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Fundamentals of Audio Production, Chapter 10

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Fundamentals of Audio Fundamentals of Audio ProductionProduction

Chapter Ten:Chapter Ten:

LoudspeakersLoudspeakers


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Loudspeakers as transducers

• The speaker converts electrical energy The speaker converts electrical energy into physical energyinto physical energy

• Alternating electrical current causes the Alternating electrical current causes the voice coil to move in relation to a voice coil to move in relation to a permanent magnetpermanent magnet

• Movements in the coil are transferred to a Movements in the coil are transferred to a diaphragm or cone, which create diaphragm or cone, which create movements in air moleculesmovements in air molecules


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Voice CoilVoice CoilPermanent magnetPermanent magnet

Voice coilVoice coil

Dust Dust covercover

Dust Dust covercover


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Elements of the LoudspeakerElements of the Loudspeaker

Voice CoilVoice Coil

Permanent Permanent MagnetMagnet

SpiderSpider

Coil FormCoil Form

Dust CoverDust Cover


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Elements of the LoudspeakerElements of the Loudspeaker


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Speaker operationSpeaker operation


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EnclosuresEnclosures

• Speakers lack efficiency in converting Speakers lack efficiency in converting electricity into audio energyelectricity into audio energy

• Placing the speaker inside an enclosure Placing the speaker inside an enclosure improves its efficiencyimproves its efficiency


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EnclosuresEnclosures


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Compression DriversCompression Drivers

• Compression drivers operate on the same Compression drivers operate on the same principle, but are attached to hornsprinciple, but are attached to horns

• Horns increase the efficiency of the driver Horns increase the efficiency of the driver by enhancing sound wave propagationby enhancing sound wave propagation

• The result is that horns “sound louder” with The result is that horns “sound louder” with the same level of amplificationthe same level of amplification


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Compression DriversCompression Drivers

DriverDriverHorn Horn MouthMouth

Horn Horn ThroatThroat


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Alternative driver designsAlternative driver designsElectrostatic driver designElectrostatic driver design


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Crossover NetworksCrossover Networks

• Crossovers separate the signal into Crossovers separate the signal into component frequencies which are routed component frequencies which are routed to individual driversto individual drivers

• Separating the frequencies allows the Separating the frequencies allows the drivers to be more efficient and protects drivers to be more efficient and protects them from being overdriventhem from being overdriven


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Crossover NetworksCrossover Networks

• Crossovers may be Crossovers may be passive passive which are which are internal – inside the speaker enclosureinternal – inside the speaker enclosure– Passive crossovers have fixed crossover Passive crossovers have fixed crossover

frequenciesfrequencies

• Crossovers may also be Crossovers may also be active active which are which are outboard units that are user adjustableoutboard units that are user adjustable– Active crossovers are used in bi-amplifying or Active crossovers are used in bi-amplifying or

tri-amplifying sound systemstri-amplifying sound systems


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Tri-amplified sound systemTri-amplified sound system


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Three and four way systemsThree and four way systems

• Tweeters reproduce high frequencies Tweeters reproduce high frequencies (above 5 KHz)(above 5 KHz)

• Mid-range drivers reproduce middle Mid-range drivers reproduce middle frequencies (1-2 KHz)frequencies (1-2 KHz)

• Woofers reproduce low frequencies (below Woofers reproduce low frequencies (below 1) KHz1) KHz

• Sub-woofers reproduce very low Sub-woofers reproduce very low frequencies (below 100 Hz)frequencies (below 100 Hz)


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Speaker PlacementSpeaker Placement

• Studio monitors Studio monitors should be placed should be placed equidistant from the equidistant from the listenerlistener


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Speaker PlacementSpeaker Placement

• Speaker distances may be described asSpeaker distances may be described as– Far fieldFar field– Mid fieldMid field– Near fieldNear field– Ultra near fieldUltra near field


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Speaker PlacementSpeaker PlacementTraditional “side stack” speakers for live soundTraditional “side stack” speakers for live sound


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Speaker PlacementSpeaker Placement““Central Cluster” for live soundCentral Cluster” for live sound


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ImpedanceImpedance

• ElectricalElectrical impedance is the reluctance for impedance is the reluctance for alternating current to flow in a voice coilalternating current to flow in a voice coil

• MechanicalMechanical impedance is the physical impedance is the physical opposition for the speaker cone or opposition for the speaker cone or diaphragm to movediaphragm to move

• Acoustic radiationAcoustic radiation impedance refers to impedance refers to how efficiently the speaker moves airhow efficiently the speaker moves air


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• Speaker impedance must be matched closely to the amplifier’s output impedance to avoid damaging the amplifier, and to increase system efficiency

• As speaker impedance drops, current flow increases, causing overheating of the amplifier components

ImpedanceImpedance