INTRODUCTION
Theprimaryrequirementofleft/center/rightmainchannel
cinemaloudspeakersisthattheyfaithfullyreproducethe
entireaudiospectrumfrom20Hzto20 kHz. While crisp,
naturalreproductionofthevocalrange(300 Hz - 2 kHz) has
always beencriticaltogoodcinemasound,veryhighand
verylowfrequencies(above 4 kHz and below200Hz)
demandparticularattentionintheageofdigitalcinema
audio.Theadventofdigitaltechnologyhasbroughtsound
effectstotheveryextremesofhearing,fillingtheseranges
withsonicmaterialwhichtodaydefinesthedigitalage
cinemaexperience.
Traditionaltwo-way cinema loudspeaker design (a large
conewooferandahorn-loadedhighfrequencycompression
driver)suffersfromanunfortunate500 Hz crossoverplace-
mentthatrobsdialogofmuchofitswarmth.Byrequiring
thehighfrequencycompressiondrivertocover frequencies
aslowas500 Hz, two-waydesignintroducessubstantial,
audibledistortioninthevocalregion,leaving voices sound-
ingharshandhollow.
Similarly, a 500Hzcrossovercompromisesaloudspeak-
er’sreproductionofextremehighandlow frequencies.
Transducers(coneorcompressiondrivers) haveoptimal
rangesinwhichtheyaremost“comfortable” and reproduce
soundmosteasily. When a driverisaskedtogobeyondits
“comfortzone,” distortion and/or inadequate response
result.Whileitispossibleforatwo-way design to employ
driversthatcoverextremehighsandlowsadequately, it
wouldrequiresacrificingresponseinotherfrequencyranges
–notablythevocalrange.
Finally, for a traditional two-waycinemaloudspeakerto
achieveadequatepatterncontrolfrom500Hzto20kHz,
thehorn’sthroatmustbeofsuchasizethatcancellations
withinthethroataddyetmoredistortion,typicallyinthe
700 Hz range.
Thispaperwillendeavor to show that bydedicatinga
subsystemtothevocalregion,three-wayloudspeakersare
betterabletohandlethenewdemandsofdigitallyedited,
mixedandencodedsoundtracks.Comparedtotwo-way
designs,three-wayloudspeakersimprove vocalclarityand
warmth,reducedistortionfrombothhorn-throatcancella-
tionanddriverexcursion,increasetheloudspeaker’s power
handlingcapability, and improvesperformanceacrossthe
audiospectrumincludingextremehighsandlows.
DIVIDING THE AUDIO SPECTRUM
Theaudiblespectrumspansjustunder10octaves ranging
from20Hzto20kHz(20,000Hz).Frequencyismeasured
accordingtoalogarithmicscale;foreachoctaveascended,
frequencydoubles.Ifmiddle“C”is300Hz,thenthe“C”
aboveitwouldbe600Hzandthe“C”below, 150Hz.
Sinceasingletransducercanonlyeffectivelycoverso
muchofthisrange,two-wayandthree-wayloudspeakersys-
temsdividetherangeintohigh/low-andhigh/mid/low-fre-
quencysections,respectively.
Ourresearchandexperiencehaveshownthatasingle
transducer’scomfortzoneusuallyspansnomorethanthree
andahalfoctaves.Yettraditional500Hzcrossoverdesign
requiresthehighfrequencycompressiondrivertocover well
inexcessoffiveoctaves.
Whilecompressiondriversreproducefrequenciesabove
1kHzquitewell,muchhigherdistortionresultbelow that
pointduetoexcessivedriverexcursion.Criticalvocalmateri-
alinthecompressiondriver’slowest octave(500-1000Hz)
fallsoutsidethedriver’scomfortzone. The resulting distor-
tiongivesvoicesaharsh,unnaturaledgesometimesrender-
ingthemunintelligible.Onecannotoveremphasize the
importancethisholdsforcinemasound;withoutintelligi-
bledialog,thecinematicexperienceismeaningless.
Bydedicatingasubsystemtothemidfrequencyrange,
three-wayloudspeakerseffectivelyeliminatetheseprob-
lems.EAW’sthree-waydesignsuselargeconewoofers,cone
drivenmidrangesubsystems and horn-loaded high frequen-
cycompressiondrivers.Weplacecrossoverpointsatspecific
frequenciesselectedtooptimizetheperformanceofeach
particularloudspeakersystem.Ingeneral,thelow/mid
crossoverissetaround350Hzandthemid/highcrossover
around2kHz.
Simplyaddinganotherhorn-loadedcompressiondriver
tocoverthemidfrequencyrangedoesnoteliminatedistor-
tionfromthevocalrange;infact,itaggravates the problem.
Ifexcessivedriverexcursionat500Hzcausesacompression
drivertointroducesignificantdistortion,distortionat300
Hzwillbeevengreater. To eliminate distortion from the
20 100 1000 10000 20000
dB SPL
Frequency (Hz)
Traditional 2-way loudspeaker design
vocal range
woofer compression driver
20 100 1000 10000 20000
dB SPL
Frequency (Hz)
EAW 3-way loudspeaker design
vocal range
woofer compression drivermidrange cone
