Cycle 3 Test Flashcards
Stereo requires at least 2 microphones to record one source with differences in _______ and ______ between the two mics
amplitude, time of arrival
matched pair
two mics that are manufacturer-tested to be as close to the same mic as possible.
two rules for matched pair mics
- dont use one without the other
2. be careful in high SPL situations
Spaced Pair pros/cons
+ Wide stereo image
- Lacks a strong center
- Phase issues (Use the 3:1 Rule)
XY pros/cons
+ Good phase coherency
+ Strong center
- Image not as wide as a spaced pair
+/- Picks up mostly direct sounds with minimal room sounds
ORTF pros/cons
+ Mimics human hearing
+ Wider image than XY (not as wide as spaced pair)
- Some phase issues (near-coincident)
Mid-Side pros/cons
+ Individual control over direct and room sounds during & after the recording session.
+ Control of stereo width during & after the recording session
+ Good phase coherency
+ Good mono compatibility
- Image not as wide as a spaced pair
Blumlein pros/cons
+ Good phase coherency
+ Strong center
- Image not as wide as spaced pair
+/- Picks up direct sounds AND room sounds
compressor / limiter
a device employing a gain reduction circuit to manipulate or control the dynamic range of an audio signal.
threshold
when the input signal exceeds a pre determined level (the threshold), the compressor’s gain is reduced and the signal is attenuated.
ratio
the amount of input decibels above the threshold, to the amount of output decibels above the threshold.
attack
sets the amount of time it takes for the compressors gain to be reduced.
release
sets the amount of time it takes for the compressor’s gain to return to its original level
bad compressor release settings - side effects
too fast = pumping or breathing effect… rapid rise in noise floor.
too slow = over compression
output/makeup gain
compensates for gain reduction
knee
how strictly the threshold is encorced
around a _____ ratio is where limiting begins (depends on the situation)
4:1
what is the primary difference between a Compressor and a Limiter?
ratio.
famous compressors
- Teletronix LA-2A Optical Style Tube Compressor
2. Universal Audio 1176
Audio EQ is defined as
a device that enables the engineer to exercise control over the harmonic or timbral content of a live or recorded sound.
reasons for EQ (5 reasons)
- to correct specific problems within a “live” signal
- to overcome deficiencies in the frequency response of a microphone or in the sound of an instrument
- to alter a sound purely for creative reasons
- to allow contrasting sounds to blend better in a mix
- to reduce the frequencies that are causing leakage
two types of analog filter circuits
- passive filter EQ
2. active filter EQ
types of EQ filter CURVES (5)
peaking curve, shelving curve, high+low pass filters, bandpass filters
regarding high & low pass filters… frequencies attenuated less than 3db are considered to be
inside the passband
regarding high & low pass filters… frequencies attenuated more than 3dB are said to be
inside the stopband
the Q of a peak refers to
the steepness of the slope
EQ TYPES
- selectable frequency EQ
- parametric EQ
- graphic EQ
- notch filter
selectable frequency EQ has a _______ of frequencies to choose from
set number
where are selectable frequency EQs typically found?
older consoles + outboard gear
parametric EQ’s center frequency is ________ _______ and the Q is also ________ _______.
continuously variable, continuously variable.
describe a graphic EQ
boost or cut level control over a series of frequencies that are spaced according to musical intervals. controls are generally liner slider types, arranged side-by-side. this type of EQ is often used in the fine-tuning of a system to match the acoustics of a room.
notch filter… why do we use it?
to remove hum and other undesirable discreet frequency noises.
notch filters have a _______ bandwidth
narrow
noise gate
allows signal that is above the threshold to pass through. once input signal falls below the threshold, the gate shuts down the signal
expander
like a noise gate, but with partial attenuation instead of full
noise gate Threshold
sets the level at which the gate will open and allows signal at the input to pass through to the output.
noise gate Range (aka Ratio or Depth)
the amount of attenuation applied to the input signal once it falls below the threshold level.
noise gate Hold
sets the amount of time the gate remains open, once the input signal falls below the threshold level.
Dynamic mics and Ribbon mics use
electro-magnetic induction
Condenser mics use
electro-static principle
tube mics have
their own power supply
two types of Analog Filter Circuits
Passive filter EQ, Active filter EQ
Passive Filter EQs consist of 3 main electrical components:
Capacitors, Resistors, Inductors
Active Filter EQ’s make use of devices called ________ which require a dedicated power source.
Differential Operational Amplifiers (OP amps)
Condenser microphones, generally:
- have a flatter frequency response
- have a faster transient response
- have a louder output level (less risk of needing to crank up mic-pre’s, which raises up the noise floor)
Dynamic microphones, generally:
- can handle more SPL
- are more durable
- are more affordable
Side-chain Input or Key Input:
a key input or side-chain input is the same thing. It’s an auxiliary input that can trigger the voltage detector (threshold) from a remote source.
Full attenuation =
Noise Gate
Partial attenuation
Expander
