAPTER 5. ELECTRICITY 129

X Z

Y

Figure 5.30: Variable resistance between X and Y.

VoltageSource

Fuse

Fine Wire

Figure 5.31: Fuse to protect speaker.

L

R

+_

+_

Speaker 1 Speaker 2

Figure 5.32: Two speakers connected in series to one channel of ampli�er.

Page 146: Technical Illustrations

CHAPTER 5. ELECTRICITY 130

VoltageSource

Effective Resistor

Speaker 1 Speaker 2

Figure 5.33: Model of series circuit.

L

R

+_

+_

Figure 5.34: Parallel connection of two speakers to an ampli�er.

Page 147: Technical Illustrations

CHAPTER 5. ELECTRICITY 131

VoltageSource

Effective Resistor

Speaker 1

Speaker 2

Figure 5.35: Model of parallel connections.

HouseOutlet

120 V60 Hz

CDPlayer

Receiver Etc.Equalizer

Figure 5.36: Parallel connections of hi-� components to house electricaloutlet.

Page 148: Technical Illustrations

CHAPTER 5. ELECTRICITY 132

Mass

Suspension

• Compliance of Suspension

• Friction

• Mass of Cone

Figure 5.37: Response of cone speaker to a force.

Page 149: Technical Illustrations

CHAPTER 5. ELECTRICITY 133

Figure 5.38: Coil used to produce a magnetic �eld when a current owsthrough it. It has inductance.

Page 150: Technical Illustrations

CHAPTER 5. ELECTRICITY 134

20 Hz 20,000 HzFrequency

Impedancedue to

Inductance

Figure 5.39: Frequency dependence of impedance associated with induc-tance.

VoltageSource

VoltageSource

Figure 5.40: Charging of a capacitor.

Page 151: Technical Illustrations

CHAPTER 5. ELECTRICITY 135

VoltageSource

VoltageSource

Figure 5.41: Charging of a capacitor when polarity of voltage source isreversed.

20 Hz 20,000 HzFrequency

Impedancedue to

Capacitance

Figure 5.42: Frequency dependence of impedance due to capacitance.

Page 152: Technical Illustrations

CHAPTER 5. ELECTRICITY 136

Frequency

SoundOutput

Woofer

Inductance

In fromAmplifier

Woofer

Figure 5.43: Inductance in series with woofer prevents high frequencies fromreaching it.

Frequency

SoundOutput

Capacitance

In fromAmplifier

Tweeter

Tweeter

Figure 5.44: Capacitance in series with tweeter. It prevents low frequenciesfrom reaching it.

Page 153: Technical Illustrations

CHAPTER 5. ELECTRICITY 137

Frequency

SoundOutput

In fromAmplifier

Mid-range

Mid-range

Figure 5.45: Capacitance and inductance in series with mid-range speakerto prevent the high and low frequencies from reaching it.

Resonant FrequencyFrequency

Impedance

Figure 5.46: Impedance curve of driver.

Page 154: Technical Illustrations

Chapter 6

Ampli�ers

138

Page 155: Technical Illustrations

CHAPTER 6. AMPLIFIERS 139

WeakSignals

LargeSignals

AmplifierSources of

Audio Signals(CD, Tape, etc.)

Figure 6.1: Importance of ampli�er in hi-� system.

Source Commandfrom Audio Signals

SoundOutput

PowerSupply

Figure 6.2: Basic ampli�er.

Page 156: Technical Illustrations

CHAPTER 6. AMPLIFIERS 140

Source Command:

SoundOutput

More Current

PowerSupply

Figure 6.3: Ampli�er command for more current.

Source Command:

SoundOutput

Less Current

PowerSupply

Figure 6.4: Ampli�er command for less current.

Page 157: Technical Illustrations

CHAPTER 6. AMPLIFIERS 141

p-Type n-Type

Holes Electrons

Figure 6.5: Semiconductor junction.

No Current flow

BatteryBattery

p-type n-type p-type n-type

Figure 6.6: Reverse-biased semiconductor junction.

Page 158: Technical Illustrations

CHAPTER 6. AMPLIFIERS 142

Battery Battery

Current flows

p-type n-type p-type n-type

Figure 6.7: Forward-biased semiconductor junction.

Current

+Voltage-Voltage

Figure 6.8: Symbol for diodes and its characteristics.

Voltageacross

Resistor

InputVoltage

Diode

Figure 6.9: Recti�er action of a diode when an AC voltage is applied.

Page 159: Technical Illustrations

CHAPTER 6. AMPLIFIERS 143

n p n p n p

Emitter EmitterCollector Collector

BaseBase

Figure 6.10: Diagram of transistor and its circuit symbol for two possibilities.

Commandgoes in as

Current

(Control)PowerSupply

Current Flow

Water Flow

Control

Water Tank

Figure 6.11: Ampli�er action of transistor in a circuit compared to controlof water ow.

Page 160: Technical Illustrations

CHAPTER 6. AMPLIFIERS 144

Amplifier

Signal In

Signal Out

Figure 6.12: Function of an ampli�er.

Input

OutputAmplifier

+ Battery

- Battery

Inverting

Non-InvertingInput

Ground

Figure 6.13: Ampli�er integrated on a chip.

Input

OutputAmplifier

Rf

Rinput

Figure 6.14: Operational ampli�er with negative feedback.

Page 161: Technical Illustrations

CHAPTER 6. AMPLIFIERS 145

Input

OutputAmplifier

Rf

Rinput

Figure 6.15: Negative feedback corrects uctuations in gain.

