AUdIoCoUrSeS
Joined: 31 Oct 2002
Posts: 2014
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| Week 4 - Questions |
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1. What is the function of mixing desk automation?
2. Why might the faders have to be moved during the mix?
3. What aspects of mixing would normally be automated on an analogue console?
4. Comment on VCA vs. Moving Fader automation.
5. Describe write/update/read.
6. How does an automated mix session start?
7. How would a section of automation data be re-recorded?
8. How are automation 'punch-ins' blended smoothly with existing data?
9. How could a complex series of moves be increased in level by say 3dB?
10. Describe fader grouping.
11. How could EQ, for instance, be automated using an analogue mixing console?
12. How would EQ be automated using a digital mixing console?
13. What is 'recall'?
14. What advantages does a digital console have over an analogue console regarding recall?
15. Does a compressor act upon loud signals or quiet signals? What does it do to the signals upon which it acts?
18. What is the function of 'make up gain'?
19. How is a compressor usually connected to a mixing console to compress a single signal?
20. How is a compressor connected to a mixing console to compress the entire mix?
21. Explain 'ratio', in the context of compression.
22. Describe the difference between hard knee and soft knee.
23. What are 'breathing' and 'pumping'?
24. What happens if the release time is too long?
25. What does it mean if the gain reduction meter is showing frequent changes?
26. Describe the effect of compression on noise level.
27. Describe the function of the stereo link switch.
28. What is the side chain input?
29. Describe a typical use of the side chain input.
30. Is a noise gate usually effective on a mixed stereo signal?
31. Is a noise gate effective on a signal where the instrument plays all the time?
32. Is a noise gate effective on a single noisy signal where there gaps in the playing?
33. Why is it often considered beneficial to gate some or all of the mics on a drum kit (except the overheads)?
34. How many gates are often used in live sound: none, a few or many?
35. How is the noise gate connected to the mixing console?
36. What is the function of the Threshold control?
37. What is the function of the Range control?
38. Comment on the Attack, Hold and Release (Decay) controls.
39. What would happen if a stereo signal was gated, but the stereo link function was not selected?
40. Why are side-chain filters beneficial?
41. Comment on the use of an external key to improve the reliability of gating.
42. What is an expander?
43. Why are compressors and gates often used together?
44. Comment on envelope shaping using a noise gate.
45. Comment on gated reverb.
_________________
It's all in the ears. - Learn the concepts not the software.
Audio Courses is a way into the music business for you
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Mon Mar 28, 2005 6:07 am |
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hoaxwagon
Joined: 28 Feb 2005
Posts: 27
Location: Boulder Creek, CA USA |
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DD, hoaxwagons RT wk 4 Q&A 
1. What is the function of mixing desk automation?
Mixing desk automation is able to recall stored effects settings and patch configurations. This
automation can be asked to perform numerous settings changes simultaneously or a modest one
adjustment at a time. The automation can be used if the sound of a band changes often. For example
bands like YES who often shoot for sounding like their studio recordings would benefit from
automation. With the use of snap shots, automation will also come to the aid of a touring bands sound
engineers when it remembers the particular settings on the desk and other out board processors for that
room from the last time they were there ( recall ). These parameters can be programmed off line, days
before the sound system is even hooked up. In the studio with mute automation, all your mutes and
unmutes will be logged in MTC and play back at exactly the right times. This is a way to clean up
tracks. Having the channel muted until is needed will cut out any unwanted sounds that inevidably sneak
into a mix on the silent parts of a track. [R]1 [R]2
[R]1 http://www.record-producer.com/learn/automated-mixing-part-3.html
[R]2 http://www.svconline.com/mag/avinstall_computer_automation_soundreinforcement/
2. Why might the faders have to be moved during the mix?
The faders might need to be moved during a mix if the level of the signal associated with that particular
fader needs to be adjusted.
3. What aspects of mixing would normally be automated on an analogue console?
In some cases automation can be added to an existing console as a retrofit. Adding automation nearly
always involves taking the console apart and rewiring, or even replacing, the faders.
http://www.record-producer.com/learn/automated-mixing-part-6.html
The aspects of mixing that are normally automated on this type of analogue console are the fader
controls and the channel mutes.
I suppose there are even more aspects of mixing that would normally be automated on an analogue
console if Solid State Logics SL 9000 J analogue mixing console with advanced automation and computer
control facilities is what your on. [R]http://www.recordproduction.com/recording-equipment.html
Also while on an analogue mixing console a sync signal can be used to automate midi devices with a
multitrack recorder, midi interface and a computer running sequencing software .[R]
http://www.alesis.com/support/cc/sync.html
4. Comment on VCA vs. Moving Fader automation.
Moving fader systems employ the physical moving of faders. A VCA or "voltage controlled amplifier" is
a system in which the faders movements are stored on the computer and represented by images on a
computer monitor. Its about personal taste and needs issues when it comes choosing which system to
use. [R]http://www.jeepjazz.com/handbk.html#Automation
5. Describe write/update/read.
The write mode is the state in which a mixing console can be put in to record one or a series of
movements for automatic recall later. The update is a mode to be in when a cue that has already been
written needs to be updated or changed. The console is in read mode when it is implementing cues that
have been set up earlier.
6. How does an automated mix session start?
An automated mix session starts by recording a short section of automation (or use the Write
Automation command) across all faders and plug-ins at the start of the song before starting an
automated mix session. This anchors absolutely everything from the start.
[R]http://www.soundonsound.com/sos/Jun03/articles/pronotes0603.asp
7. How would a section of automation data be re-recorded?
During playback , use write mode and make the desired adjustments then use the update mode to save
the changes. Using the Snap button you can record all the current fader and mute settings, pan positions,
auxiliary buss settings and effect sends and returns.
8. How are automation 'punch-ins' blended smoothly with existing data?
The channel that the punch in is on can be faded in at the start and faded out at the end for a seamless
effect
9. How could a complex series of moves be increased in level by say 3dB?
Put the console into manual or auto take over mode, then the faders involved can be grouped to a
master fader and then the level of this master fader can be brought up 3 decibels. If the auto write was
used the console should have automatically recorded the changes desired. If manual mode is used then
the update function can be used to store the changes.
10. Describe fader grouping.
Fader grouping is used when two or more channels are assigned to a fader that controls the sounds as a
combination of the individual tracks. I’ve seen these called sub groups. For example, once the proper
mix has been achieved on a 5 piece horn section and assigned to a master fader, the level of the sounds
can be adjusted with the one fader. Drum mic levels can also be set and the channels assigned to a
master fader.
11. How could EQ, for instance, be automated using an analogue mixing console?
An EQ that is interfaced with a computer that can store the different settings to be manually
implemented or automatically implemented by use data information placed on one or two of the tracks.
12. How would EQ be automated using a digital mixing console?
Snap shots of the EQ settings for each particular change can be recorded as cues. Through the use of
the read mode the cues can be implemented automatically.
13. What is 'recall'?
On Total automated consoles total recall enables instant access to saved settings configurations, cues,
that were stored through the use of snap shots.
It is a means for referencing a display that shows the preferred settings previously stored. This just a
reference. The controls have to be adjusted manually.
14. What advantages does a digital console have over an analogue console regarding recall?
The advantages of a digital consoles recall are endless. The digital console and its recall abilities make it
possible for the consistent and reliable mix to be a given. Lets face it, an engineer on an analogue
console can write down settings, mark channels with tape for reference and stay busy all the time by
making the necessary adjustments needed for a complicated mix or he/she can use the automated
features of a digital console to ensure a more efficient set up. In the studio, the engineer is usually
requested by the producer to make certain adjustments at certain times. These requests can start adding
up and before you know it there is no way to comply with, or even remember the many changes
requested. Automation can assist by documenting each individual request as it come up until the
requests are all fulfilled. All this hard work can be recalled years later.
15. Does a compressor act upon loud signals or quiet signals? What does it do to the signals upon
which it acts?
The compressor responds to the louder signals and knocks down the dynamic peaks. With all the
settings just so, the impression can be that the compressor works on the quite sounds by boosting them
but in reality the loud sounds are brought down to a level more consistent with softer sounds giving the
impression of boosted softer signals when the whole mix is turned up.
18. What is the function of 'make up gain'?
The make up gains function is restore the decibels that are lost by compressing or limiting. The make up
gains volume level control knob on the compressor/limiter would be used. On some hardware this
control knob is called output.
19. How is a compressor usually connected to a mixing console to compress a single signal?
If a single signal on a mixing console is in need of a compressor it can be hooked up to an auxiliary send
and return on the aux buss and controlled by the aux bus levels. It can be fed by the aux out and then
sent to another channel input for artistic effect and controlled by the send on the aux bus and the
controls on the return channel. It can be patched into the individual channel patch. This is sometimes
done using a 1/4 inch stereo, ring tip sleeve plug that Y’s to two 1/4 inch jacks that are the send and
return for the channel patch.
20. How is a compressor connected to a mixing console to compress the entire mix?
A compressor can be connected to the auxillary buss, lets say ‘aux 1 send’ to the input of the
compressor and the output of the compressor to ‘aux 1 return’. With this in place, the aux 1 control
knob found on each channel can send the channels signals to the compressor.
21. Explain 'ratio', in the context of compression.
When the gain reduction meter is showing minus 3 decibels and the ratio is set for 2:1, the actual
amount of gain reduction is 6 decibels. Ratio is the difference between what the gains reduction meter is
displaying and the actual amount of gain reduction taking place.
22. Describe the difference between hard knee and soft knee.
Hard knee compression is when the compressor delivers, to the signal over threshold, the ratio that is
requested. Soft knee compression is when the ratio is gradually increased from 1:1 to the actual ratio
set on the ratio control. The transition from compressed to uncompressed is more gradual.
23. What are 'breathing' and 'pumping'?
Breathing and pumping are terms given to the sound a compressor makes when it is set to make an
unnatural amount of cut and is set to release to fast. The LED’s on the compressor displaying the
amount of signal there is above the threshold will also pump up and down to give you a visual of the
effect. Slowing down the attack and release ought to fix this a bit. (audible compression due to rapid
gain changes) Pumping or breathing is when there is a audible raising and lowering of the noise floor.
24. What happens if the release time is too long?
If the release time is to long more than just the transients will be compressed. That is if the idea is for
the compressor to react to the louder signals when they happen but to return to threshold before a signal
comes along that doesn’t need to be compressed. A slow release time can be a desired setting when a
guitar or a vocal needs sustain.
25. What does it mean if the gain reduction meter is showing frequent changes?
It could mean that the threshold or ‘gain’ control is set low enough, allowing the signal level to come
over the threshold , and a release time set somewhat fast or ‘short’ is rushing the signal back to
threshold. If the idea is to compress a signal, a gain reduction meter that shows frequent changes might
suggest that intended compression is taking place or it could mean that the compressor is ‘breathing‘ or
‘pumping’. This may be not so good.
26. Describe the effect of compression on noise level.
A compressor can be set up in such a way that most of the signal is over the threshold most of the time.
This set up will produce some gain reduction. How much would depend on the ratio setting. The signal
is now quieter so the make up gain can be used to turn the level back up. The noise floor is raised right
along with it. This is indicative to the very concept of compression.
27. Describe the function of the stereo link switch.
Its function is to allow for two or more compressors to be used together to provide accurate
stereo compression or limiting. When compressors are linked like this, the one that is getting to and over
threshold soonest is the one that the other(s) mimic. The gain reduction meter on each device still
reflects the settings of their respective devices.
28. What is the side chain input?
A side chain input or ‘detector patch’ return is a connection on a compressor used for the insertion of
a vocal mic for ducking or an EQ for de-essing and de-popping
29. Describe a typical use of the side chain input.
When a music signal is being sent through a compressor and a vocal is attached to the side chain input,
the compressor/limiter uses the vocal in the side chain to control the amount of compression on the
music. The result is that when the person is talking, the level of the music is lowered and when the
person isn’t talking the level of the music is returned.
30. Is a noise gate usually effective on a mixed stereo signal?
If the mixed stereo signal is a combination of sounds that are always playing, I cant see a use for a noise
gate.
31. Is a noise gate effective on a signal where the instrument plays all the time?
I don’t think the gate would be doing its job if it were always open. Which is what would be the case if
it were used on a signal with a constant level. If there silence between the notes that are being played all
the time then a noise gate could come in handy for silencing the dead space.
32. Is a noise gate effective on a single noisy signal where there gaps in the playing?
Yes, this is what it is used for
33. Why is it often considered beneficial to gate some or all of the mics on a drum kit (except the
overheads)?
It is often that gates are used on the drum set mics to minimize spill or leakage. The mics on a set are
close enough together and would constantly be picking up each others intended signals otherwise.
34. How many gates are often used in live sound: none, a few or many?
Many gates are used unless there is a digital console with mute automation which is equivalent to the
application of a gate used for the same purpose.
35. How is the noise gate connected to the mixing console?
A noise gate would probably be connected to the console via the channel patch.
36. What is the function of the Threshold control?
The threshold control is adjusted to find the point in which a desired signals presence opens the gate and
its absence allows the gate to close. [R] SOS
37. What is the function of the Range control?
The range controls function is to adjust the amount of attenuation given to signals below the threshold.
Maximum attenuation is what a gate automatically provides but for a less noticeable gate operation and
for a more natural sound adjust this control so that the gate doesn’t completely close.
38. Comment on the Attack, Hold and Release (Decay) controls.
The hold control sets the amount of time the gate will stay fully open even though a signal has dropped
below threshold. The hold might want to be set above zero to avoid jitter. ( the state when the gate is
trying to open and close at the same time) Attack controls the speed in which the gate opens in
response to a sound over threshold and the release controls the speed in which the gate closes once a
signal drops below threshold.
39. What would happen if a stereo signal was gated, but the stereo link function was not selected?
The two gates would respond to their respective channels independently and open and close at slightly
different times.
40. Why are side-chain filters beneficial?
They are ideal for de-essing or de-popping a troubling frequency.
Side chain filters are used to dial out frequencies inherent in another sound source that are making it
impossible for the gate to be triggered accurately by its intended sound source.
41. Comment on the use of an external key to improve the reliability of gating.
The external key is an input on the gate with a corresponding switch. This input can be used for a
contact mic, which has just the intended sound, to trigger the gate open a split second sooner than the
regular mic is able. This ensures that the gate is open in time and that the transient of the signal from the
regular mic is preserved.
42. What is an expander?
An expander is a devise that is used to amplify signals that are below threshold therefor extending the
dynamic range of a signal. When a signal is above threshold there is no difference in level but when a
signal falls below threshold the signal is boosted.
43. Why are compressors and gates often used together?
An upward compressor , when in gain reduction mode, introduces some noise because the noise floor
has been raised . A noise gate can be set up to close before the sound of the noise floor becomes most
obvious, during the absence of the desired signal. They are used together to perform complimentary but
totally different tasks.
44. Comment on envelope shaping using a noise gate.
The dynamic envelope (amplitude) of any sound connected to the external key can be imposed onto any
audio signal passing through the gate. The attack, hold and release are all used to achieve the desired
envelope.
45. Comment on gated reverb.
Gated reverb is the reverb on a signal that is being gated. The idea is to have the gate close before the
reverb tail has finished. A noise gate can be inserted into the channel patch of a reverb return channel
for a particular source channel. The output from the sources channel patch can be fed into the side chain
of the reverb channels gate so the gate is open only while the source is sounding. |
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Sat Apr 02, 2005 11:43 am |
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chemira
Joined: 03 Jan 2005
Posts: 50
Location: Nova Scotia Canada Eh! |
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Recording Techniques Week 4
1. What is the function of mixing desk automation?
Mixing automation can assist the mixing engineer with repeated tasks, multiply tasks or tasks that are too complex for one or several engineers to navigate successfully. Mixer automation can allow the precise muting of tracks fade ins and outs with repeated accuracy that an engineer or several could not do. Track counts number in the dozens so there would be too many tracks to deal with. [1]
2. Why might the faders have to be moved during the mix?
Faders may need to be moved during a mix to allow volume increase or decrease to add focus to a certain instrument, voice or a section. Bringing in certain elements of the mix can add a more interesting mix likewise lowering or removing an instrument can change the focus to another instrument, voice or section. [1]
3. What aspects of mixing would normally be automated on an analogue console?
Mutes, fade ins fadeouts panning and fader groupings are usually what would be automated on an analogue console.
4. Comment on VCA vs. Moving Fader automation.
A recording console that is controlled by VCA automation can control the track volume with reference to a pre set level which the VCA controls. The faders in a VCA based console do not move but a visual movement on a computer screen represents the movement of the tracks fader. Moving faders are a direct visual movement of the fader that corresponds to the output of the fader being moved. The fader is driven by a small motor that follows the commands of a synchronized timing master so that the movements are repeatable. [2]
5. Describe write/update/read.
Write Mode is when the engineer is in control of the gain setting as the song progresses. The engineers movements will be recorded into an automation computer to save the real time movements that the engineer makes.
Update Mode allows the engineer to adjust and rewrite the automation that was made in write mode.
Read mode is when the faders move in accordance with the input fader movement that the engineer made during write mode as the song plays back. [3] [4]
6. How does an automated mix session start?
Automation write must be enabled, select auto write for the tracks that require write automation. This will allow any movements to be recorded into the automation computer after play is pressed for the song.
7. How would a section of automation data be re-recorded?
When a section of automation required adjustments the track can be placed in write mode again and the fader can be moved to the desired setting which will overwrite the original automation data.
8. How are automation 'punch-ins' blended smoothly with existing data?
The use of a cross fade from one track to another can usually cover an automation punch in.
9. How could a complex series of moves be increased in level by say 3dB?
without affecting the original fader movements the faders that require a 3dB increase in level cn be sent to a group master fader. This fader can be automated to facilitate the 3dB boost when it will be required.
10. Describe fader grouping.
Fader grouping is grouping tracks with regards to their similarities or routing requirements. A drum group, vocal backing or auxiliary percussion group can be faded in or out with the movement of one fader.
11. How could EQ, for instance, be automated using an analogue mixing console?
Depending on tracks available and mixer architecture a track can be copied to two different track where each track receives different EQ or effects. Write automation to cross fade between the two tracks. Or select a buss to do the same thing routing the track or tracks to the different sounding EQ buss.
12. How would EQ be automated using a digital mixing console?
In some digital mixing consoles the EQ can be automated and recorded as automation recall data. If possible the filter can be selected for automation and adjusted during write mode.
13. What is 'recall'?
Recall is a snapshot of all positions at a given time. Snapshots can be saved and recalled at any given time.
14. What advantages does a digital console have over an analogue console regarding recall?
A digital console can save more settings and more snapshots.
15. Does a compressor act upon loud signals or quiet signals? What does it do to the signals upon which it acts?
A compressor acts on loud signals that exceed a pre set threshold level. What a compressor does is react to the signal by reducing the signal by a preset ratio weather fixed or variable that is directly proportional to the setting. If the setting is 2:1 for every 2dB over the threshold the resultant output will be 1dB gain over the threshold setting. [5]
18. What is the function of 'make up gain'?
Make up gain is required when the compressed signal has be reduced due to the function of compression. The signal may be attenuated too low to be used in the mix so the signal must be increased.
19. How is a compressor usually connected to a mixing console to compress a single signal?
A compressor must be nserted into the signal path to properly affect the signal.
20. How is a compressor connected to a mixing console to compress the entire mix?
A compressor, usually a stereo linkable unit or two mono units will be “strapped” on the output mix buss. This will be the final signal output on the mixer before the signal is monitored. [5]
21. Explain 'ratio', in the context of compression.
If the setting is 2:1 on a compressor for every 2(dB units) over the threshold the resultant output will be 1dB gain over the threshold setting. So if the threshold is –10dB and the signal is at –2dBpeak the signal over the threshold is 8dBpeak. Ratio determines that for ever 2 in you get 1 out so the gain over threshold will be 4dB. Quick math gives you a peak signal of –6db instead of –2dB. Higher ratios allow less signal. Replacing 4:1 for the same peak signals the output will be –8dB. Big difference in level. 8:1 leaves a –9dB signal. [5]
22. Describe the difference between hard knee and soft knee.
Knee is a term which describes how the compressor will start to react as the signal reaches threshold. A hard knee acts right away while a soft knee compresses more gradually as th signal reaches and rises above the threshold level. [5]
23. What are 'breathing' and 'pumping'?
Breathing is the sound of a singers voice that becomes audible as the compressor recovers from compressing after the singer has stopped singing. In between the phrases the compressor will stop attenuating and the signal will go back to a no gain reduction state. This can allow the breath noise to come through.
Pumping can occur when an loud signal that was controlling a buss or mix buss compressor stops playing in the mix. After the loud signal is gone the compressor reduces the amount of gain reduction and the rest of the signal in the buss will increase in volume. [5]
24. What happens if the release time is too long?
25. What does it mean if the gain reduction meter is showing frequent changes?
When a gain reduction meter is showing frequent changes then this is an indication that the signal is being reduced.
26. Describe the effect of compression on noise level.
A compressor will as the signal is boosted using make-up gain raise the noise floor that was present in the original signal. This is a negative side effect due to the need for make up gain.
27. Describe the function of the stereo link switch.
The stereo like switch allows both the left and right signals to be controlled and compressed the same amount utilizing one set of controls, usually the left.
28. What is the side chain input?
A side chain input allows control of the compressor by an external signal .
29. Describe a typical use of the side chain input.
A side chain can be used for de-essing the output signal of a vocal track by sending the sibilant frequencies boosted to the side-chain. This will make the compressor react as soon as the boosted sibilant frequencies are apparent.[6]
30. Is a noise gate usually effective on a mixed stereo signal?
A noise gat is not effective on a mixed stereo signal. It would only be effective at the beginning of a mixed stereo signal.
31. Is a noise gate effective on a signal where the instrument plays all the time?
A noise gate is typically used on signals that stop and start repeatedly.
32. Is a noise gate effective on a single noisy signal where there gaps in the playing?
Yes a noise gate can be very effective on a signal that stops and starts so as the instrument stops the gate will turn of the output after the signal fall below the pre set threshold.
33. Why is it often considered beneficial to gate some or all of the mics on a drum kit (except the overheads)?
This will stop the recording of unwanted instrument bleed from other mics on the drum kit. The overheads should not be gated to keep the overall sound of the drum kit present which can most often hide the gating process of the other instruments in the mix.
34. How many gates are often used in live sound: none, a few or many?
In essence all instruments could be gated in a live setup but with resources limited drums like kick snare and toms would be first on the list for gating to keep the attack of the drums tight and punchy. Other instruments such as bass and electric guitar may have their own gating in their effects. If not the gate can eliminate extra amplified noise in between songs produced by cheap or single coil pick-ups.
35. How is the noise gate connected to the mixing console?
A noise gate is placed either in an insert or prior to any other processing.
36. What is the function of the Threshold control?
The threshold is the point at which the signal will open and close the gate, turn the channel on and off.
37. What is the function of the Range control?
The range control is the level that the gate will attenuate the signal when the gate is closed. [6]
38. Comment on the Attack, Hold and Release (Decay) controls.
Attack control regarding a gate is the time that the gate will take to open after the threshold signal is reached.
Hold is the time that the gate will stay open after the signal had decayed below the threshold.
Decay is the amount of time the gate will take to close to its full attenuation. [6]
39. What would happen if a stereo signal was gated, but the stereo link function was not selected?
If the stereo signal was gated without the stereo link selected the signals would independently gate responding to left and right channels signal strength instead of uniformly.
40. Why are side-chain filters beneficial?
A side chain filter can reduce the action of a gate as it filters out frequencies that may open the gate but are not part of the tracks intended focus. An example would be low frequency content from a kick drum or snare that can open the gate for a hihats channel. A highpass filter to filter out the low frequencies may help control this gate more form the intended channel source than the bleed from other drums.
41. Comment on the use of an external key to improve the reliability of gating.
The use of keyed gating can be a benefit in a vocal backing group that has poor timing. Using the best timed vocal track to key the other tracks will improve the backing vocals performance if all the tracks are keyed from the best timed track. [8]
42. What is an expander?
An expander is used to create more volume difference from the lowest signal of a track to the highest signal in a track. This will in essence make the high signal seem higher and the low signal seem lower. This can be helpful on a track that has been heavily compressed and still has peaks for the expander to trigger from. quote “EXPANDER: A devise designed to decrease the level of low level signals and increase the level of high level signals, thus increasing the dynamic range of the signal. “ Unquote this is functionally opposite to a compressor utilizing the same functional controls of threshold, attack, ratio and relese. [9] [10]
43. Why are compressors and gates often used together?
A compressor and gate are usually used together to create a lower perceived noise from the signal that is recorded. The gate opens first for a drum hit then it is compressed, thereby not allowing the noise in between drum kits to come through and as the hit does open the gate the compressor brings up this signal. Gates can also filter out unwanted trigger signals so the gate will only open when the drum tracks focal instrument is hit. [9]
44. Comment on envelope shaping using a noise gate.
A gate can be used to dramatic effect on a signal as it passes through the gate depending on how the gate is set up. Regarding a drum a snare being the example A fast attack/ release will focus on the attack of the transient as the snare is hit. A slow attack/release will allow the body of the snare to come through slower attack can eliminate the attack hit and focus on sustain. The envelope, is what part of the sound is transmitted through the gate, attack, sustain and how long the gate stays open.
45. Comment on gated reverb.
Gated reverb can be used as an effect on drum sounds where the tail of the reverb is cut off once it drops below a certain threshold instead of allowed to decay to silence. Gated reverbs can also be used to create swells depending on the attack time and release. Reverse gated reverb is a modification on the gated reverb where the attack time is slow with a fast decay. This effect created a backwards quality to the sound due to it’s unnatural nature. [11]
[1] http://www.soundonsound.com/sos/1994_articles/aug94/mixautomation.html
[2] http://www.jeepjazz.com/handbk.html
[3] http://www.alexandermagazine.com/recordingeq/GlosPubUZ.htm
[4] http://members.aol.com/uniquenyc/key27.htm
[5] http://www.manleylabs.com/techpage/compressors_exposed.html
[6] http://www.record-producer.com/learn/compressor-side-chain.html
[7] http://www.saecollege.de/reference_material/pages/Compression.htm
[8] http://www.soundonsound.com/sos/apr01/articles/advanced.asp
[9] http://www.harmony-central.com/Effects/Articles/Expansion/
[10] http://www.soundonsound.com/information/Glossary.php
[11] http://www.soundonsound.com/sos/oct01/articles/advancedreverb1.asp
cheers |
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Sat Apr 02, 2005 12:34 pm |
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rachelh
Joined: 16 Jan 2005
Posts: 35
Location: Trinidad WI |
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1. What is the function of mixing desk automation?
Automation can be described as the storage of dynamic fader positions against time. Mixing desk automation is designed to help the engineer simplify automation when the number of simultaneously used faders is too many to handle by just one person. This is done by creating sub-areas of the mix at each pass; this gradually builds up the finished product [under computer control] making it easy for the engineer to edit. In practice, an automated system can range from able to only sense only the position of a volume fader and level-related switching functions [this is often called snapshot automation due to the representation of the mixer or console setting at only one point in time] to being a fully automated system that can store and recall all the dynamic functions of a production console. [2][3][4]
2. Why might the faders have to be moved during the mix?
During the mix, faders are moved so that the equipment will be able to cope with the dynamic range of the music. This process is known as Gain Riding. If a compressor was not used in the signal path, gain riding would have to be implemented, Gain riding in essence duplicates the action of a compressor without adding an extra device in the signal path. Also, the levels of the faders can be ‘brought up’ or increased to make quieter parts of the sound audible. [1] [2]
3. What aspects of mixing would normally be automated on an analogue console?
When dealing with the analogue console, mixing automation is usually done by converting the positions and moves of the various dynamic controls on a mixing surface [such as volume, Equalisation and Sends] into a DC voltage that can then be converted into digital data which is easily storable and allows for easy processing. This is done via the use of the VCA, DCA or a moving fader. The aspects of mixing usually automated on an analogue console would be gain, effects, routing and other analogue audio parameters, which are determined by the engineer.
4. Comment on VCA vs. Moving Fader automation.
VCA refers to a Voltage Controlled Amplifier. VCA automation is used to control the gain of a signal as a function of an external DC [direct current] control voltage, a level control or another parameter can be used to pass a scaled DC current, this is usually in the range of 0 – 5 VDC. This voltage, which is equal to the setting of the parameter, is used to vary the gain of the audio signal. Whereas the Moving Fader system, allows the fader to have two separate control paths: one to pass audio and one to pass a DC voltage. The VCA automation translates the voltage which is set by the parameter in to digital data then, on playback, this is converted back into an equivalent voltage level, which directly controls the parameter level. Whereas with the moving fader, changing the fader position will vary a control voltage which is then converted to digital data for the automation system. On playback, the control voltage is fed into a DC servo monitor in the fader which then in turn causes the fader to automatically move to the proper fader position. [4]
5. Describe write/update/read.
Write/ update/ read refers to the modes of automation. During the write mode, the mix moves are recorded into memory in real-time. Update mode allows for the already stored data can be updated and modified with only changes being recorded [update/offset mode]. Read mode refers to playback of the mixed information directly from the system’s automation computer.
6. How does an automated mix session start?
An automated mix session will begin by firstly grouping or namely creating sub-areas of the mix at each pass. This is done as a single control voltage or digital value which is used to control the relative balance of several grouped channels and/ or tracks. These sub areas are then edited during the mix down process and executed under computer control during a final mix pass. [4]
7. How would a section of automation data be re-recorded?
A section of automated data may be re-recorded via the use of the scans, which observe the various controls of a mixing surface during the course of a mix. In Write mode, the automation system will detect the associated changes and convert them in a series of corresponding digital words that can be stored directly into the computers automation memory. After the tracks are written, update mode can be used to go back at a later time to alter mix settings originally written to memory, once a control is altered or if automation is re-recorded or reversed in the input strips the updated settings can be changed by adding or subtracting from the track data rather than completely re-writing it. In this way complex moves can be obtained and remain intact while other changes are implemented. [4]
8. How are automation 'punch-ins' blended smoothly with existing data?
Automated ‘punch-ins’ are blended smoothly with existing data via update mode which can be used to go back at a later time to alter mix settings originally written to memory, once a control is altered or if automation is re-recorded or reversed in the input strips the updated settings can be changed by adding or subtracting from the track data rather than completely re-writing it. In this way complex moves can be obtained and remain intact while other changes are implemented. The data is blended smoothly due to the process of level matching which ensures that the punched in data levels correspond to the pre-existing ones, allowing for seamless transition. When using a moving fader this is automatic, for VCA this is done manually by observing the nulling indicator. [4]
9. How could a complex series of moves be increased in level by say 3dB?
A complex series of moves can be increased in level by 3dB by increasing the level fader in the input strip of the complex series by 3 dB. This is done while in update mode if the track is already written or on the individual input strip during the writing process. In update mode once a control is altered in the input strips, the updated settings can be changed by adding or subtracting from the track data rather than completely re-writing it. In this way complex moves can be obtained and remain intact while other changes are implemented. [4]
10. Describe fader grouping.
Console automation allows for faders to be easily arranged into one or more groups. Fader grouping is done via the use of a single control voltage or digital value, which is used to control the relative balance of several, grouped channels and/ or tracks. These sub areas are then edited during the mix down process and executed under computer control during a final mix pass. [4]
11. How could EQ, for instance, be automated using an analogue mixing console?
When dealing with the analogue console, mixing automation is usually done by converting the positions and moves of the various dynamic controls on a mixing surface into a DC voltage that can then be converted into digital data which is easily storable and allows for easy processing [all of which are done because analogue does not speak the digital language so conversion has to take place]. EQ can be automated using an analogue-mixing console in this way via the use of the VCA, DCA or a moving fader. [4]
12. How would EQ be automated using a digital mixing console?
Since digital consoles already speak the language for automation that is, digital, it is much easier and cost effective to code and decode gain, effects, routing and other automation functions. Translating physical controls such as equalisers into digital values, which can be understood by the mixer or console, is done via the use of VCA technology or digital controls. [4]
13. What is 'recall'?
Recall in automation describes the process by which the operator/ engineer is told the correct placement of controls, leaving it up to the user to reset the controls if desired. This term namely Total Recall was coined by SSL for its system, recall helps in saving time as the user is saved from writing down the positions of every knob and button allowing for the console to be easily reset during sessions. It is to be observed that Total Recall differs from True Total Reset as the latter allows for an interface to be positioned between the automation system and every control located on the console. [3]
14. What advantages does a digital console have over an analogue console regarding recall?
The concept of total automation resounds around the principles of an assignable mixing console. This assignable mixing console allows for ease in the implementation of storing switch closures and settings into memory [via the use of a microprocessor] therefore allowing for reiteration to be quickly done. Because a digital console inherently speaks the ‘digital language’ total recall automation is more effective than using an analogue console. With digital consoles it is much easier and cost effective to code and decode gain, effects, routing and other automation functions thus, making assigning a digital console for total automation an easy task. Analogue consoles call for converting the positions and moves of the various dynamic controls on a mixing surface [such as volume, Equalisation and Sends] into a DC voltage that can then be converted into digital data which is a longer process than that employed by a digital console. [3][4]
15. Does a compressor act upon loud signals or quiet signals? What does it do to the signals upon which it acts?
Compression acts upon loud signals by reducing their dynamic range. This done due to the inherent fact that most electrical equipment cannot deal with a large dynamic range thus clipping of the signal will occur. What compression does is it brings down the level of these exceedingly high dynamic ranges closer to the level of the low dynamic ranges in the waveform [i.e. bringing the peaks of a waveform closer to the troughs] maximum compression is when the dynamic range is removed completely; the signal is at one constant level throughout the track, usually, after compression; gain make-up is used to boost the signal. Compression is actually automatic gain riding, instead of manually moving the faders a compressor is used. Compression can be implemented after recording via a digital compression unit or, a compressor box can be placed into the insert point of a console with a threshold. [1]
18. What is the function of 'make up gain'?
The function of ‘make up gain’ is to boost the signal after compression. Essentially, gain make-up is like a volume control for the compressor. The result of this process is that the lower sounds of the signal are ousted up and brought closer to the level of the original loud parts. [1]
19. How is a compressor usually connected to a mixing console to compress a single signal?
A compressor is usually connected to the insert point of the particular signal on the mixing console. This allows for the signal in the channel to be compressed using a pre-determined threshold. Once the signal in the channel exceeds the threshold compression is initiated.
20. How is a compressor connected to a mixing console to compress the entire mix?
A compressor can be connected to a mixing console to compress the entire mix via connecting the compressor to the group insert point on the console.
21. Explain 'ratio', in the context of compression.
In compression, the term ratio determines the slope of the input-to-output gain ratio that is, it determines the increase of the input signal using the decibel scale which is used to determine a 1 dB increase at the output signal of the compressor. For example, setting the ratio to 4:1 would produce a 1 dB increase for every 4 dB increase at the input [reducing the signal by a rate of 4:1]
22. Describe the difference between hard knee and soft knee.
The point at which the slope of a compressor curve shows variation or change is known as the knee. Hard knee indicates normal and go immediately from uncompressed to compressed at the exact threshold level. Whilst soft knee or "over easy" is a low compression ratio for low-level signals and a high compression ratio for high-level signals, this characteristic sounds more natural and subtle than a constant compression ratio and blends gently. [1]
23. What are 'breathing' and 'pumping'?
When a compressor is set to instantly turn down a signal the response may be audible in the form of breathing and pumping within the signal’s dynamics. This problem can be rectified by using a slow attack setting, where attack is defined as how fast or slow the device will turn down signals that exceed the threshold namely the time it takes for the gain to decrease to a percentage of its final gain value [usually 63%] or in the case of release which is defined as the time that it takes to the device to restore a signal to its original dynamic level once it falls below the threshold point popping and pumping can be avoided by shortening the release time. [4]
24. What happens if the release time is too long?
The release time of a compressor is the time that it takes to the device to restore a signal to its original dynamic level once it falls below the threshold point [after attack occurs], it is the measure of how fast or slow this can be done and is usually at the gain level of 63%. If the release setting is set too fast, this creates a pumping sound whilst if the release time is too long it affects the dynamics through the transition from a loud to a softer passage. [4]
25. What does it mean if the gain reduction meter is showing frequent changes?
The gain reduction meter indicates when compression is occurring. When the gain meter peaks, this indicates that the signal is in its higher dynamic ranges and when it dips this indicates that the signal is in its lower dynamic ranges / a steady rate of reduction. If frequent changes are presented via the meter, this indicates that the signal passing through the channel is in the range above the threshold thus the compressor is working constantly.
26. Describe the effect of compression on noise level.
Compression reduces the noise level or dynamic range of a signal. The user can determine by how much the noise level should be reduced by setting a threshold. Graphically, compression brings the troughs and the peaks of a waveform together, thus reducing the dynamic range of the signal.
27. Describe the function of the stereo link switch.
The stereo link switch allows for a compressed signal to have the same amount of gain reduction at both channels. This switch when activated this prevents loud signals from one channel to be lowered to a level beneath the signal in the other signal whereas that signal will remain the same, thus, the stereo image of the signal is kept in tact. [4]
28. What is the side chain input?
The side chain input of a compressor allows for the signal that is passing through the compressor to be controlled by the dynamics of another separate signal. In general the amount of expansion and compression is related to the dynamics set at the input signal. [4]
29. Describe a typical use of the side chain input.
The side chain input of a compressor allows for the signal that is passing through the compressor to be controlled by the dynamics of another separate signal. In general the amount of expansion and compression is related to the dynamics set at the input signal. One compressing technique that uses the side chain is de-essing. Sibilants such as- 'sss', ‘chhh’ and ‘ffff’ sounds - which detract from the quality of a recording, can be removed via the use of a de-esser. Compression can only be used to remove sibilants when there is an excessive level of high frequencies and equalisation would only dullen the sound, thus, it is better to use a de-esser. [4]
30. Is a noise gate usually effective on a mixed stereo signal?
A noise gate cannot be used on a mix of signals such as a mixed stereo signal. It can only be used on a single unmixed single.
31. Is a noise gate effective on a signal where the instrument plays all the time?
A noise gate will only be effective if there are periods of silence thus, it will not be effective on an instrument that plays all the time. Silence is an indication that the signal level is low and the gate should be shut to disallow noise from entering.
32. Is a noise gate effective on a single noisy signal where there gaps in the playing?
The ideal environment for a noise gate is one where the signal is noisy and there are gaps in the playing. Once the gate is applied the ‘noise’ in the original signal will be eliminated, leaving behind a much clearer sound.
33. Why is it often considered beneficial to gate some or all of the mics on a drum kit (except the overheads)?
It is often considered beneficial to gate some or all of the mics on a drum kit except for the overheads because of the bleeding between the instruments. Because of the dynamic range of the instruments found on the drum kit, a mic in addition to its own instrument would pick up every instrument found in the kit itself. This produces a blurry sound that is not clear and focused. Thus, noise gates can be applied to the mics [all except the overheads] to combat this signal bleeding, the channel being set so that it can capture only when the drum is actually playing and shut [usually not completely, to allow for attenuation] after the note is executed. [4][1]
34. How many gates are often used in live sound: none, a few or many?
The number of gates that can be used in live sound is limitless, in a band; all of the instruments and microphones can be gated, especially if the sound is being recorded.
35. How is the noise gate connected to the mixing console?
A noise gate is connected to a mixing console via the channel insert point. The gates are usually located in the dynamics section of the console. [1]
36. What is the function of the Threshold control?
The threshold control of a noise gate is used to set the level at which the gate will open and close. When the signal passing through the channel is above the threshold the gate will remain open, when the level of the signal goes beneath the threshold parameter, the gate is closed. If the control is set to the minimum it will allow for all signals including noise to pass through the gate, if it is set to the maximum, it will result in the gate closing because the signal will never rise above this level. Thus, the threshold should be set at a point that will allow the signal to pass through the gate whilst eliminating noise. [4]
37. What is the function of the Range control?
The function of the Range control is that it sets the degree of attenuation [the rate of decrease of the signal] when the gate is closed. Noise gates are usually set at a high attenuation rate. If the opening and closing of a noise gate is noticeable then the range control should be adjusted to combat this - attenuation should be subtle. [4]
38. Comment on the Attack, Hold and Release (Decay) controls.
On a noise gate the attack and decay / release controls are used to manipulate the envelope of the sound. This is done so that there is a smooth, noiseless transition from silence to full signal and back again. The hold control is used to set the period of time for which the gate should remain open even though the signal has dropped beneath the threshold. This allows for smooth transition and the elimination of the unwanted awareness of when the gate is opened and shut. Jitter occurs when the gates goes from open to close a number of times because it cannot determine when it is actually supposed to perform its action, this often happens when the hold time is set to zero. The hold therefore will have to be adjusted to the minimum level that allows for jitter to be eliminated. The hysterics control found on some gates allows for a separate threshold to be set for rising signals versus falling signals. [4]
39. What would happen if a stereo signal was gated, but the stereo link function was not selected?
The stereo link function in a noise gate used for applying a twin channel gate onto a stereo signal, it is only used for this purpose. If a stereo signal was gated, but the stereo link function was not selected, the result would be that the signals wuld start at slightly different times leading to out-of-phase distorted signals. [4]
40. Why are side-chain filters beneficial?
Side chain filters are beneficial as they can control the behaviour of a processed signal. Side chain filters are especially useful when you are confronted with a situation such as when gating a drum kit where the threshold point is impossible to seamlessly fit in due to the high dynamic range of the instruments in the kit. [4]
41. Comment on the use of an external key to improve the reliability of gating.
An external key can be used to improve the reliability of gating when options such as side chain filters cannot produce the seamless transitions needed when setting a gate threshold. This is firstly done by double miking the instrument. One of the signals would be from the regular mic that you were using all along in its regular position; this is fed through a noise gate as normal. The second mic is placed near the instrument in a position that allows for the lowest incidence of signal bleeding from the surrounding instruments. This signal is fed via the use of a preamp to the external key input of the noise gate. The result is that the signal from the second mic fed into the external key will be picked up earlier than the signal that is normally gated, this allows for the gate to open up a little earlier so that the transient of the instrument is accurately captured, the result of which is the gate being triggered by a signal that picks up a minimal amount of external sound. [4]
42. What is an expander?
An expander is used to proportionally increase the dynamic range of a signal when it is below the threshold. Thus, when the signal is above the threshold, the expander remains inactive. An expander can be used as a noise reducer by adjusting the expander so that the noise id downwardly expanded during the quiet passages while louder program levels are unaffected and are only moderately reduced. When the signal level fluctuates beneath the threshold this affects the noise level, thus breathing and pumping occurs. Just as a compressor, the expander works via a ratio, 1:1 means no expansion whilst 20:1 may cause the expander to act like a noise gate. [4]
43. Why are compressors and gates often used together?
Compressors and gates are usually used together because compression has the effect of bringing down the level of a signal close to the noise floor, when gain make up is applied the overall signal level is brought back up again which in tern raises the level of the noise floor. Thus, a noise gate will have to be used to filter out the noise floor from the processed signal. Thus compression and gating go hand in hand.
44. Comment on envelope shaping using a noise gate.
On a noise gate the attack and decay / release controls are used to manipulate the envelope of the sound. This is done so that there is a smooth, noiseless transition from silence to full signal and back again. Envelope shaping can help in eliminating undesirable occurrences in the signal by adjusting its ADSR [attack, decay, sustain, release]. [4]
45. Comment on gated reverb.
Gated reverb is a technique that was popularised in the 1980s. This is done via the use of a distant mic or a reverberation unit being the reverb source. With gated reverb, the reverberation suddenly cuts off shortly after a note is hit. Such as in the Phill Collins song “In the air tonight” [1]
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Reference:
[1] Studio Recording Engineer
[2] www.sweetwater.com
[3] Sound and Recording – An Introduction, Francis \Rumsey, Tim McCormick
[4] Modern Recording Techniques- DM Huber, R Runstien |
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Sat Apr 02, 2005 5:28 pm |
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JohnA
Joined: 20 Jan 2005
Posts: 28
Location: Mid Glamorgan, UK |
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Audio Course
ACRT03
Week 4
JohnA (mixindown)
1. What is the function of mixing desk automation?
Mixing desk automation allows you to move the faders on the desk and store the movement information to be retrieved at a later date. The faders then move on their own. In complex mixes, many faders may need to be moved (more than a single person can do on their own). With automated faders, a person can mix a complex set of fader movements, save the information, and play it back. All the faders (on a motorised system) will follow the movements that were written for them. Automated mixing desks can therefore take the “riding the faders” out of the mixing situation.
2. Why might the faders have to be moved during the mix?
Sometimes the volume of an instrument may have to be increased/decreased or both during a mix, or there may be a variety of fader movements in a complex mix. At certain instances in a mix, it may be beneficial to take some sounds out of a mix all together to “clean up the track” by decrease background noise (toms). Having automated faders can accomplish this.
3. What aspects of mixing would normally be automated on an analogue console?
Fader movements (as discussed above), channel mutes (mute automation: turning channels on and off during the mix), where parts of a track may not contain any useable audio and therefore could be muted to cut down background noise levels, and also, on some automated mixing consoles, send/return mutes.
4. Comment on VCA vs. Moving Fader automation.
There are two main ways of automating fader levels on analogue mixing consoles. The first is to use motorised faders. The faders are moved by motors which are under computer control. Any movements that you make in write mode are remembered and can be saved for recall later on. Most moving fader systems route the actual audio signal through the fader in the same way that a conventional analogue mixing desk does.
The second method is to use VCA’s (voltage controlled amplifiers). These are controlled by standard manual faders (VCA systems do not employ motorised faders). In the VCA system, no audio passes through the faders, they are simply used to produce a DC voltage that is read by the automation computer to determine the fader position. Unless you have a computer monitor screen connected when using the VCA system, you are at a disadvantage as to the exact position of the fader. This is difficult when listening back to a mix where you want to add edits. To help in this situation, VCA systems with screens attached will often show the physical position of the faders and the virutal level that corresponds to the VCA gain.
5. Describe write/update/read.
Refering to an automated mixing desk, “write” is when you manually control the gain of a fader (with your fingers) and the information is written to an external computer. Read is when the computerised control of the desk “reads” the automation that you have written into it and acts upon this information to automate. VCA automation systems also have “update” or “trim” mode. This allows you to superimpose one set of moves on top of another, without writing over the new moves.
6. How does an automated mix session start?
You could set up snapshot or scene of the starting point of the mix. This would be written in write mode and recalled in read mode as your starting point.
7. How would a section of automation data be re-recorded?
First define your start and end points of the section that you want to re-record. Use “Write” mode during playback to re-record the section you are working on. Make all your adjustments during the re-recording. Save your settings. With VCA automation you can use “update” to re-record.
8. How are automation 'punch-ins' blended smoothly with existing data?
To smoothly blend in punch-ins, use the faders to blend the new data in with the currently recorded data.
9. How could a complex series of moves be increased in level by say 3dB?
You can assign the all the faders to a “group”. This means that when any one of the faders is moved, all the faders that have been selected within that group will move. Put your software in “write” mode and increase any one of the grouped faders by 3dB. Save this data for playback.
10. Describe fader grouping.
Fader grouping is where you assign a number of faders to a “group”. Moving any of the faders in that group moves all the faders assigned to the group. The level of an individual fader is determined at the monent the fader is assigned to the group. This is important as when you move any fader in the group, all the other faders in the group will move relative to each other, i.e. they will all reach the bottom of their travel at the same time when one is pushed in that direction.
11. How could EQ, for instance, be automated using an analogue mixing console?
12. How would EQ be automated using a digital mixing console?
EQ could be automated using the “snapshot” facility on a digital mixing desk. Changes to EQ settings are made and saved with a snapshot. These are then recalled later.
13. What is 'recall'?
Recall is a “snapshot” of all the settings that you have made on a digital desk. You save this snapshot and recall it later to get back to the settings you were on.
14. What advantages does a digital console have over an analogue console regarding recall?
Using recall on a digital mixing desk allows you to take a snapshot of fader positions, EQ and other dynamic steeings, snapshots of entire mix parameters. With an analogue desk, you have to write all these settings down (some engineers even take a photograph of the settings of the desk). With digital desks, all this information can be stored.
15. Does a compressor act upon loud signals or quiet signals? What does it do to the signals upon which it acts?
A compressor acts upon the loudest part of the signal first then acts upon the quietest parts once gain make-up is applied. When the signal exceeds a threshold level that has been set by the operator, the compressor turns the signal down.
18. What is the function of 'make up gain'?
Once a signal has been compressed, the louder parts become quieter. Gain make-up is then applied to bring the audio back to a satisfactory level.
19. How is a compressor usually connected to a mixing console to compress a single signal?
A compressor is usually connected to a mixing console by being patched in to an insert point.
20. How is a compressor connected to a mixing console to compress the entire mix?
It is usually best to connect a compressor to the main stereo buss insert points on a mixing console to add compressor to an entire mix. This would be into the master insert points. The compressor will now be in the signal path just before the master stereo fader(s). This makes it easier to do a fade-out when using a compressor as well as having the added benefit of fading the any noise out as you pull the faders down in your fade mix. Working with mixing desks that don’t have master insert-points, you could patch the compressor between the Stereo-out of the mixing desk and the Input to your stereo master recorder.
21. Explain 'ratio', in the context of compression.
Once the audio signal reaches the threshold, gain reduction is applied. The amount of gain reduction that is applied is governed by the ratio setting. The higher the ratio setting, the more gain reduction is applied. An example would be, if the ratio is set for 2:1, then a signal that exceeds the threshold by 2dB will cause a 1dB increase in output. With a ratio setting of 5:1, a signal that exceeds the threshold by 5dB will cause a 1dB increase in output.
22. Describe the difference between hard knee and soft knee.
With Hard-Knee compression, as soon as the signal reaches the threshold setting, compression or gain-reduction is immediately applied. With Soft-Knee compression, the gain-reduction starts to apply around 10dB below the threshold setting. This gain-reduction is applied gradually so the effect is very gentle to start with. As the signal gets closer to the threshold setting, the degree of gain-reduction gradually increases until the threshold is reached, whereby the full amount of gain reduction is applied. The full amount of gain-reduction is governed by the ratio setting.
23. What are 'breathing' and 'pumping'?
Amongst the controls that many compressors have are usually “attack” and “release”. These controls are there so that you can make the compression come and go unnoticed. Breathing or pumping occurs when the attack and decay times of a signal, (i.e., a snare drum which has a fast attack and release time), are set to be too slow. If the compressor does not start quickly enough, the original transients will get through uncompressed. After the sound has gone, you will hear the compressor gradually reducing the amount of gain-reduction as it returns to normal. So it is the gain-reduction changing rapidly that causes breathing or pumping.
24. What happens if the release time is too long?
If the release time is too long or “fast”, you may be able to hear the level of the signal going up and down causing a “pumping” effect.
25. What does it mean if the gain reduction meter is showing frequent changes?
Gain reduction is applied when a signal reaches the threshold setting so if the gain reduction meter is showing frequent changes, it means that the compression is being applied frequently.
26. Describe the effect of compression on noise level.
When a signal has been compressed, Gain Make-up is applied to bring the signal back to its original high level. By applying Gain Make-up, the quieter audio parts are also increased, bringing up any noise with them. For every 1dB of compression you apply, the signal-to-noise ratio is worsened by 1dB because of the increase in Gain Make-up.
27. Describe the function of the stereo link switch.
A stereo link switch enables a stereo mix that is having compression applied to it to remain balanced, enabling the same amount of gain reduction to be applied to both channels. If, in a stereo mix, a loud sound appears in the left channel and compression is applied only to that channel, the stereo image will drift and the right channel, to which no gain reduction is being applied, will seem to be louder. With a dual-channel compressor, the stereo link switch sums the side-chain inputs together then controls both channels in the same way.
28. What is the side chain input?
A side chain is a separate input on a compressor that allows you to insert a different signal into the compressors “side chain” or “key” input. When a different signal is put into the sidechain, the compressor operates according to the signal fed to the sidechain input rather than to the main input. In other words the main signal (going into the regular input and output) is changed by the level variations of the signal plugged into the sidechain input.
29. Describe a typical use of the side chain input.
Occasionally when recording vocals, certain letters like the letter “s” can stand out. This is called sibilance. Sibilance can be corrected using a technique called “de-essing”. By placing an equalizer in the side chain, you can set the compressor so that the frequencies that are causing the sibliance trigger the compressor to de-ess the vocal.
30. Is a noise gate usually effective on a mixed stereo signal?
It can be. Two gates can be linked to that one controls the other so that when one opens, the other does as well. This can be used in stereo gate situations like over stereo toms.
31. Is a noise gate effective on a signal where the instrument plays all the time?
No. If the gate is to be used, it will have to be set to turn on and off. If an instrument is being played all the time and the gate switches on, the instrument will not be recorded.
32. Is a noise gate effective on a single noisy signal where there gaps in the playing?
Yes. The gate can be set to switch on when the noisy signal is not present (in the gaps). This will cut out any other background noise that is present.
33. Why is it often considered beneficial to gate some or all of the mics on a drum kit (except the overheads)?
If a lot of mics have been used on a drum kit, it is likely that there will be a large amount of “spill” on each track . The mic that recorded the snare drum will probably have picked up the kick drum, cymbals and toms. By using a gate on the snare mic, everytime the snare is struck, the gate opens and picks up the sound of the snare drum. When the gate is closed, the microphone does not pick up any audio and so those sections of the recording are silent. This helps in the mix to cut down the amount of spill on each track, thus cleaning up the whole mix.
34. How many gates are often used in live sound: none, a few or many?
If the volume on stage is going to get loud, it may be beneficial to use some gates on some of the drums. By opening up only when a drum is struck, then closing to reject extraneous noises, gates can clean up a mix and reduce feedback. Specifically, floor toms, rack toms, and kick drum are usually gated in loud situations. The attack and release time of the gates must be set carefully, however, to avoid sounding unnatural or clipped.
35. How is the noise gate connected to the mixing console?
You could patch the noise gate in-line to the insert-point of the channel.
36. What is the function of the Threshold control?
The threshold control on a noise gate sets the level so that the signal can pass if it above the threshold. The noise gate is switched on when the signal drops below the set threshold not letting any signal through.
37. What is the function of the Range control?
On a solo audio signal, the opening and closing of the gate can be noticeable. The range control sets the degree of attenuation when the gate is closed, in other words, how much gain reduction is applied when the gate is fully closed.
38. Comment on the Attack, Hold and Release (Decay) controls.
The Attack setting on a compressor determines how quickly the compressor reacts to the signal when it goes above the Threshold. Signals have Transients (short, sharp peaks) and these can easily trigger a compressor to act. The attack time determines how long the peak should be above the threshold before the compressor attacks and reacts. Transients are important in the clarity of a sound but they don’t affect the loudness of the sound. Higher attack times will let the transients through.
Hold: this function tells the gate that once it is open, to “hold” open for a set time. Then the release time can take over and close the gate. The “hold” function stop the gate from opening and closing too quickly due to peaks. So the purpose of hold is to delay the gate from entering its release phase until after a short time has elapsed once the input signal has fallen back below the threshold.
The Release time determines how quickly the compressor will let go (release) and restore normal gain. You have to be careful not to set the Release time too fast for the amount of gain reduction applied. If the signal starts to go into a kind of loop (through the threshold then back to normal gain, over and over very quickly) pumping can occur (as described above). This is because the gain structure is changing rapidly. Instruments that have long sustain notes, such as bass guitars, usually record better with slower release times. Sharp percussive instruments such as snare drums, usually benefit from faster release times.
39. What would happen if a stereo signal was gated, but the stereo link function was not selected?
If the stereo link function was not selected then the gate could be triggered on either side of the signal cutting out one of the channels tolally.
40. Why are side-chain filters beneficial?
As an example, gating is easier when the sound source is well differentiated between the signal and the noise or sound you want to gate out. However, there are times when the noise is at such a high level, that setting the threshold to the point where it fits neatly between the signal and the noise is almost impossible. This is where a Noise Gate side chain filter comes in. The side-chain on the gate can be used to control the behaviour of the processed signal. This is commonly called the “trigger” or “key” signal. Often, when miking a snare drum and hi hat, the snare mic will often pick up as much level from the hi hat as it does from its own instrument. To stop the hi hat signal from opening the sate on the snare mic, simply filter out the high frequencies from the key. The low frequencies contained in the snare sound are sufficient to open the gate for the snare, but the lesser low frequency content of the hi hat signal in not enough to do the same. To stop the hihat from opening the gate on the snare mic, simply filter out the high frequencies from the key. The snare is sufficiently rich in low frequencies that it will still open the gate, but the lesser LF content of the hihat is not enough to do the same.
f there was a mic on the hihat suffering from the same problem, then the low and mid frequencies could be filtered out of the key, and the rich high frequency energy of the hihat would still open the gate.
One important point to note is that the filters have no effect on the frequency balance of the output signal. They only affect the key, which once it has done its job goes nowhere.
There is a function, here called 'key listen' that switches the key signal to the output. This can be used for setting up the gate, then switched back to 'gate' for normal operation.
41. Comment on the use of an external key to improve the reliability of gating.
As above.
42. What is an expander?
Expanders are similar to gates in that their job is to either reduce or eliminate unwanted background sound or noise. Setting a gates range of controls to maximum, will completely silence any signal that falls below the threshold. An expander works more like a compressor, but in reverse. It applies gain reduction to the signal or noise once it is below the threshold. Like a compressor, you set the ratio settings on an expander to get rid of the noise in varying degrees. So a 1:3 ratio means that for every decibel the input fell below the threshold, the output will fall by 3dB. This gradual noise reduction means that it acts like soft-knee does with a compressor, by not attacking the noise head on.
43. Why are compressors and gates often used together?
Using a noise gate after the compressor will turn off the signal when the instrument isn't playing. Some (more expensive) compressors have noise gates built in for this reason.
44. Comment on envelope shaping using a noise gate.
The compressor can shape the envelope of the sound by emphasizing the attack (by setting a slow attack time on the compressor, allowing the initial transient to get through unaltered), or by allowing the reverb to increase in level as the drum dies away.
The noise gate can then further process the envelope using the attack, hold and release controls.
45. Comment on gated reverb.
Gated reverb is where the reverb get abruptly cut short by a gate on the returns.
To set up a gated reverb on a snare drum, mic a snare drum up and route the signal to a reverb unit with a medium room preset. Route the output of the reverb through a stereo noise gate (or you can patch a stereo noise gate into the reverbs return channels) and set both very fast attack and release times. Adjust the hold time to taste but carefully set the threshold to avoid “fluttering” during the final part of the reverb tail.
For more accurate triggering of the noise gate, take a feed from the drums into the gate's side-chain so that the percussive attack from the drums is used to trigger it, rather than the onset of the reverb alone.
JohnA (mixindown)
http://www.soundonsound.com/sos/jan00/articles/mix.htm
http://www.soundonsound.com/sos/jan00/articles/mix.htm
http://www.soundonsound.com/sos/Jun03/articles/pronotes0603.asp
http://www.soundonsound.com/sos/1994_articles/aug94/mixautomation.html
http://www.soundonsound.com/sos/mar05/articles/qa0305_3.htm
Live Sound Reinforcement: Scott Hunter Stark
Home Recording For Musicians: Craig Anderton
http://artistpro.com/index.php?module=PnCourses&func=getPage&course_id=16&page_id=51
http://www.record-producer.com/learn/noise-gate-effects.html
http://www.harmony-central.com/Effects/Articles/Expansion/#why |
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Sun Apr 03, 2005 8:37 am |
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Quinnersboy
Joined: 22 Mar 2005
Posts: 4
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| Questions for week 4 |
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1.What is the function of mixing desk automation?
Mixing is an important job when recording is involved. When recording mixes as much accuracy as possible must be gained. Automation sound desks leave the job of mixing more a one-man job than a couple depending on the scale of the mix. Automation is a mixer that has an external computer or a built in one, depending on price range controlling or giving instructions to the engineer on what to do and when to do it.
2. