EXHIBIT 2010
`
`EXHIBIT 20 1 O
`
`

`
`THX Ltd. Exhibit 2010 Page 1
`IPR2014-00235
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`THX Ltd. Exhibit 2010 Page 1
`IPR2014-00235
`
`

`
`THX Ltd. Exhibit 2010 Page 2
`IPR2014-00235
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`THX Ltd. Exhibit 2010 Page 2
`IPR2014-00235
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`

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`THX Ltd. Exhibit 2010 Page 3
`IPR2014-00235
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`THX Ltd. Exhibit 2010 Page 3
`IPR2014-00235
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`

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`l2Z
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`ACOUSTICAL ENGINEERING
`
`absorbing material. Longitudinal isolation of the walls of the duct shou-kl
`be provided to prevent longitudinal transmission of sound by the walls 01'.
`the duct. This can be accomplished by the use of rubber connectors zit’
`regular intervals. The walls of the duct should be rigid so that air—b0rnie'
`sounds are not
`transmitted through the walls. Very high attenuatioii , _
`can be obtained in ducts of this type.
`'
`.
`The attenuation, in decibels per foot, in a square or rectangular conduit"-.,
`lined with absorbing material may be obtained from the following empirical:
`formula,“
`
`,
`
`.|.'
`__
`
`;
`
`ACOUSTICAL ELEM:
`
`'
`
`'
`
`ELECTRICAL cmculr
`
`VM5i~iEs
`Qt
`
`'
`
`5.113 ,. '.
`
`ii? : 12.6(x1'4 5'
`ft
`A
`where P = perimeter, in inches,
`A = cross-sectional area in square inches, and
`a — absorption coefficient of the material used for lining the duct.
`Equation 5.113 holds for square ducts and rectangular ducts in which -
`the ratio between the two sides is not greater than two.
`-
`The general subject47v48 of tubes lined with absorbing material, with ’
`both rigid and vibratile walls, has been considered theoretically and experi
`mentally.
`5.38. Response of a Vibrating System of One Degree of Freedom.—
`Consider the electrical circuit, consisting of inductance, electrical resistance,
`and electrical capacitance and a voltage connected in series, as shown in .
`Fig. 5.20. The resonant frequency, in cycles per second, is given by
`
`I I:
`
`RESPONSE
`
`i
`
`.
`
`.
`
`.
`
`:
`
`.
`
`"'
`
`.
`
`‘L-.fr
`
`500
`. \\
`L '
`"2 "3 "4 "5 "6 "7"B"9 2°
`
`5.114-i -
`
`'
`
`_
`
`" .
`‘
`.
`5
`
`'
`
`FIG. 5.20. The current response c iaracteristics of a simple series
`circuit as a function of the ratio f + f,, where f, = the resonant
`frequency, and f = the frequency under consideration. The
`numbers of the characteristics refer to the value of Q,, Q, :
`2nf,L/75. The above characteristics are applicable to acoustical
`and mechanical systems by the substitution of the elements and
`quantities which are analogous to the electrical system.
`
`1
`
`jwcfi.
`
`)
`
`5.11
`
`'
`
`_'
`
`-'1 ',
`'
`
`The curient response characteristics as function of the ratio f + fr for
`
`_
`
`various values of Q, are shown in Fig. 5.20.
`- The above characteristics are applicable to acoustical and mechanical
`' systems by the substitution of the elements and quantities which are analo-
`~_ gous to the electrical system (see Chapter IV).
`3'.
`
`1
`27-: \/LCE
`
`fr 2
`.
`.
`,
`Where L = Inductance: In henrles: and
`CE = electrical Capacitance, in fal-ads_
`_
`_
`’
`_
`_
`The Current m the Clrcult 13 gwcn by
`1':
`
`8
`
`n.~ +¢(wL +
`where 73 = electrical resistance, in ohms,
`e = driving voltage, in volts, and
`1' = current, in amperes.
`The quantity Q, is given by
`
`Q»
`
`w,L
`75'
`
`where w, = Zn-f,.
`45 Sabine, H. J., jour, Auous. Soc. Amzr., Vol. 12, N0. 1, p. 53, 1940.
`47 Sivian, L. ]., jam’. Anous. Soc. Amen, Vol. 9, N0. 2, p. 135, 1937.
`43 M0lloy_ C. T_, _/0'L£1_ Acous. Soc. Amer, Vol. 16, No. 1, p. 31, 194-4.
`
`THX Ltd. Exhibit 2010 Page 4
`IPR2014-00235
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`

`
`6
`
`DIRECT RADIATOR LOUDS PEAKE RS
`
`is an electroacoustic transducer
`6.1. Intr0duction.1 A loudspeaker
`designed to radiate acoustical energy into a room or open air. There
`are two general types of loudspeakers in use today, namely:
`the direct
`radiator and the horn type loudspeaker. The diaphragm of the direct
`radiator loudspeaker is coupled directly to the air. The diaphragm of the
`horn loudspeaker is coupled to the air by means of a horn. The direct
`radiator loudspeaker will be considered in this chapter and the horn loud-
`speaker will be considered in the following chapter.
`The almost universal use of the direct radiator loudspeaker is due to
`the simplicity of construction, small space requirements, and the relatively
`uniform response characteristic. Uniform response over a moderate fre-I
`quency band may be obtained with any simple, direct radiator dynamic
`loudspeaker. However,
`reproduction over a wide frequency range is
`restricted by practical limitations. The two extreme ends of the audio-
`frequency band are the most difficult to reproduce with efliciency comparable
`to that of the midnaudiovfrequency range.
`Inefficiency at the low frequencies
`is primarily due to the small radiation mechanical resistance. There are a
`number of means available for increasing the radiation mechanical resistance
`at the low frequencies. A large radiation mechanical resistance may be
`' obtained by using a large cone. A phase inverter consisting of a completely
`enclosed cabinet with ports provides a means for extending the low~frequency
`range. A horn may be used for presenting a large radiation mechanical
`resistance to a diaphragm at the low frequencies. The efficiency of a direct
`radiator loudspeaker at the high frequencies is limited by the mechanical
`mass reactance of the vibrating system. There are a number of arrange-
`ments suitable for reducing the mass of the vibrating system at the high
`frequencies. Two or more separate loudspeaker mechanisms may be used,
`each designed to reproduce a certain portion of the range. Multiple cones
`driven by a single voice coil may be arranged so that the mass of the system
`decreases at the high frequencies. The voice coil may be sectionalized to
`decrease the mass and inductance at the high frequencies and thereby
`increase the high-frequency range. Multiple coils and multiple cones
`1 Mawardi, Osman K., jowr. Acnus. Soc. Amer, Vol. 26, No. 1, p. 1, 1954.
`
`DIRECT RADIATOR LOUDSPEAKERS
`
`I25
`
`combined into a single mechanism may be designed to yield uniform response
`to the upper limit of audibility.
`.
`_
`.
`It is the purpose of this chapter to outline the factors which influence
`the performance of the conventional, direct radiator loudspeaker, to illustrate
`systems for controlling the response with respect to frequency and to describe
`several means for decreasing the effective mass of the vibrating systems at the
`high frequencies and for improving the efficiency at the low frequencies.
`6.2. Single-Coil, Single-Cone Loudspeakei‘.—The sirpqle ilytpamic
`loudspeaker consists of a paper cone’ driven by a voice coi
`oca e
`H1 3
`magnetic field. A cross—sectional view,
`the voice coil_ circuit and the
`mechanical circuit of a dynamic loudspeaker are shown in Fig. 6.1. The
`
`m C
`
`CV5 FMS
`
`mA
`
`IMA
`
`FIELD
`STRUCTURE
`_/
`
`_
`
`CROSS-SECTIONAL
`VIEW
`
`¢ou_
`
`ELECTRICAL CIRCUIT
`
`MECHANICAL
`or
`THE
`MECHANICAL
`
`CIRCUIT
`
`SYSTEM
`
`FIG. 6.1. Cross—sectional view of a single—coil, Single-CODE. dire“ T§diat°F»
`d namic loudspeaker mechanism mounted in a baffle.
`In the V0166: 0011
`-
`—
`i:
`‘
`.
`.
`q
`.
`_
`V
`d
`_
`.
`iicuit oi
`the internal voltave of the generator. mm = the internal electrical
`resistance of the generator. up and L —‘ the electricallresistagics ind
`Sale
`tance of the voice coil.
`:51»: = the m0t10“a1 electflca lffpeca °_'the COm_
`mechanical circiiit, 7410 = the mass of the cone and voice coi .
`.i_1s -
`_
`-
`=
`‘h
`'
`pliance of the suspension system.
`has = the mechamcal Teslstance of mi
`suspension system._
`7544 = the mass of the air lo:-:1: {ma mt1t1}'ieII::*3O'~iC:‘::1l‘)33
`resistance of the air load.
`fa, 2 the meChaI10m0 Vev OTC?
`_
`‘
`3,“; = the mechanical impedance due to the electrical circuit.
`f)10 = the
`meclianomotive force of the mechanical generator.
`
`total mechanical impedance in mechanical ohms, of the vibrating system
`at the voice coil is
`
`7
`.
`.
`ZMT : 7’MS ‘i’ 7’MA ‘l'.7‘”W‘C +]wmA _ LUCMS
`
`where rMS = mechanical resistance of the suspension system, in mefihanlcal
`ohms,
`
`1/MA = mechanical resistance of the air load, in mechanical Ohms,
`m0 = mass of the cone and the voice coil, in grams,
`mA = mass of the air load, in grams. and
`CMS .: compliance of the suspension system, in centimeters per dyne.
`
`THX Ltd. Exhibit 2010 Page 5
`IPR2014-00235
`
`

`
`l26
`
`ACOUSTICAL ENGINE:
`
`Equation 6.1 may be written as follows
`
`ZMT = 7’MS -.- VMA -i-jxivrc + _7-xll/IA *7'%Ms
`where rM,g mechanical resistance of the suspension system, in in
`ohms,
`731,1 : mechanical resistance of the air load, in mechanical 0
`25310 : wmc = mechanical reactance of the voice coil and co
`mechanical ohms,
`
`-.
`
`xMA = oumA = mechanical reactance of the air load,
`ohms, and
`1
`= mechanical reactance of the suspension sys
`wCMs
`mechanical ohms.
`
`xM5 =
`
`in me'_"
`
`The mechanical resistance and mechanical reactance of the air lo
`be obtained from Sec. 5.10 and Fig. 5.2.
`'
`The motional electrical impedance? in abohms, of the mechanical
`is
`
`23.4 =
`I
`
`(B02
`ZMT
`
`where B = flux density in air gap, in gausses,
`Z = length of the conductor in the voice coil, in centimeter
`21.” 2 total mechanical
`impedance of
`the mechanical
`sysu
`mechanical ohms.
`'
`
`The efficiency of the loudspeaker is the ratio of the sound powe
`to the electrical power input. The efficiency, in per cent, may be‘E'_;
`from the voice coil circuit of Fig. 6.1 and expressed as follows,
`'
`7.83
`= —————--~
`1'50 + VEM X
`
`100
`
`H
`
`where 753
`
`component of the motional electrical resistance due,-
`radiation of sound, in abohms,
`rEM = total motional electrical resistance, in abohms, and
`750 = damped electrical resistance of the voice coil, in abohn'i_
`
`L.‘-
`127
`Iig DIRECT RADIATOR LOUDSPEAKERS
`ifyiihe-discussion assume that the mechanical reactance and
`eisiétaiice of the suspension svstem are zero. The mechanical
`characteristics of the mechanical system’ are shown in Fig. 6.2.
`lsfgmall, compared to xMA and xMc, equation 6.3 becomes
`
`x 100
`
`(Bl)27'_rL[A
`_
`M — rEc(xMA + «‘¢Mc)2
`
`
`“STE” %DIAMETER INCHES | ‘
`
`ss or CONE GRAMS mi-.'1_
`MASS or VOICE coxL.c-RAMS
`to Lima: susezusuon BIND’
`MECH. RES.
`5usi5ENsIoN
`2°°
`voi
`COIL MATERWA
`AIR GAP rcux GAL-ssts
`ioooo
`
`Ioooa
`
`6.6
`
`-IMPEDANCE
`MECHANICAL
`
`EFFICIENCV
`
`IMPEDANCE
`MECHANICAL
`
`C?»
`
`EFFIOENCY
`
`The components 733 and r1,-M may be obtained from equations
`6.3.
`
`'
`
`,RCWENCY
`
`FREQUENCY
`
`'
`
`I
`'
`F REQUENCY
`
`From equations 6.2, 6.3, and 6.4, the efficiency, in per cent, of the
`speaker is
`
`2
`
`(B1)2”MA
`(31) 2(7’MS + 7’MA) + 1’Ec[(1’Mc + 7MA)2 + (xMA + xMC —xMs) 2]
`
`X .1
`4
`
`'u
`
`2Olson, “Dynamical Analogies,” D. Van Nostrand Company, Princetol
`1943.
`'-5
`
`ifha mechanical impedance rec uencv c aaracteristics of three direct radiator
`gr’: having 1-inch, 4-inch, and 16-inch diameter cones.
`x_-,,g = the mechanical
`e-dire" to the cone and coil.
`xMS : the mechanical reactance due to the suspen-
`'1-‘[55 x,“ = the mechanical
`reactance due to the air
`load.
`11:” = the
`a "resistance due to the air load. The efficiency characteristics shown are for
`wits as shown in the table and the graphs of the mechanical impedances.
`In
`en_cy characteristics,
`ii; = the etficiency for his equal *0 Z31’0-
`#2 = the
`ey,ior :1“ as indicated by the graph.
`
`THX Ltd. Exhibit 2010 Page 6
`IPR2014-00235
`
`

`
`l2 8
`
`ACOUSTICAL ENGINEERING
`
`DIRECT RADlATOR.LOUDSPEAKERS
`
`o
`
`.IN'nEcn3EL$Ni
`
`‘Lossda
`EFFICIE-NC.‘-’
`
`The efficiency loss in a direct radiator loudspeaker as 8-
`I ' Fig 6 3
`.1”; where m1 —= the mass of the voice
`{motion of the ratio
`mo + mi’
`.
`-31 m1, = the mass of the diaphragm, "74 = the ‘T1353 0f the 3”
`‘s.
`‘ cad
`The maximum efficiency is arbitrarily depicted as 0 db.
`
`s3a4 it is not practical to make the
`_ al, in commercial loudspeaker
`As a matter of fact‘, the cone mass
`equal to the voice-coil mass.
`A consideration of equation
`v several times the voice-C011 mass‘
`d by the use of a llght-Welght
`that the efficiency can be increase
`
`9 a
`
`n
`
`‘
`
`
`
`OUTPUTINDB 0:
`
`ow
`
`25
`2.0
`l,5
`RELATIVE com-: MASS
`
`FIG. 6.4-. Output of a. typical direct radiator
`loudspeaker as a function of the mass of the
`cone.
`
`-
`
`loudspeaker as a
`‘
`'
`'
`7
`-
`.
`I
`1
`th
`5 reiatwe output of a ‘t; pical direct radiator
`ffhe weight of the cone is shown in Fig. 6.4.
`In this exam}? 5:
`9
`-
`th
`‘the permanent magnet was kept constant. However,
`e mass
`ecoil and the air gap were selected to obtain maximum output.
`
`--Lvimnampsww
`-
`-
`f(:téIf:C::d)}€I:€711l:;:'7::gA“;)-
`Eng. Soc» Vol- 2: Ne 4- P- 219: 1954-
`
`In terms of the resistivity and density of the voice coil, equa
`becomes
`-
`'
`
`_
`“ r
`
`BZTMAWL1
`
`X 1°“
`
`p
`
`K,
`
`mass of the voice coil, in grams,
`density of the voice coil conductor, in grams per cubi
`‘ meter, and
`'
`resistivity of the voice coil conductor, in microhms :v. '.
`meter cube.
`f
`
`The density, resistivity, and density-resistivity product of Va"-
`ments are shown in Table 6.1.
`3- 'i_
`
`TABLE 6.1, DENSITY p, in GRAMS PER CUBIC CENTIMETER; RESISTIVITY K,, IN 2.
`PER CENTIMETER CUBE AND DE.\'sii'Y—REs1s'r1vri'Y pnonucr PK, or VARIOUS
`J
`TEMPERATURE, 20° C.
`
`'
`
`Element
`
`N
`
`Sodium
`Lithium
`Potassium
`Calcium
`Aluminum
`Magnesium .
`Titanium
`Copper
`.
`Silver
`Chromium
`Beryllium .
`Barium
`Manganese
`Caesium
`Zinc
`.
`Gold
`Molybdenum
`Cadmium
`Nickel
`.
`Iron
`Cobalt
`.
`Tin
`Tungsten
`lridiurn
`Platinum
`Lead
`Antimony
`Bismuth
`Mercury
`
`.
`
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`£:xLimE:nmoxI_-ZnoxwereN
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`xxoxiooou-u.uu\xoooo—>\i:xox~.>'ooeI—E3xV'''
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`
`The relation between the efficiency and the ratio of the mass of‘
`coil to the mass of the cone and the air load may be obtained from"
`6.7 and is depicted in Fig. 6.3. The maximum efficiency occursgw
`mass of the voice coil is equal to the mass of the cone and air load‘
`‘-
`
`.
`
`THX Ltd. Exhibit 2010 Page 7
`IPR2014-00235
`
`

`
`130
`
`ACOUSTICAL ENGINEERING
`
`There is a limit to the extent to which the reduction in mass of the cone can
`be carried because, as the cone mass is reduced, the strength of the cone;
`reduced and as a consequence the nonlinear distortion is increased due 'r_
`overload of the material of the cone. High sensitivity and low distortio
`are not compatible.
`In order to obtain low nonlinear distortion, a relative
`heavy cone must be used. The subject of nonlinear distortion and con_
`weight will be discussed in Sec. 626.
`.
`The mechanical impedance and corresponding efficiency characteristi
`assuming the mechanical reactance due to the suspension to be zero a 5
`shown in Fig. 6.2. The air load mechanical resistance and mechanic
`reactance are assumed to be the same as those on two sides of a vibratin
`piston with the diameter equal to the cone diameter (see Sec. 5.8). The
`weights of the cones and voice coils are typical of loudspeakers ‘in actua
`use today.
`It will be seen that the efficiencies of all three systems at
`practically the same. Of course, the power-handling capacity of the smalle
`cones is very small at the lower frequencies.
`‘
`In the preceding considerations the mechanical reactance due to th‘
`suspension system was assumed to be zero. The efficiency in which all
`the elements of the vibrating system are included may be obtained from
`equation 6.5. The mechanical, resistance 7M0, due to the suspension syste
`is also a factor in the efficiency in the region of resonance. Typical Valu
`of mm for 16-, 4~, and 1—inch cones are shown in Fig. 6.2. The efficient"
`'=
`characteristics under these conditions are shown in Fig. 6.2.
`It will
`u
`noted that
`the efficiency is high at
`the resonant frequency. Howeve -
`when coupled to a vacuum tube driving system the motional electrica
`impedance is also increased which reduces the power input to the Voi
`'
`coil. For this reason the response is not accentuated to the degree depict
`by the peak in the efficiency characteristic.
`It will be seen that t‘
`efficiency decreases very rapidly below the resonant frequency. Th
`fore, in a direct radiator loudspeaker the limit at the low—frequency e .-.
`of the frequency range is determined by the resonant frequency of th
`system.
`'
`The motional electrical impedance of a dynamic loudspeaker is give
`by equation 6.3. The normal electrical impedance, in abohms, of voi 1'
`coil is given by
`:
`6;
`
`ZEN = ZEM + ZED
`
`_
`
`where zEM motional electrical impedance, in abohms, and
`253 — electrical impedance of the voice coil in the absence of motio
`that is blocked, in abohms.
`
`impedance are shown i
`the motional electrical
`The components of
`Fig. 6.5. At the resonant frequency the motional electrical impedance fs
`large because the mechanical impedance is small. The current in the voice‘
`coil circuit may be determined from the voice coil electrical circuit,
`the
`driving voltage and the electrical resistance of the generator.
`
`_ _l3l
`DIRECT RADIATOR LOUDSPEAKBRS
`J he mecharnotive force or driving force,5 in dynes, applied to the mechan-
`system is
`_
`fM = Bh
`
`"'i ere B = flux density in the air gap, in gausses,
`I
`Z — length of the conductor, in centimeters, and
`1' = current in the voice coil circuit, in abamperes.
`
`‘,i_is is the driving force, fM, applied to the mechanical system as shown in
`:a_ 6.1.
`
`- ZEN: Z:n+Zan
`
`OHM5
`IN
`
`IMPEDANCE
`
`FREQUENCY
`
`FREQUENCY
`
`"he electrical impedance characteristics of the voice coil in a direct
`FIG. 6.5.
`.' _mdiato1— loudspeaker. 3“, = the normal
`electrical
`impedance. 2“, = the
`‘I damped
`electrical
`impedance.
`.7”, = the motional
`electrical
`impedance.
`-7“, = the resistive component of the motional electrical
`impedance.
`xm, -—-
`the reactive component of the motional electrical impedance.
`
`'
`
`"" The mechanical impedance,5 in mechanical ohms, due to the electrical
`._ icuit is
`.
`
`6.10
`
`F. 3 re ZET = 730 + jwl + 7120,
`I ma 2 damped electrical resistance of the voice coil, in abohms,
`L = damped inductance of the voice coil in abhenries, and
`ma = electrical resistance of the generator, in abohms.
`
`his mechanical impedance appears in the mechanical system as shown in
`ig. 6.1.
`In calculating the steady state performance the driving force,
`‘
`',, applied to the mechanical system is used and the mechanical impedance
`to the electrical system need not be considered. However, in comput-
`_'g the transient response of the system, the damping constant, etc., the
`'5 Olson, "Dynamical Analogies," D. Van Nostrand Company, Princeton, NJ»
`‘I
`§43.
`L 5 Ibid.
`
`THX Ltd. Exhibit 2010 Page 8
`IPR2014-00235
`
`

`
`132
`
`ACOUSTICAL ENGINEERING
`
`mechanical impedance due to the electrical circuit must be included. T
`driving force of the generator in the mechanical system which will prod
`a force, fM, across the mechanical system is
`_/IMZME
`fMo = fM + ZMT
`
`The increase of electrical impedance of the voice coil, with frequency, i 3_
`combination with the existing vacuum tube driving system,
`is anot
`-
`factor which reduces the response of a dynamic loudspeaker at the higli
`frequencies. The electrical impedance characteristics of the vacuum tub
`power amplifiers are generally designed so that the voltage across the lou
`_
`speaker, for constant voltage applied to the input of the power stage
`independent of the frequency. Therefore,
`the current in the voice co"i
`decreases with frequency as the electrical impedance increases with fr‘
`quency. The electrical
`impedance frequency characteristics of severa
`voice coils are shown in Fig. 6.6.
`In the case of a large, heavy Voice coil"
`
`1
`
`DIRECT RADIATOR LOUDSPEAKERS
`
`-
`
`l33
`
`-the directional becomes sharper with increase in frequency. However,
`‘piston directional pattern cannot be used because there is considerable
`iation from piston action in a cone loudspeaker. Measured directional
`L0
`’
`‘
`facteristics of direct radiator loudspeakers, having thf constants given
`
`ndki
`soon rv
`
`°°
`
`8 3
`
`0
`
`ill
`
`#'iii'
`
`FREQUENCY IN CYCLES PER SECOND
`
`'
`
`in
`Er0
`no
`Eo.4A.
`.<
`‘_’c:r-uu.1....
`
`E_
`
`Zi
`
`FIG. 6.6. The electrical impedance characteristics of ‘lé-inch diameter voice coils of 140,‘-
`70, and 18 turns and all having 10 ohms d—c resistance.
`
`impedance at the higher frequencies:
`the rapid increase of the electrical
`causes a corresponding reduction in the driving force. To maintain the ,'
`driving force at the higher frequencies requires a relatively low ratio of the'_ '
`inductive electrical reactance to the electrical resistance which for 3. con=
`stant value of the electrical resistance is equivalent to a reduction in the
`mass of the voice coil.
`_——,
`The response of a loudspeaker is a measure of the sound pressure produce
`at a designated position in the medium withthe electrical input, frequency‘ .
`and acoustic conditions specified.
`In general, the response is obtained on the-
`axis of the cone.
`If the loudspeaker were nondirectional, the efficienc _
`characteristic would also be the response frequency characteristic. The‘
`system is not nondirectional but is similar to that of a vibrating piston, in’,
`
`. 6.8. Directional characteristics of a dynamic, direct radiator loudspeaker with a.
`-. 0° cone 16 inches in diameter, mounted in a large baffle.
`
`-
`
`’Fig. 6.2, are shown in Figs. 6.? and 6.8. Employing the mechanical
`g uit and the electrical circuit of Fig. 6.1 and the data of Fig. 6.2, the total
`tput of the loudspeaker may be determined as outlined in this section.
`s quite obvious that the response on the axis will be accentuated at
`the
`_-li gh frequencies. due to the sharpening of the directional pattern.
`
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`
`

`
`134
`
`ACOUSTICAL ENGINEERING
`
`DIRECT RADIATOR LOUDSPEAKERS
`
`135
`
`The power output of a loudspeaker may be obtained from the direc-
`tional pattern and the response frequency characteristic by considering the
`sound flow through a spherical surface in which the loudspeaker is located
`at the center (see Sec. 10.3D1). The surface is divided into incremental
`areas and the power transmitted through each area is determined from the
`sound pressure. The total power is equal
`to the summation of the in-
`cremental areas and may be expressed as
`
`P = Ejafpids
`pC
`- total power, in watts,
`density of the medium, in grams per cubic centimeter,
`p
`Velocity of sound in the medium, in centimeters per second,
`5
`15 = root mean square sound pressure over the element of area db‘,
`in dynes per square centimeter, and
`d5 = element of area on the spherical surface, in square centimeters.
`
`6.12
`
`In the case under consideration the power output, P, as a function of
`the frequency may be determined from equation 6.5 and the electrical
`input. The directional patterns for the cones having diameters of 4 and
`16 inches are shown in Figs. 6.7 and 6.8. From these data, the pressure
`on the axis may be determined from equation 6.12. The computed re-
`sponse frequency characteristics of the loudspeakers of Fig. 6.2 are shown
`in Fig. 6.9. These characteristics are quite similar to the actual response
`frequency characteristics.
`Another factor of interest in a direct radiator is the power handling
`capacity. The sound power output, in watts, is given by
`
`6.13
`P : (rMAa&2)1O‘7
`where 7;,” mechanical resistance,
`in mechanical ohms, obtained from
`Sec. 5.8, and
`root—mean-square velocity of the piston,
`second.
`
`in centimeters per
`
`Equation 6.13 may be used to compute the power output of a direct
`radiator loudspeaker in the region were all parts of the cone move in phase.
`In general, the output is limited by the permissible amplitude. The greatest
`amplitude occurs at the low frequencies where the action is essentially that
`of a piston. Therefore, piston action may be assumed.
`The peak amplitude characteristics of a 16-inch, a 4-inch, and a 1-inch
`piston mounted in an infinite baffle for 1 watt of sound output are shown
`in Fig. 6.10. These characteristics show that
`for practical amplitudes
`a relatively large piston is required to deliver adequate power at the low
`frequencies.
`The directional pattern of a vibrating paper cone depends on three
`principal factors:
`the cone diameter, the cone angle, and the frequency.
`
`the corrugations,
`the processing,
`Other factors, such as the paper pulp,
`the voice coil diameter, and the suspension also influence the directional
`pattern, but in a lesser degree. The directional patterns for various fre-
`quencies of 110° cones having diameters of 4- and 16 inches are shown in
`A
`B
`
`mo
`Ao
`L.
`
`RESPONSEDB vu
`.5 /y
`
`°__sz
`
`.
`
`A
`aro‘2
`
`‘
`
`no‘:
`
`A
`“I032
`raeou: NCY
`
`u.
`>
`
`..0
`
`.._°
`
`(.4
`No
`8
`
`RESPONSEDB
`
`RESPONSEDB
`
`A
`
`B
`
`2
`
`we
`
`FREQUENCY
`
`.
`.1
`B
`to‘
`
`2
`
`4
`
`1
`2
`
`l
`4
`
`8
`
`so’
`rnrquzncr
`
`FIG. 6.9. Pressure response frequency characteristics of the loudspeakers of Fig. 6.2
`having cone ciarneters of 1 inch, 4 inches, anc 16 inches.
`.,_
`_a...
`7"“.
`i|_-
`
`CHES5:
`
`
`
` '1anyAMPLITUDEININ
`
`
`
`505'tn2
`
`2
`
`3
`
`2
`A sansslos
`3
`2
`4 ss7'e"$'lo2
`FREQUENCY IN CYCLES PER SECOND
`
`3
`
`l
`|
`l
`-
`.
`4 56'Hi9'OA
`
`FIG. 6.10. The amplitude frequency characteristics of vibrating pistons
`of various diameters, mounted in an infinite wall, for l~watt output on
`one side.
`
`the directional pattern becomes
`It will be see that
`Figs. 6.7 and 6.8.
`sharper with increase in frequency. However, the pattern is broader than
`that of a vibrating piston of the same diameter due to the relatively low
`velocity of propagation of sound in the paper cone. The directional patterns
`
`THX Ltd. Exhibit 2010 Page 10
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`
`

`
`136
`
`ACOUSTICAL ENGINEERING
`
`DIRECT RADIATOR LOUDSPEAKERS
`
`137
`
`It
`of 130° and 100° cones -1 inches in diameter are shown in Fig. 6.11.
`will be seen that the directional pattern at the high frequencies becomes-
`broader as the cone angle is increased. This is to be expected because the,
`velocity of propagation of sound in the paper cone is about two times"
`the velocity of sound in air. Under these conditions the delay between the
`sound emitted from the outside and the center of the cone will increase as
`the angle of the cone is increased. As a result the directional pattern will.’ :_
`be broadest for the cone with the widest angle. The preceding observations - .
`
`' cycles) requires a relatively large diameter, heavy diaphragm, and large
`E coil at the lower frequencies, and a relatively light diaphragm and coil to
`I obtain good efficiencies at the higher frequencies. There are a number of
`_ direct radiator loudspeaker systems which may be built to satisfy these
`, conditions.
`It is the purpose of the sections which follow to consider a
`' number of these systems.
`Sing1e—Coil Loudspeaker.—Several
`6.3. Multiple
`Sing1e—Cone,
`' arrangements for obtaining uniform response, broad directional pattern,
`adequate power handling capacity, and tolerable efliciency are shown in
`Fig. 6.12.
`The systems of Fig. 6.12A, C, and D consist of a large diameter heavy
`cone driven by large voice coil for the low—frequency range and a small
`
`Pro. 6.11. Directional characteristics of dynamic direct radiator loudspeakers with
`cones 4 inches in diameter for two different cone angles. Row A. 130° cone. Row B.- _'
`100° cone.
`
`K
`
`with regard to cone type vibrators may be substantiated by theoretical
`considerations as outlined in Sec. 2.21.
`The characteristics of Figs. 6.2 and 6.9 show that the low—frequency"'.
`efficiency may be maintained to the higher frequency ranges by employing .
`a small and relatively light weight cone and voice coil. On the other hand,-..
`_
`to obtain adequate power handling capacity at the low frequencies With- -
`tolerable excursions of the vibrating system requires a cone of relatively'--- '
`large area. To insure operation below the elastic limits of the materials, -
`a cone of large area must be of sturdy construction. Equation 6.7 and Fig_.;._
`-
`6.3 show that a large heavy cone also requires a relatively large voice coil '
`in order to maintain a tolerable efficiency. The efficiency of this system _
`is low in the high-frequency range. Furthermore, the directional pattern.
`'
`of a large cone becomes quite narrow in the high-frequency range. Vi/here; '
`the frequency range is confined within the limits of from 80 cycles to *'
`4000 cycles, satisfactory efficiency, response, and directional characteristics;
`can be obtained from a sing1e—cone, single—coil loudspeaker. The above"
`discussions show that
`to obtain adequate power handling capacity and —_
`uniform response over a wide frequency range (greater than 80 to 4000
`
`.
`
`L.F. UNIT
`
`H.F, UNIT
`
`©
`
`FIG. 6.12. Multiple single—cone, single-coil, direct radiator, dynamic, loud-
`speaker systems. A, C, and D. Large low-frequency unit, small high-
`frequency unit, and filter system. B. Seven small units connected in parallel.
`
`‘diameter light cone and small voice coil for the high—frequency range and
`. a filter system for allocating the power in the high- and low—frequency ranges
`-'.to the respective low— and high—frequency units. The filter system consists
`of an inductance in series with the low—frequency unit and a condenser in
`series with the high—frequency unit. Due to the large inductance of the
`arge voice coil, as shown in Fig. 6.6, it has been found that for most applica-
`tions the inductance in series with the low-frequency unit may be omitted.
`'
`:.On the other hand, if a more elaborate filter system is required, the circuit
`_‘, of Fig. 7.16 may be used.
`
`THX Ltd. Exhibit 2010 Page 11
`IPR2014-00235
`
`

`
`138
`
`ACOUSTICAL ENGINEERING
`
`DIRECT RADIATOR LOUDSPEAKERS
`
`139
`
`I
`
`In Fig. 6.12A the low- and high—frequency units are separated by a
`relatively large distance.
`In the overlap frequency region this distance
`may be more than 1 wavelength. The directional patterns of two sources
`shown in Fig. 2.3 are applicable to this system. These characteristics
`show that two separated sources exhibit directional patterns with one or
`more lobes with very low response between the lobes. The result is fre-
`quency discrimination, for points removed from the axis,
`in the overlap
`region.
`This condition is reduced in Fig. 6.12C but
`is not eliminated.
`However, a disadvantage of the system of Fig. 6.l2C is that sound diffracts
`around the high-frequency unit and is reflected from the large cone causing
`a ragged response due to interference between the direct and reflected sound. '
`The objectional features of Fig, 6.12A and C referred to above have v
`-
`In this system7 the large cone is geo-
`been eliminated in Fig. 6.12D.
`Therefore,
`in the overlap 5
`the small cone.
`metrically a continuation of
`:5" DIAMETER CONE
`
`.
`
`lrssponsroa
`
`I200 CVCLES
`
`5000 CVCLES
`
`FIG. 6.13. Directional characteristics of direct radiator loudspeakers with
`cone diameters of 15 inches and 2.5 inches.
`
`In this way phase_
`
`region the two cones vibrate together as a single cone.
`and diffraction effects are eliminated.
`In a two-unit loudspeaker, employing a large cone for the reproduction of ';
`the low—frequency range and a small cone for the reproduction of the high— ,‘
`frequency range, a uniform directivity pattern can'be obtained over the 1‘
`entire audio—frequency range. This has been described in connection with
`Figs. 6.6 and 6.7. This is illustrated further in Fig. 6.13 in which the
`directivity patterns of 15-inch and 2%-inch cone loudspeakers are compared ‘'
`for a six to one ratio of frequency, that is, for a constant ratio of diameter
`to wavelength.
`Fig. 6.13 shows that the directivity pattern of a 15-inch
`loudspeaker at 200 to 1000 cycles corresponds to that of a 2§—inch
`7 Olson and Preston, RCA Review, Vol. 7, No. 2, p. 155, 1946.
`
`These relationships were used in
`loudspeaker at 1200 and 6000 cycles.
`designing the two units of the system shown in Fig. 6.121).
`In the loudspeaker3>9 shown in Fig. 6.l2D, small cones may be attached
`to the large cone to reduce the velocity of wave propagation in the large
`cone.
`Fig. 6.14. This broadens the directivity pattern of the low—frequency
`cone.
`In the high-frequency range,
`the conical domes attached to the
`surface of the low-frequency cone improve the performance in three ways:
`by decreasing the angle into which.the high-frequency cone feeds, thereby
`increasing the output of
`the high-
`, frequency cone; by diffusely reflecting
`‘_ some of the sound emitted by the high-
`frequency cone,
`thereby eliminating
`,- discrete reflections; and by diffracting
`'3 some of the sound emitted by the high-
`"
`frequency cone, thereby broadening the
`' directivity pattern.
`The angles
`into which the high-
`frequency cone feeds, without and with
`‘
`,-J the conical domes applied to the low-
`. frequency cone of
`6.14, are desig-
`l mated as (£31 and gig in Fig‘. 6.l5A and
`Fig. 6.15B.
`Since z,-lag is smaller than «#1,
`the acoustic radiation load upon the
`" cone is greater with the conical domes
`‘
`‘ than without them. When the acoustic
`' radiation load upon a direct radiator
`loudspeaker
`is
`increased,
`the sound
`power output is increased. Thus, it will
`be seen that the conical domes increase
`the high-frequency sound radiated by
`the high'frequency Cone"
`In other
`W0fd5, the hlgh’frequenCy efficiency is
`improved.
`the sound emitted by the
`Some of
`high—frequency cone is diffusely reflected by the conical domes, as shown in
`; 5‘ Fig. 6.16. Without the domes, there would be many similar reflections
`2
`-
`I, which would lead to reinforcements and cancellations with the direct radia-
`i_-J ' tion. The result would be corresponding peaks and