Amplifier

Microphone

Speaker

Figure 6.16: Positive feedback in large hall with a mike and a loudspeakersystem driven by mike.

Page 162: Technical Illustrations

CHAPTER 6. AMPLIFIERS 146

Input

Output

Ground

Figure 6.17: Volume control.

Input

Output isMaximum Voltage

Ground

Ball atMaximum

Energydue to itsPosition

Input

Output isMinimum Voltage

Ground

Ball atMinimum Energy

due to itsPosition

Figure 6.18: Comparison of potentiometer action with energy of a ball on aladder.

Page 163: Technical Illustrations

CHAPTER 6. AMPLIFIERS 147

Bass Treble

Min Max Min Max

Figure 6.19: Bass and Treble controls.

Page 164: Technical Illustrations

CHAPTER 6. AMPLIFIERS 148

RelativeOutput

(dB)

+ 13

-13

Frequency

Min. Bass

Max. bass

Min. Treble

Max. Treble

1000 Hz20 Hz 20,000 Hz

MiddlePosition

Figure 6.20: E�ect on signal spectrum of Bass and Treble controls.

RelativeAmplitude

(dB)

Frequency20 Hz 20,000 Hz

Low, 6 dB/Octave

Low, 18 dB/Octave

High, 6 dB/Octave

High, 18 dB/Octave

Ideal Casewith no Filter

Figure 6.21: Action of LOW and HIGH �lters with 6 dB/octave attenuation,and also with 18 db/octave attenuation.

Page 165: Technical Illustrations

CHAPTER 6. AMPLIFIERS 149

Amplifier

Signal In

Signal Out

Extra Harmonics

f

Signal Outf

2f 3f

+ + + ... =

Figure 6.22: Harmonic distortion by ampli�er.

Linear

Non-linear

Output

Input

Figure 6.23: Non-linear gain of ampli�er.

Page 166: Technical Illustrations

CHAPTER 6. AMPLIFIERS 150

Signal In

Frequency f 1

Frequency f 2Amplifier

Signal Out

f 1

f 2

f 1 f 2-

f 1 f 2+

Figure 6.24: IM distortion in ampli�er.

Distortion(%)

Power Output

IM

THD

Power Rating of Amplifier

Figure 6.25: Distortion increases sharply about power rating of ampli�er.

Page 167: Technical Illustrations

CHAPTER 6. AMPLIFIERS 151

Signal In

Amplifier

Signal Out

Large THDdue to Clipping

Figure 6.26: Clipping of waveform by ampli�er at high output levels beyondthe rated value.

Signal In

Amplifier

Signal Out

Noise

Figure 6.27: E�ect of noise from ampli�er.

Page 168: Technical Illustrations

CHAPTER 6. AMPLIFIERS 152

RelativeOutput

(dB)

20 Hz 20,000 Hz

A

Frequency

RelativeOutput

(dB)

20 Hz 20,000 Hz

B

Frequency

Figure 6.28: Comparing 2 ampli�ers with the same specs. Even though theirspecs are the same, the ampli�ers will sound di�erent.

20 Hz 20,000 HzFrequency

0 dB Noise Level

A - weighted Measured Noise Level

Figure 6.29: A-weighted method of measuring noise.

Page 169: Technical Illustrations

Chapter 7

Electromagnetism

153

Page 170: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 154

Current

Figure 7.1: E�ect of current in a wire on compasses around it.

North South

Figure 7.2: Bar magnet has a north pole and a south pole.

North South N S N S

Figure 7.3: Cutting a bar magnet produces shorter magnets each with itsown respective north and south poles.

Page 171: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 155

N SN S

Current

Magnetic Field Magnetic Field

Figure 7.4: Magnetic dipole is the basic unit of magnetism.

Magnetic DomainIron Atom

Figure 7.5: Unmagnetized piece of iron.

Page 172: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 156

N S

Magnet

Magnetized Iron

North South

Figure 7.6: Alignment of domains in a piece of iron by a bar magnet. Ironbecomes magnetized.

North South

Current

Figure 7.7: Magnetic �eld around a bar magnet and a wire carrying a cur-rent.

Page 173: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 157

Single LoopMany Loops = Coil

Battery

Figure 7.8: Increasing the magnetic �eld produced by a current in a wire:by forming a loop, and by using many loops.

S

Power Supply

N

- +

Figure 7.9: An electromagnet.

Page 174: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 158

S

Power Supply

N

- +

Figure 7.10: Determination of direction of magnetic �eld using �rst left-handrule.

North Pole

Current

S N

- +

Left Hand

Figure 7.11: Rule for determining direction of magnetic �eld in an electro-magnet.

Page 175: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 159

Amplifier

Fixed Magnet

N SN S

Direction of Motion

Figure 7.12: First left-hand rule and how a cone speaker works.

Current

Force

N S

Figure 7.13: Force on wire carrying a current in a magnetic �eld.

Page 176: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 160

Force

Current(Negative to Positive)

Magnetic Field(North to South)

Left Hand

Figure 7.14: The second left-hand rule showing direction of force on wirecarrying a current in a magnetic �eld.

Page 177: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 161

Current

Zero Force

Magnetic Field

Current

Maximum Force

Magnetic Field

Figure 7.15: Direction of force depends on orientation of current with respectto magnetic �eld.

Page 178: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 162

SSS

+

Magnet Poles

Magnet Poles

N NN

Figure 7.16: A Heil Speaker.

Page 179: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 163

SMagnet Pole

NMagnet Pole

Force Force

Wire with Current

Figure 7.17: One set of folds in Heil speaker.

Page 180: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 164

NS SN

SN NS

+

Magnet

Wire

Sheet

N S

Figure 7.18: Magnetic Planar Speaker.

Page 181: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 165

NS S N

NS S N

Wire

Figure 7.19: Forces on diaphragm when current direction is as indicated.

N S

Figure 7.20: A bar magnet moving into a coil induces an electric current inthat coil.

Page 182: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 166

N S

N S

N SN S

Figure 7.21: Induced current in coil by moving magnet.

Page 183: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 167

N S

N S

Figure 7.22: Signi�cance of relative motion between magnet and coil.

N S

WRONG!!

Figure 7.23: Direction of induced current (wrong).

Page 184: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 168

N S

CORRECT!!

Figure 7.24: Direction of induced current (correct).

Page 185: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 169

Secondary CoilPrimary Coil

Core

Figure 7.25: Schematic of a transformer and its circuit symbol.

Page 186: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 170

Secondary CoilPrimary Coil

Figure 7.26: Step-up transformer.

Secondary CoilPrimary Coil

Figure 7.27: Step-down transformer.

Page 187: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 171

N S

Figure 7.28: Schematic of microphone based on Faraday's law of induction.

S N

Figure 7.29: Exercise 7.14.

Page 188: Technical Illustrations

CHAPTER 7. ELECTROMAGNETISM 172

NS

Stationary

+

Figure 7.30: Exercise 7.15.

SN

Figure 7.31: Exercise 7.18.

Page 189: Technical Illustrations

Chapter 8

Electromagnetic Waves and

Tuners

173

Page 190: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 174

Figure 8.1: Electric Field around charged ping-pong ball.

Figure 8.2: Oscillating charged ball.

Page 191: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 175

Oscillating Charged CombHigh-frequency

Oscillating Electron

Figure 8.3: Generation of electromagnetic waves at two di�erent frequencies.

Radio Microwave Infrared Light Ultra-violet X-rays Gamma-rays

10 Hz6 10 Hz8 10 Hz12 10 Hz14 10 Hz15 10 Hz16 10 Hz18

Figure 8.4: Spectrum of electromagnetic waves.

Page 192: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 176

Electric Field

Magnetic Field

Direction of Travel

Figure 8.5: Electromagnetic waves are transverse waves with oscillating elec-tric and magnetic �elds.

Antenna

e-

e-

Waveform

VoltageSource

Antenna

e-

e-

Waveform

VoltageSource

Figure 8.6: Production of electromagnetic waves by oscillating electrons inantenna.

Page 193: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 177

MagneticField

ElectricField

Figure 8.7: Generation of electric and magnetic �elds by antenna.

Broadcasted Wave

Antenna

Figure 8.8: Production of electromagnetic waves by antenna.

Page 194: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 178

Test

Pressure Increase

Pressure Decrease

AmbientPressure

Writing

Painting a Picture Sound

Modulation:

Figure 8.9: Some examples of modulation.

Carrier

AudioSignal

Amplitude ModulatedCarrier Wave

Figure 8.10: Amplitude modulation.

Page 195: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 179

AudioSignal

AudioSignal

Station 1,000 kHz

ModulatedCarrier Wave

Station 1,400 kHz

Carrier

Carrier

ModulatedCarrier Wave

Figure 8.11: Carrier and audio signals broadcast by two stations.

Frequency

Amplitude

f - AudioFrequency

f + AudioFrequency

f

Carrier

Figure 8.12: Spectrum of an AM carrier at frequency f when modulated byaudio signal.

Page 196: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 180

Frequency

Amplitude

f

Carrier

AM Waves

Figure 8.13: Audio frequencies modulating carrier.

Frequency

RelativeAmplitude

ff - 5 kHz f + 5 kHz

Sideband Frequencies

Carrier

Figure 8.14: Spectrum of frequencies on carrier for audio frequencies up to5 kHz.

Page 197: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 181

Frequency

RelativeAmplitude

1000 kHz995 kHz 1005 kHz

1 Station Next Station

Carrier 1 Carrier 2

Figure 8.15: Spectrum of frequencies due to modulation of carrier.

AudioSignal

CarrierSignal

Frequency Modulated Carrier Wave

Amplitude does not change

Frequency changes

Figure 8.16: Frequency modulation (FM).

Page 198: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 182

Low Frequency Audio

Carrier

High Frequency Audio

Carrier

Figure 8.17: A low frequency and a high frequency audio signal frequencymodulating a carrier.

Page 199: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 183

Quiet Audio

Carrier

Loud Audio

Carrier

Figure 8.18: A loud and a quiet audio signal frequency modulating a carrier.

Page 200: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 184

Spikes

Limiter

Figure 8.19: Action of limiter in FM.

RelativeAmplitude

(dB)

0

17

20 Hz 1 kHz 15 kHz

Audio Information

Frequency

Figure 8.20: Pre-emphasis in FM broadcasting.

Page 201: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 185

Relative Amplitude

(dB)

0

17

20 Hz 1 kHz 15 kHz

Audio Information

Frequency

Noise picked upin Atmosphere

Figure 8.21: Information brought to tuner on carrier.

RelativeAmplitude

(dB)

-17

0

20 Hz 1 kHz 15 kHz

Audio Information

Frequency

Noise

Figure 8.22: De-emphasis of audio information to reduce high frequencynoise.

