Amplifiers and Speakers Tufts University – ME 93 October 8, 2015.
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Transcript of Amplifiers and Speakers Tufts University – ME 93 October 8, 2015.
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Amplifiers and SpeakersTufts University – ME 93October 8, 2015
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What is a speaker?
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When is a speaker a mic?
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Signal Level
Mic Level5-50 mV
Line Level
50 mV – 2V
Speaker Level50-100V
Preamp Poweramp
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Signal Level - Voltage
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What about Watts?Watts measure Power (P)Volts measure Voltage (E)Amps measure Current (I)
Ohms measure Impedance (R)
P = E * I
I =
ER
A microphone with a RMS voltage of: 0.05 Volts and an impedance of: 200 Ohms
draws a current of: 0.0025 Amps
exerts an average power around: 0.0000125 Watts
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Signal Level - Watts
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The Passive Speaker Cabinet• 1 or more speakers• Crossover• Most be paired with
an external amplifier• Dampening• The Cabinet
• Grille• Port
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Passive Crossovers
Amplifier
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Active Crossovers
Amplifier
Amplifier
Amplifier
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The Active Speaker Cabinet• 1 or more speakers• Active crossover• Has it’s own amplifier(s)• Dampening• The Cabinet
• Grille• Port
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Speaker Specifications• Frequency Response• Power rating• dBSPL = 1 watt of power @ 1 meter away
• Impedance• Directionality and dispersion• coverage angle
• Weight/Form Factor• Rigging components
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Amplifier Specifications• Frequency Response• Power Rating• Dependent on impedance of the load• Bridging
• Slew Rate• Damping Factor• Higher is better!
• THD
Stereo 8 Ohms, both channels driven……….240 W/ch
Stereo 4 Ohms, both channels driven……….400 W/ch
Mono 8 Ohms, Bridged………………..……800 W/ch
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Impedance & Power• Multiple loudspeakers will generally be
connected in parallel• How do we calculate the impedance?
Znet
=
11Z1
1Z2
1Zn
+ +
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Impedance & PowerOnly link speakers with the same impedance• divide Z by # of speakers or just keep
dividing by 2 (conservative)
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ParametersPassive Speakers• Driver Attenuators
Amplifiers• Input Sensitivity• Bridging• Filters
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Best Practices• Tweeters don’t like clipping
• Woofers don’t like DC/over-excursion
• Matching amplifers and speakers
• Turn the amplifiers up so you don’t have to turn the mixer up
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Next Steps• Speaker manufacturers close by• EAW• Bose• Genelec