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69 Cards in this Set
- Front
- Back
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define the dynamic range of a system
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Difference in decibel between noise floor and the system's maximum output before distortion
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define the noise floor of a live sound system
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The amount of noise surrounding a system (i.e. planes, trains, automobiles) when there is no sound going through
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define a live sound headroom
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The difference between the softest and the loudest mix before distortion
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Why do your master outputs have to be set to unity gain?
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It prevents the amps from being underloaded
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What is white noise?
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The sound of the electrons moving within a system
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What is the difference between white noise and pink noise?
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White noise contains a 3dB increase of energy per octave.
Pink noise has equal energy at every frequency |
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What causes popcorn noise?
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Dirt, debris, and poor system maintenance
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What causes harmonic distortion?
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Excessive EQ on a weak passive system
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What are the 4 kinds of noise that can be caused by a live sound system?
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White noise
pink noise popcorn noise harmonic distortion |
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What is a transducer?
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anything that changes one type of energy to another
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What is the speed of sound?
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1130 ft/second or 740 mph
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What is the speed of light?
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186,242 miles per second
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What advantage does a horn have over a direct radiator?
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The throat of a horn produces a natural compression
the horn gives total control over the directional pattern |
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Why would you place the horn below a direct radiator in a speaker?
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to stop the bass from traveling too far
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What is a common name for a direct radiator?
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Woofer
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What happens when natural elements hit the rear of a driver?
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the voice coil goes into extra movements causing distortion
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What happens when resonating frequencies escape the rear of a driver?
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They move to the front and cause frequency cancellation
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Why would you put a port on a speaker enclosure?
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to re-enforce the sound of the low end frequencies
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What does the diameter of a port determine?
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which frequencies will be allowed to escape.. dependent on wavelength
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What does the length of a port determine?
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The sound delay. Prevents phase cancellation
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What method of transduction do all speakers use?
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Electromagnetic
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what causes the stationary magnetic field in a speaker?
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the voice coil surrounded by the magnet
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What causes the secondary magnetic field in a speaker?
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amplifier output through the voice coil
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What determines the polarity of the speaker's secondary magnetic field?
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The amplifier output
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What causes the actual transduction of a speaker?
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The interaction between the stationary and secondary magnetic fields
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What are the 9 components of a speaker?
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Pole piece
magnet gap basket spider former voice coil cone dome |
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Define Voice Coil
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A flat cable wrapped around the former
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What does the former consist of?
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Chemically treated heat resistant cardboard
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Describe a stationary speaker magnet
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donut shaped
fitted top to bottom with two steel plates |
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What is the pole piece?
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A steel rod inserted in the donut shaped magnet
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What is the home of the voice coil?
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The gap between the magnet and the pole piece
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What is the dome?
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The dust cover over the gap
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What two things does the spider do?
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Attaches the voice coil to the cone and the dome
Allows easy suspension to the voice coil |
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Where does the speaker cone attach to?
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The basket
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What is the speaker basket?
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The actual physical shape of the driver
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what are the 4 speaker specifications?
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Frequency response
Power handling Sensitivity Impedance |
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Define a frequency response
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A component's ability to produce an output signal with the same frequency range as the input signal
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What is a typical speaker margin of error?
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+/- 3dB
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What is a typical amplifier margin of error?
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+/- 1dB
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What is a speaker or amp's state of tolerance?
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The ability to produce an intended frequency response within a margin of error
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What are the three ratings that determine a speaker's power handling capabilities?
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Continuous rating
Program rating Peak rating |
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How do you test the continuous rating of a speaker?
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send a continuous low level sound through it to see how well the voice coil can handle the heat
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What is the program rating of a speaker used for?
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matching the power to the amplifier
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How is a speaker's peak rating determined?
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put a very loud signal to the speaker for 1/10th of a second
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What are the three test levels that determine a speaker's sensitivity?
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1 watt @ meter
1 watt @ 4 feet 1 milliwatt @ 30 feet |
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What is the difference between impedance and resistance?
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Impedance is the opposition to electrons in an AC circuit
Resistance is the opposition to electrons in a DC circuit |
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What are the three types of impedance?
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Source Impedance
Load Impedance Nominal Impedance |
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What is the source impedance?
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Impedance of the amplifier
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What is the load impedance?
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Impedance of the speaker
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What is the nominal impedance?
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The lowest amount of impedance the speaker will present to the amp
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when doing a show, are speakers hooked up in series or parallel?
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parallel ALWAYS!!
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What is the measurement for current?
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amps (i)
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What is the measurement for impedance?
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ohms (z)
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What is the measurement for power?
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Watts (p)
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What is the measurement for pressure?
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Volts (v)
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What is the ohm's law formula for current?
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I=v/z
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What is the ohm's law formula for power?
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P=i*v
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What are the steps for calculating net impedance from a parallel setup?
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1) invert each speaker's impedance (i.e. 8 ohms speaker becomes 1/8)
2) add the fractions for all speakers 3) invert the sum of the fractions 4) divide the denominator into the numerator The total is your net impedance |
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how do you calculate net impedance for a series setup?
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add the speaker impedances together
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What happens when you cut the impedance in half?
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You double the wattage
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Why can't you connect an 8 ohm amp to a 4 ohm speaker?
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load impedance cannot be lower than the source impedance
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Under the insertion laws how many watts does one dB equal?
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1dB=21 Watts
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What is the insertion law?
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Loss of no more than 1dB of signal in a passive crossover due to the heat of the fundamental electronic components.
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What is the difference between a crossover cutoff point and the flat range of signal?
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-3dB
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What is a crossover slope?
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The rate at which the frequency to its own intended driver will start to gradually fall off after the cutoff frequency point
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What is the rate of a professional crossover's slope?
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24dB/octave
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What is the rate of a semi-professional crossover's slope?
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18dB/octave
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What is the rate of a first order consumer crossover's slope?
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6dB/octave
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What is the rate of a second order consumer crossover's slope?
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12dB/octave
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