Dynamic Processors & EQs Flashcards
Gate/expander
Allows the signal that is above the selected threshold to pass through to the output at unity gain and without dynamic processing
Gates threshold (trigger)
Sets the level at which the gate will open and allow signal at the input to pass through through to the output
Gate parameters
Set the level amount and if the waveform passes above it, it allows it in, and if it’s below it, it attenuates it
When a signal opens the gate, what sounds come through?
Everything
What does gating help with?
Helps remove unwanted signals
Why is gating “irrelevant” in digital audio?
Because you can just cut out areas that have bleed
What is gating typically used for in digital audio?
Creative uses
Gate: Attack
Sets how fast the fate fully opens once the signal crosses the threshold
Gate: Hold
Set the amount of time the fate remains open once the input falls below the threshold
Gate: Release
Sets the amount of time it takes the gate to close, once the input falls below the threshold level AND the hold function has expired
What do the gate functions match? (attack, etc)
Envelopes of waveforms
Attenuation (Range, depth)
The amount of attenuation applied to the input signal once it falls below the threshold
What happens if range is set at around -60dB?
It’s essentially more like a mute button, and having it mute on and off causes the instrument coming through to sound fake and unnatural
When is a bit of ‘bleed’ okay?
It’s okay to let some bleed in and let it attenuate smoothly rather than shutting the gate off quickly and causing the sound to be unnatural
Noise gate attenuation amount
Full attenuation
Expander attenuation amount
Partial attenuation
Where is an example that gating is necessary?
Live sound (used all the time) and analog editing (for those who actually do that still lol)
Compressor/limiter
A device that puts gain reduction to manipulate or control the dynamic range of an audio signal
Compressor threshold
When the input signal exceeds a pre-determined level, the compressor’s gain is reduced and the signal is attenuated
Gates vs Compressor thresholds
Gates attenuate signal when dB is BELOW the threshold, until dB goes ABOVE and the gate opens to let signal through, aka. doesn’t let softer sounds in
Compressors leave signal as is when dB is BELOW the threshold, until dB goes ABOVE and then it is attenuated, aka. doesn’t let loud sounds out
Signal path in a dynamic processor
Signal is split between two paths: audio and side-chain
Side-chain
Where the signal level is measured by a voltage detector (threshold)
Ratio
The amount of input dBs ABOVE the threshold, versus the amount of output dBs ABOVE the threshold
What you put in versus what you get back
Unity gain
1:1 ratio
4:1 compression becomes more like _____
A limiter
Compressor vs Limiter
Primary difference is the RATIO. Generally, the higher the ratio, it is more of a limiter, while a lower ratio is compressor
Gain reduction
Threshold + ratio will result in gain reduction
Compressor: Attack
The amount of time it takes for the compressor’s gain to be reduced once the signal crosses the threshold
Compressor: Release
The amount of time it takes for the compressor’s gain to return to its original level
Release side effects
If the release is too fast: pumping or breathing - a rapid rise in noise floor due to too fast of a release time for the program material
If the release is too slow: over-compression (the compressor never lets up)
Output/make-up gain
Compensates for gain reduction that occurs post-compression, that makes the compressed signal louder (match it to the input signal level)
What also gets louder when you turn up output gain?
Noise floor turns up with it - this rarely poses an issue when the whole mix is playing together as it will be masked
4 steps to setting up any compressor
- Input - insert patch
- Set ratio
- Lower the threshold to achieve gain reduction
- Match output gain to input level
Audio Equalisation
Device that enables the engineer to exercise control over the harmonic/timbral content of a live or recorded sound
Timbre
Term that describes characteristics of sound outside of pitch and volume. It is the harmonic and musical content of a sound that differentiates itself from another sound producing the same pitch, regardless of volume.
What does not have any timbre?
Sine waves (simple and pure tone)
Reasons to EQ
To correct or improve specific problems in a “live” signal, a recording, or within a room
Consumer audio EQ examples
Home stereos, car audio, record players
RIAA equalisation curve
This curve is what record players use to cut highs and boost lows at the phono preamp stage, creating a flat frequency response when being brought to speaker level
Live sound EQ examples
Feedback correction in monitorland, tune PA to the room, make the mix sound good for FOH, crossover in speakers is also a form of EQ
EQ audio in a recording setting (microphones)
EQing can help overcome deficiencies in the frequency response of a microphone or in the sound of an instrument
Not everyone will have an array of microphone/instrument selections, so EQing the equipment you do have is far more affordable
EQ audio in a recording setting (experimentation)
EQing while mixing for musical/creative reasons
This was trailblazed by the Beatles
Why is experimentation with EQing in the studio more difficult to do these days compared to when the Beatles were making music?
Because in that era, there was more money in the music industry to play around and experiment. That is not the case these days to spend money to ‘play around’ in the studio. Nowadays, the faster it’s done, the better = less money spent
EQ audio in a mixing setting
EQing sounds of different instruments that produce similar frequencies can help the tracks blend together while still being able to differentiate the instruments. Blended mix vs blurry, muddy mix
“It doesn’t matter who something sounds on its own -
it’s all about how it sounds in the mix”
Example of why we might EQ a kick drum and a bass guitar
Kick drum and bass guitar usually share common frequencies, which can cause cancellation, or muddy mix due to the frequencies competing
EQ audio in a mixing setting (leakage)
If a hi-hat is leaking into the kick drum track, or vice versa, for example, EQing helps eliminate leakage. You can use rolloffs on the mic.
