Spectral Processors Flashcards

(44 cards)

1
Q

What are the three types of spectral processors?

A
  • Filters
  • equalizers
  • aural exciters
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2
Q

What are the 6 types of filters?

A
  • LPF (low pass filter)
  • HPF (high pass filter)
  • band-pass filter
  • band-reject filter
  • notch filter
  • all-pass filter
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3
Q

In a low-pass filter, what is the cutoff frequency?

A

frequency where the output is -3.01 dB

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4
Q

In a low-pass filter, what is the slope?

A

dB per octave attenuation (below cutoff frequency)

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5
Q

In a low-pass filter, what is the order?

A

-first order is 6.02 dB/oct, second is 2x6.02 dB/oct -also called poles

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6
Q

What is a high-pass filter?

A
  • allows high frequencies below a certain frequency to pass through
  • slopes up from left to right
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7
Q

What is a low-pass filter?

A
  • allows low frequencies below a certain frequency to pass through
  • slopes down from left to right
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8
Q

Why is cutoff frequency defined at -3dB?

A
  • electrical engineers define 3dB as doubling of power
  • slope becomes mostly linear after this point
  • it is the point at which the effect is clearly audible
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9
Q

What are band-pass filters?

A

-high-pass filters and low-pass filters together

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10
Q

In a band-pass filter, what is the equation for bandwidth?

A

difference between two cutoff frequencies

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11
Q

In a band-pass filter, what is the equation for cutoff frequency?

A

cf=√(cf1*cf2)

ex. cf1=220, cf2=880

cf=√220*880

cf=√193600

cf=440

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12
Q

What is a band-reject filter?

A

reduces gain at a particular frequency

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13
Q

What is a notch filter?

A

band-reject filter with extreme attenuation at a single frequency and a very narrow bandwidth

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14
Q

What is an all-pass filter?

A
  • passes all frequencies equally, without attenuation
  • changes the phase relationship between frequencies
  • described by the frequency where the phase shift crosses 90° (¼ wavelength delay)
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15
Q

How is a phase shift achieved in an all-pass filter?

A

varying the filter’s propagation delay by frequency

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16
Q

What are all-pass filters used for (3 things)?

A
  • compensate for unwanted phase shifts
  • create intentional comb filter effects
  • multiple are used for a phase shifter
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17
Q

How do equalizers differ from filters (5 ways)?

A
  • EQs are made of a collection of filters (bands)
  • EQs allow control over the gain of the filter
  • EQs can boost and attenuate
  • EQs leave the gain of frequencies outside of the band-pass/band-reject filter at zero dB
  • bandwidth is measured 3dB below the peak of the curve
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18
Q

What is a peaking equalizer?

A

a band-pass filter that leaves the gain of the frequencies outisde of it at zero dB

19
Q

How does an asymmetrical filter work?

A

bandwidth is measured 3dB below zero on the cutting side and 3dB below peak on boosting side

20
Q

How does a symmetrical filter work?

A

bandwidth is measured 3dB above zero for boosting and 3dB below zero for cutting

21
Q

What is a constant range (proportional Q) EQ?

A

Q narrows as boost or cut increases

22
Q

What is a constant Q EQ?

A

Q remains constant as boost or cut increases

23
Q

In an EQ, which frequency controls are peaking filters?

A

mid frequencies

24
Q

What is a shelving equalizer?

A

-allows for boost or cut of frequencies above or below a given frequency

25
In an EQ, which frequency controls are shelving filters?
high and low frequencies
26
What are the two critical frequencies in a shelving EQ?
- stop frequency - turnover frequency
27
What is the equation for transition ratio on a shelving EQ?
transition ratio=stop freq/turnover freq
28
In a shelving EQ, what is overshoot?
boost of frequencies just above (low shelf) or below (high shelf) the cut
29
In a shelving EQ, what is undershoot?
attenuation of frequencies just above (low shelf) or below (high shelf) the boost in a shelving EQ
30
What are 5 things to consider about phase response in filters?
- not all frequencies pass through equally - EQs may shift the phase of a certain frequency - each frequency range or octave may have a different phase response than the others - phase response may be different at different Q settings - phase shift can give character
31
What are the four types of equalizers?
- parametric - graphic - paragraphic - semi parametric
32
What are 4 characteristics of a parametric equalizer?
- full control over center frequency, boost/cut, and Q - all bands independent - high and low bands typically provide peaking and shelving modes - typically bands are in series
33
What are 3 characteristics of a graphic equalizer?
- fixed frequency sliders - one third, two third, or octave bandwidths - typically bands are in parallel
34
What are the characteristics of a paragraphic equalizer?
- graphic EQ with fine tuning of bands - digital parametric EQ with graphic display
35
What are 2 characteristics of a semi parametric equalizer?
- may not have full control over all bands - all bands may not be independent
36
What are 3 typical uses for EQ?
- spectral balance - timbral correction - tonal enhancement
37
What are the typical uses for a high-pass filter?
remove unwanted frequency content such as room rumble
38
What are the typical uses for a low-pass filter?
remove unwanted frequency content such as fret squeaks on a bass guitar
39
What is the main use for a band-pass filter?
telephone voice
40
What are 3 main uses for a band-reject or notch filter?
- even out the notes on a bass guitar - reduce problem resonant frequencies - reduce sibilance on a vocal
41
What is the main use for a shelving equalizer?
high or low frequency enhancement, resoration, or attenuation
42
What are high-pass filters useful for?
-useful to remove room rumble and some mechanical noises
43
In a shelving EQ, what is stop frequency?
the frequency 3dB above or below where the curve levels off
44
In a shelving EQ, what is turnover frequency?
the frequency 3db above or below flat, when the slope becomes linear