Page 202: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 186

Tuner

Antenna

Amp

OutIn

Transmitter

Antenna

Figure 8.23: Elements of radio communications.

rfAmplifier Out

LocalOscillator

MixerIF

Amplifier

Rectifierand

Filter

Figure 8.24: Superheterodyne receiver.

Rectifier

I-F Signal A-F Signal

Filter

Figure 8.25: Processing part of AM signal with a simple diode and �lters.

Page 203: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 187

Frequency

Amplitude

50 15,000 19,000 23,000 38,000 53,000 Hz

Pilot Frequency

L+R L-R L-R

Figure 8.26: Audio information which will modulate carrier in stereo broad-casting.

Page 204: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 188

Electric Field

Antenna

At the same time ...

Magnetic Field

Figure 8.27: Alternating current in antenna produces electromagnetic wave.

Page 205: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 189

Antenna WiresCapacitor Plates

Electric Field Electric Field

Figure 8.28: Electric �eld around charged antenna wires is similar to thatbetween charged capacitor plates.

Current

Wire with Current

Antenna with Current

Magnetic Field

Current

Current

Figure 8.29: Magnetic �elds around a wire and antenna with current.

Page 206: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 190

Incident Current Wave

Reflected Current Wave

Resultant WaveCurrent

Figure 8.30: Development of a standing wave on antenna.

Page 207: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 191

Standing Wave on an Antenna

Standing Wave on a String

Current

Displacement

Figure 8.31: Comparison of standing wave on antenna to that of a string.

Page 208: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 192

Antenna Axis

Figure 8.32: Radiation pattern of electric �eld around half-wave dipole an-tenna.

Antenna

270˚

180˚

90˚

Radiation Lobe

Figure 8.33: Polar graph representation of radiation pattern around half-wave dipolar antenna.

Page 209: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 193

Current

Antenna

Co-axial Cable

to Electronics

1/4 Wave

Earth

1/4 Wave

Earth

Reflection

Electric Conductor

1/4 Wave

Figure 8.34: Basic elements of a grounded vertical antenna.

1/4 Wave

Ground Plane

Figure 8.35: Quarter-wave antenna.

Page 210: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 194

Reflected Part

Earth

Figure 8.36: Total antenna length is made shorter by inserting a coil inseries.

Page 211: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 195

Electric Field of Radio Wave Receiving

Antenna

Figure 8.37: When the electric �eld of radio wave is vertical, the receivingantenna should also be vertical.

Magnetic Field of Radio Wave

Tuner

Loop Antenna

Figure 8.38: Loop antenna detects the magnetic �eld part of radio wave.

Page 212: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 196

Magnetic Core

(Ferrite)

Loop Antennawith many turns

Loop Antennawith many turnsand Ferrite Core

Figure 8.39: Two common loop antennas.

Electric Field

BroadcastAntenna

Earth ReceivingAntenna

Vertical Polarization

Figure 8.40: Vertically polarized radio wave.

Page 213: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 197

Electric Field

BroadcastAntenna

ReceivingAntenna

Earth

Horizontal Polarization

Figure 8.41: Horizontally polarized radio wave.

2 Mutually Perpendicular

Antennas

Circularly Polarized Wave

Figure 8.42: Broadcasting with circular polarization.

Page 214: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 198

BroadcastAntenna Ground Wave

Earth

Figure 8.43: Low frequency ground wave follows curvature of earth.

BroadcastAntenna Straight Line

Path

Earth

Figure 8.44: Direct (line-of-sight) mode of propagation.

Page 215: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 199

Earth

300 Miles

D

F1

F2

30 Miles

70 miles

50 Miles

150 Miles

Ionosphere

Figure 8.45: Earth's ionosphere layers.

BroadcastAntenna

Reflected Sky

Wave

Ionosphere

Earth

Figure 8.46: Sky wave world communications.

Page 216: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 200

BroadcastAntenna

Ionosphere

Earth

Figure 8.47: Two-hop transmission of radio wave using ionosphere.

Earth

Geostationary Satellite

Figure 8.48: Communication using a satellite.

Page 217: Technical Illustrations

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 201

Dial on Tuner

99.6 100

100.2

100.4

99.8

MHz

Figure 8.49: Selectivity relates to how well alternate channels are rejected.

BroadcastAntenna Receiver

Direct

Reflected

Figure 8.50: Direct and re ected waves from a broadcasting station.

Receiver

100 Mhz

100 Mhz

Should be suppressed

Figure 8.51: Capture ratio in tuner.

Page 218: Technical Illustrations

Chapter 9

Analog Recording and

Playback

202

Page 219: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 203

Top View

Side View

LeftChannel

RightChannel

Figure 9.1: Record with grooves representing mechanically engraved waves.

Page 220: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 204

Output

Piezoelectric Element

MagnetS

Piezoelectric Pick-up

Moving Magnet Pick-up

N

Figure 9.2: Phono playback systems.

Page 221: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 205

90˚

Left

Right

Figure 9.3: Stereo with only one stylus.

Page 222: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 206

S N

Figure 9.4: A stereo moving magnet phono cartridge.

Unmagnetized Magnetic MaterialMagnetization is Zero

Magnetized Magnetic MaterialMagnetization is Non-Zero

Magnetic Domain

Figure 9.5: Unmagnetized and magnetized magnetic material.

Page 223: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 207

Current

Current in Coil

Magnetic Field in Coil

Magnetic Field

Figure 9.6: Magnetic �eld produced by a coil when current ows through it.

Page 224: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 208

Current in Coil

TotalMagnetization

Saturation

Figure 9.7: Alignment of domains in a magnetic material.

Page 225: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 209

Current in Coil

TotalMagnetization

Rententivity

Saturation

Figure 9.8: Behavior of magnetic material in a coil whose current is increasedand decreased to zero.

Page 226: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 210

Current in Coil

Magnetization

CoercivityCurrent in Coil

Figure 9.9: Memory is destroyed by reversed current in coil.

Page 227: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 211

Magnetic Field of Coil

Magnetization

Magnetic Field of Coil

Magnetization

Figure 9.10: Hysteresis curve of magnetic material.

Page 228: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 212

Soft

Hard

Figure 9.11: Groups of magnetic materials.

Page 229: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 213

1L 1

1R 2

2L 3

2R 4

Magnetic Particles

Polyester Film

Heads

Side View

Top View

Stereo

Figure 9.12: Side and top views of magnetic tape.

Figure 9.13: Magnetic particle of gamma { Iron (III) Oxide as used on tapes.

Page 230: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 214

AudioInput

Tape Motion

N S

S N N S

Figure 9.14: Recording head aligning magnetic domains on tape.

Page 231: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 215

1 Wave

Domain AlignmentS N

Domain Alignment

SN

Audio Signal:

Top Viewof Tape

1 Wave

Audio Signal:

Top Viewof Tape

Figure 9.15: Analog recording on a magnetic tape.

Page 232: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 216

N S NS N S NS

1 Wave 1 Wave

High Frequency Low Frequency

Figure 9.16: Recorded information on magnetic tape.

Tape Motion

Output

Gap (Exaggerated)

NS N S

Figure 9.17: Playback head for reading information on a tape.

Tape Motion

Output

1 Wave

NS N S

Figure 9.18: Playback head reading signals.

Page 233: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 217

Erase Record Playback

Tape

Figure 9.19: Order of heads on a tape deck.

Magnetization

Magnetization

Recording Currentin Coil

Recording Currentin Coil

Figure 9.20: Recording on material with magnetic hysteresis.

Page 234: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 218

Magnetization

Recording Currentin Coil

Input Currentto Coil

RecordedInformation

Figure 9.21: Recording a signal on a tape.

Page 235: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 219

Magnetization

Current in Input Coil

Recorded Information

InputInformation

Linear Characteristic of Tape

Figure 9.22: Ideal magnetic characteristics for tape | linear behavior.

Page 236: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 220

Magnetization

Currentin Coil

Region to be avoided

Almost Linear Regions

Figure 9.23: Useful region on hysteresis curve for magnetic recording.

Page 237: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 221

0

+

Audio + Bias on Tape

Audio + Bias Input

Audio Output

Audio InputA-C Bias Input

Figure 9.24: Recording on magnetic tape with bias.

Page 238: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 222

Erase Record Playback

BiasOscillator

Recording Amplifier

AudioSignal

PlaybackAmplifier

Figure 9.25: Details of heads for magnetic recording.

Frequency

Output fromPlayback Head

20,000 Hz20 Hz

Figure 9.26: Frequency dependence of output from playback head.

Page 239: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 223

Frequency

Output fromPlayback Head

20 kHz20 Hz 10 kHz

4 m Gap

Frequency

Output fromPlayback Head

20 kHz20 Hz 10 kHz

17/8 i.p.s.

71/2 i.p.s.

15 i.p.s.

µ

2 m Gapµ

1 m Gapµ

Figure 9.27: Output from playback head as a function of frequency forvarious gap sizes and tape speeds.

Frequency

Output(dB)

20 kHz20 Hz 10 kHz1000 Hz100 Hz

120 sec Equalizationµ

70 sec Equalizationµ

Figure 9.28: Equalization in playback.

Page 240: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 224

Frequency

Output(dB)

20 kHz20 Hz 5000 Hz

Figure 9.29: Equalization in recording.

Time

Amplitude

Average Sound Levels

Transients

Figure 9.30: Typical musical spectrum.

Page 241: Technical Illustrations

CHAPTER 9. ANALOG RECORDING AND PLAYBACK 225

Frequency

RecordingLevel(dB)

20 kHz10 Hz 10 kHz

0

-10

-20

1 kHz

Figure 9.31: Frequency response at di�erent recording levels.

X Y

Figure 9.32: Exercise 9.4.

Page 242: Technical Illustrations

Chapter 10

Digital Optical Recording &

Playback

226

Page 243: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 227

Time

Pressure

Time

Voltage

ContinuousRepresentation

Figure 10.1: Sound wave and its analog representation as a voltage.

Page 244: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 228

Groove

Scratch

Very Large Amplitude Signal

High Frequency Signal

Figure 10.2: Grooves on a record representing analog signals.

Page 245: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 229

Playback

Tape MotionDirt

Played Back SignalRecorded Signal

Tape

Figure 10.3: Distortion of analog signal by dirt stuck between playback headand tape.

2Original Number 2 Worn out Number 2

Figure 10.4: Original number 2 and worn out number 2; basic informationis not lost when number is worn out.

Page 246: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 230

Amplitude(Decimal)

Time0

8

42

Amplitude(Binary)

Time000000100100

1000

Figure 10.5: (a) Analog signal, decimal scale (b) Analog signal, binary scale.

Time

20 Hz

200 HzTime

Figure 10.6: 20 Hz wave will get more samples per wave than a 200 Hz wave.

Page 247: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 231

Samples (not enough!)

SignalAliased Signal

Samples (good!)

Signal

No Aliasing

Figure 10.7: Aliasing due to inadequate sampling rate.

Page 248: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 232

Frequency

Signal

Sampling Frequency

FS F + F / 2SS

Frequency

Alias Zone

FS F + F / 2SSF > F / 2S

Poor, Aliasing, Maximum Signal Frequency F > F / 2S

Good, No Aliasing, Maximum Signal Frequency F = F / 2S

F = F / 2S

Figure 10.8: Audio spectrum and sideband frequencies due to sampling.

Page 249: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 233

Sampling Points

Amplitude

Time

Holds

Sample and Hold of Analog Signal

Figure 10.9: Sample and hold of a signal for digitizing.

Right

Left

MultiplexerOut

In

In

2 Channels 1 Channel

Figure 10.10: Multiplexing of left and right channels.

Page 250: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 234

Analog Signal Sampled Analog Signal Digital Signal

Sample&

Hold

Low-PassFilter

Left Channel

A/DConverter

Sample&

Hold

Low-PassFilter

Right Channel

A/DConverter

FirstMultiplexer

1000 011101100100 0101

00110011

0010 0010

00010001

Figure 10.11: Digitizing a signal.

Output from D/A Converter

Figure 10.12: Output of D-A converter.

Page 251: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 235

Output from D/A Converter

Smoothing byLow-pass

Filter

Figure 10.13: Output of low-pass �lter.

D/A Converter Low-PassFilter

Left ChannelIn

Left ChannelAnalog Out

Digital

0100100011011001

Figure 10.14: Main features of playback of digital signal.

Page 252: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 236

Disc Travels Slower

Disc Travels Faster

Pits and Lands

To keep constant Laser Beam to Disc Speed

Figure 10.15: Details of information on a CD.

Page 253: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 237

Pit 1/4 Wave

Out of Phase by 1/2 Wave

Land

Laser Beam

Figure 10.16: Interference between light beam re ected from pit and from at.

PitsLabel

Compact Disc

Protective Layer

Metal Film Layer

Transparent Substrate

Lens

In

Out

Laser Beam

Figure 10.17: Focusing action of a laser beam by lens.

Page 254: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 238

Compact Disc

Lens

Laser Beam

Dirt

Dirt out of Focus

Figure 10.18: Reduced e�ect of surface defect on CD.

Page 255: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 239

Pit Length

Land Length

Pit Land

0.8 mµLaser Beam

0.5 mµTrack Width

1.6 mµTrack Pitch

Figure 10.19: Laser spot focused on disc data.

Page 256: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 240

Laser Beam to Track

Laser Beamto Read

DiscDirection

Laser Beam to Track

Pit

Figure 10.20: Three-beam detection; one for read-out and two beams fortracking.

Page 257: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 241

Plane PolarizedRandomly Polarized

WaveWave

Figure 10.21: Randomly polarized beam and plane-polarized beam.

Page 258: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 242

Horizontally Polarized Light

Cylindrical LensConverging Lens

Beam Splitter

Objective Lens

Compact Disc

To Detector

1/4 Wave Plate

Vertically Polarized

Light

Out

In from Laser

CircularlyPolarized

Light

Figure 10.22: Path of laser beam and role of its polarization.

Page 259: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 243

Coherent Beam of Light

Incoherent Beam of Light

Figure 10.23: Coherent and incoherent beams of light.

Page 260: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 244

Current

Rear Mirror

Current

pn Junction

Front Mirror

Laser Beam

Figure 10.24: Semiconductor laser.

Page 261: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 245

4 Oversampled×

Sampled Signal

2 Oversampled×

Figure 10.25: E�ect of 2-times and 4-times oversampling.

Page 262: Technical Illustrations

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 246

Mini Disc

Optical Readout

In: 1.4 MBit / Second

Out: 0.3 MBit / Second

Memory

Figure 10.26: Shock-proof memory in mini-disc.

Page 263: Technical Illustrations

Chapter 11

Digital Magnetic Recording

& Playback

247

Page 264: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK248

Track

Magnetic Domains

Figure 11.1: Magnetic digital signals recorded vertically on a mini disc.

RecordingMagnetic Head

Mini Disc

Protective Layer

Substrate

Lens

Laser Beam

Magnetic Recording

Layer

Signal In

Figure 11.2: Recording digital signals on a mini disc.

Page 265: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK249

N

S

Rotation of Polarization Plane

Reflected

Laser BeamIn

Polarization

Magnet

Figure 11.3: Kerr e�ect: plane of polarization of light beam rotates uponre ection from a magnetized surface.

Lens Lens

Polarization Plane

In Out

Record Head

Record Head

Figure 11.4: Read-out of digital information using Kerr e�ect. Magnetic�eld direction a�ects plane of polarization of re ected laser beam.

Page 266: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK250

Change in Intensity

Lens Lens

In Out

Recordable Disc

Change in Polarization Plane

Kerr Effect

Lens Lens

In Out

Bright Less Bright

Prerecorded Disc

InterferenceEffect

Recordable Disc

Figure 11.5: Di�erence in read-out between pre-recorded and recordablemini-discs.

Page 267: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK251

Magneto-optic Layer

Reflective Layer

SiN

SiN

Pre-groove

Pre-grooved for Tracking

Laser Spot

Figure 11.6: Section of a recordable mini disc.

Program AreaLead-in Area

Lead-out Area

Figure 11.7: Layered structure of recordable mini disc.

Page 268: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK252

Lower Sector

Upper Sector

Figure 11.8: Track pattern in DCC tape.

Upper Sector

Left

Right

Record Read

DCC Head

Analog Playback

Only

012345678

012345678

Record Playback

Digital

Figure 11.9: The playback head reads only a portion of the recorded track.

.02 .05 .1 .2 .5 1 2 5 10 20 kHz

SPL-dB

Treshold of Hearing

Frequency

Figure 11.10: Threshold of hearing curve.

Page 269: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK253

.02 .05 .1 .2 .5 1 2 5 10 20 kHz

SPL-dB

New Treshold

Record

Ignore

Frequency

Figure 11.11: Sounds which will be recorded by PASC and masking of quietpassages.

Tape

1 1

0

Audio Signal:

Figure 11.12: Representation of digital signal on magnetic tape.

Page 270: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK254

Slanted Tape Path

Tape

Audio Tracks

Head Drum

Record / Play Head

Figure 11.13: Helical recording with rotating heads.

Page 271: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK255

90˚

Record / Play Head B

Record / Play Head A

Tape

Figure 11.14: Tape contact to rotating head.

Page 272: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK256

Head B

90˚Wrap Angle

Head A

One Revolution

Signal

Signal

Head A

Head B

1/4 Revolution

Figure 11.15: Time compression to reduce wrap angle.

Page 273: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK257

Side A

Side B

Guard Band

Left

Left

Right

Right

Analog Cassette Track Pattern

Figure 11.16: Guard band between tracks on analog tape reduces cross-talk.

Tape

Head B

Guard Band not necessary

Head A

Figure 11.17: Azimuthal recording.

Page 274: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK258

Tape

+ 20˚ Azimuth

- 20˚ Azimuth

B A

Figure 11.18: Digital information on magnetic tape recorded longitudinally.

Page 275: Technical Illustrations

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK259

Tape

Audio

AB

Subcode ATF

SubcodeATF

Figure 11.19: Arrangement of signals on a tape.

XY

+

Figure 11.20: Exercise 11.7.

Page 276: Technical Illustrations

Chapter 12

Heat

260

Page 277: Technical Illustrations

CHAPTER 12. HEAT 261

Friction causes Heating

Mechanical Friction

Electrical "Resistance" due to Collisions of Electrons and Vibrating Ions

Moving Electrons

Vibrating Ions+

++

+

+

+

Metallic Wire

Stylus

Friction causes Heating

Groove

Motion Friction causes Heating

Friction causes Heating

Figure 12.1: Sources of heating in hi-� due to mechanical friction and elec-trical \friction".

Page 278: Technical Illustrations

CHAPTER 12. HEAT 262

Current

Heat

Voice Coil

Speaker

DiodeCurrent

ResistorCurrent

HeatHeat

Heat

Current

Transistor

Figure 12.2: Electrical \friction" causes heating in ampli�er componentsand voice coil.

Page 279: Technical Illustrations

CHAPTER 12. HEAT 263

Alcohol

0 °C

100 °C

Pressure

Gas

Figure 12.3: Two types of thermometers: alcohol expansion thermometerand gas thermometer.

Page 280: Technical Illustrations

CHAPTER 12. HEAT 264

-50 °CTemperature

ElectricalResistancein arbitrary

units

0 °C 50 °C 100 °C

Cold Hot

Figure 12.4: Temperature dependence of electric resistance of a semiconduc-tor.

Resistance Thermometer Element

CurrentMeter

Battery

Figure 12.5: Basic circuit for resistance thermometer.

Page 281: Technical Illustrations

CHAPTER 12. HEAT 265

TbFeCo

Aluminum

Laser Beam

Section of Mini-Disc Section of Mini-DiscT above CurieTemperature

T at Room Temperature

≈ 1000 Å

To Record

Figure 12.6: Heating of spot on mini-disc for recording.

Hot Cold

Heat Flow

LargeAmplitude

SmallAmplitude

Figure 12.7: Heat conduction along a bar between a hot body and a coldone.

Page 282: Technical Illustrations

CHAPTER 12. HEAT 266

Hot Cold

Hot Cold

Heat

Heat

Smaller Thermal

Resistance

Larger Thermal

Resistance

Figure 12.8: Thermal resistance depends on length of heat conductor.

Page 283: Technical Illustrations

CHAPTER 12. HEAT 267

Hot Cold

Heat

Smaller Thermal

Resistance

Larger Thermal

ResistanceHot Cold

Heat

Cross-sectional Area

Figure 12.9: Thermal resistance depends inversely on cross-sectional area ofheat conductor.

Page 284: Technical Illustrations

CHAPTER 12. HEAT 268

Source of Heat

Cold Air

Warm Air

Figure 12.10: Transfer of heat in air by convection.

Object Temperature = T

+ +Vibrating Charges

ElectromagneticWave

Figure 12.11: Object at temperature T emits electromagnetic waves.

Page 285: Technical Illustrations

CHAPTER 12. HEAT 269

Vibrationof Atoms

Vibrationof Atoms

At some Temperature

When Temperature has Increased

Figure 12.12: Thermal expansion of an object when heated.

Brass

Steel Cool

Hot

Flame Ice

Figure 12.13: Bimetallic strip and its behavior when heated or cooled.

Page 286: Technical Illustrations

CHAPTER 12. HEAT 270

Transistor

Unmounted Diode

Heat Sink withLarge Area

Heat Sink withLarge Area

Mounted

Figure 12.14: Mounting of transistor and diode on heat sink to transferheat away from devices by heat conduction.

Page 287: Technical Illustrations

CHAPTER 12. HEAT 271

Holes

Hot Air Radiation

Cold Air Holes

Convection

Figure 12.15: Heat removal by convection and radiation.

Too Hot

Open Circuit

Current In

Current Out

Reset ButtonMaterials with different

Expansion Amounts

Figure 12.16: Action of circuit-breaker when too hot.

Page 288: Technical Illustrations

CHAPTER 12. HEAT 272

Write Head

Spot Heated above Curie Temperature

Magnetic Film

Write Head

Spot Cools in Field of Write Head

Motion

Heat to Record Recorded

Laser Off

Signal InSignal In

Figure 12.17: Thermo-magnetic recording on mini-Disc.

Page 289: Technical Illustrations

Chapter 13

Mechanics

273

Page 290: Technical Illustrations

CHAPTER 13. MECHANICS 274

Recording Head

Direction of TravelDistance travelled in

Elapsed Time

Tape

Figure 13.1: Speed of tape past recording head.

Earth

Figure 13.2: Time for a radio wave to go around the Earth at the equator.

Page 291: Technical Illustrations

CHAPTER 13. MECHANICS 275

Rotation

Velocity is 0.4 m/sec, left

Velocity is 0.4 m/sec, down

Phono Record

X

Y

Figure 13.3: Speed of a recorded signal is the same at X and at Y; theirvelocities are di�erent.

Page 292: Technical Illustrations

CHAPTER 13. MECHANICS 276

+

+

Fixed Magnet

NSForce

Fixed Magnet

NSForce

Figure 13.4: Force on voice coil giving it a push or a pull depending ondirection of current in voice coil.

Page 293: Technical Illustrations

CHAPTER 13. MECHANICS 277

Capstan

Tape

Pinch-Roller

Tape Direction

Force

Figure 13.5: Force on tape by capstan-pinch roller.

Capstan

Tape

Pinch-Roller

Tape Direction

Force of Static Friction

No Motion between Tape and Pinch-Roller and Capstan

Figure 13.6: Static friction-force pulling on tape.

Page 294: Technical Illustrations

CHAPTER 13. MECHANICS 278

Clips

CD

Figure 13.7: Releasing a CD from its case by applying a pressure on theclips with a �nger.

Page 295: Technical Illustrations

CHAPTER 13. MECHANICS 279

Woofer has Large Inertia

Tweeter has Small Inertia

Figure 13.8: Inertia of a tweeter is less than that of a woofer.

Page 296: Technical Illustrations

CHAPTER 13. MECHANICS 280

Outer Ear

Eardrum

Sound

Figure 13.9: Outer ear; ear drum's inertia limits response at frequenciesabove 20 kHz.

Stylus

CartridgeTone Arm

Weight of Cartridge for Tracking Groove in

Phono Record

Figure 13.10: Adjusted weight in cartridge for helping the stylus to trackthe groove in phono record.

Page 297: Technical Illustrations

CHAPTER 13. MECHANICS 281

Information Tracks on CD

Fixed Magnet

Current(Audio)

N S

Speaker Mechanism

Focus Coil

Moving Coil to Focus

Laser Beam for CD

Lens

S SN N

Figure 13.11: Force of clampedmagnet on a voice coil accelerates diaphragmin loudspeaker. Force of clamped magnet on focus coil accelerates focus lensin CD player.

Page 298: Technical Illustrations

CHAPTER 13. MECHANICS 282

Wall

Pulse on String Pulls on Wall

Wall

Wall Pulls on String causing

Pulse

Figure 13.12: Re ection of a pulse on a string clamped at wall and itsinversion.

Page 299: Technical Illustrations

CHAPTER 13. MECHANICS 283

Bar Magnet

Current

N S

Force on Voice Coil

Force on Bar Magnet

Because of this, Magnet must be clamped

Figure 13.13: Force on voice coil and force on magnet.

Page 300: Technical Illustrations

CHAPTER 13. MECHANICS 284

Phono Record

Both at same Frequency

Constant Frequency of Rotation

CD

Both at same FrequencyVariable Frequency of Rotation

Figure 13.14: Waves recorded on a phono record and a CD.

Page 301: Technical Illustrations

CHAPTER 13. MECHANICS 285

Phono Record

Circumference at

Circumference at

router

r inner

r inner

router

2 routerπ

2 r innerπ

Figure 13.15: Distances covered along outer track and inner track on aphono record.

Page 302: Technical Illustrations

CHAPTER 13. MECHANICS 286

CD

Rotation Rate at 200 rpm

Rotation Rate increased to 500 rpm

Figure 13.16: Frequency of rotation of a CD is made higher near the inneredge and lower near the outer edge to maintain constant linear speed on atracks.

Record / Play Heads

Tape Guide

Tape

2000 rpm

Drum

Figure 13.17: Rotation of drum head relative to magnetic tape in DAT.

Page 303: Technical Illustrations

CHAPTER 13. MECHANICS 287

A. Harder to Open

CD

CD Case Lid

B. Easier to Open

CD

CD Case Lid

Figure 13.18: When same force is applied to the CD case lid, it is easier toopen the lid near the edge because torque is larger there.

Page 304: Technical Illustrations

CHAPTER 13. MECHANICS 288

A

DistanceLid

Hinge Point

B

Distance

Lid

Hinge Point

Force

Force

Small TorqueLarge Torque

Figure 13.19: For the same force exerted on lid, the torque is larger in Bthan in A.

CD

MD

Figure 13.20: Moment of inertia of a CD is larger than that of a mini-Disc.