Peaking curve
The most common EQ curve - peak-shaped bell curve that can be boosted / cut at a selected frequency
Q
Q is the ratio of center frequency to bandwidth; if you raise the Q, the bandwidth narrows, and if you lower the Q, the bandwidth broadens
High Q
Narrow bandwidth = less frequencies outside the selected bandwidth are being affected
Low Q
Broad bandwidth = many frequencies outside the selected Q are being affected
Shelving curve
Rise or drop in frequency response at a selected frequency, which tapers off to a preset level and continues at this level to the end of the audio spectrum
Shelving curve Q or Slew Rate
Controls the progression of amplification or attenuation from the “flat” position
Normally has a Q of 1
High/Low pass filters
Certain frequencies are passed at full level, while others are attenuated
Passband
Frequencies attenuated less than 3 dB are said to be inside the passband
Stopband
Frequencies attenuated more than 3 dB are said to be inside the stopband
Slope
The rate at which the frequencies are rolled off
High/low pass filters vs Shelving curves
High/low pass filters’ attenuation does not level off outside the passband, rather it continue to increase
Low pass filters
Low frequencies are passed, highs are rolled off
Not often found on recording consoles
Used often in post-production for effect
High pass filters
High frequencies are passed, lows are rolled off
Found on microphones and recording consoles to correct/eliminate “rumble”
Band pass filters
High pass filter and low pass filter used in combination
Used often in post-production
4 EQ types
- Selectable frequency EQ
- Parametric EQ
- Graphic EQ
- Notch filter
The first instance of audio EQing
Telephone - filtering out frequencies so that the voice can travel through wires more adequately
Selectable frequency EQ
Set number of frequencies to choose from that usually allows a boost or cut with a predetermined Q
Independent LOW, MID, and HIGH ranges
Typically found on older consoles and outboard gear
Usually has 2, 3, or 4 bands
Parametric EQ
Introduced by George Massenburg in 1971
Four overlapping frequency bands (low, low mid, high mid, high)
Centre frequency in each band is continuously variable
Amount of cut or boost is continuously variable
Q is continuously variable
Difference between parametric EQ and semi-parametric EQ
Semi-parametric has no Q or bandwidth control - the Q is only switchable between high and low
Does the Neotek Elite feature parametric EQs or Semi-parametric EQs?
Semi-parametric
Graphic EQ
Boost or cut control over a series of frequencies that are spaced according to musical intervals
Often used to tune a system to match the acoustics of a room
31 band for live sound
Graphic EQ name explanation
The controls are typically linear slider types arranged in a row side-by-side, giving a “graphic” representation of the EQ curve
Notch filter
Very little bandwidth (9 frequencies), with little effect on the rest of the material
ONLY USED to ATTENUATE a specific frequency
Notch filter attenuation in dB
Can attenuate up to -60 dB
What are notch filters used for?
Typically used to remove hum and other undesirable discreet frequency noises
ex. air conditioners, etc.
Knee of compressor
How strictly the threshold is applied/enforced
Soft knee
Lest strict enforcement of the threshold; the ratio is applied within a region surrounding the threshold and increases above the threshold
Term for soft knee on the DBX compressor
Overeasy
Hard knee
Strict enforcement of the threshold; the ratio is applied as soon as the signal crosses the threshold level
Which knee type would you use when wanting to avoid clipping?
Hard knee - with a 1:1 ratio and fast attack
Frequency dependent dynamic processing
By applying high pass and low pas filters to the side-chain, you can accomplish more frequency specific dynamic processing
ex. de-esser
De-esser
Doesn’t remove frequencies from the vocals - it removes frequencies from the side-chain
Single band compressor
Frequency dependent side-processing
You’re processing the side-chain, NOT the audio
Side-chains are called as such on compressors. What are they called on gates?
Key inputs
Key inputs
Auxiliary input that can trigger the voltage detector (threshold) from an external source
Turnover
On a high/low pass filter, the frequency at which the signal is attenuated by exactly 3 dB
Band-pass filter
When a high pass and low pass filter are used in conjunction
Frequency around which you would find the “bottom depth” of a kick drum
60 Hz
Frequency around which you would find the “attack” of a kick drum
2.5 kHz
Frequency around which you would find the “fatness” of a snare drum
240 Hz
Frequency around which you would find the “crispness” of a snare drum
5 kHz
Frequency around which you would find the “pluck” of a bass guitar
2 kHz
Frequency around which you would find the “bite” of an electric guitar
2.5 kHz
Frequency around which you would find the “shrillness” of horns
5 kHz
Frequency around which you would find the “shimmer” of cymbals
7.5 kHz
Frequency around which you would find the “presence” of a vocal
5 kHz
Frequency around which you would find the “sibilance” in a vocal
7.5 kHz
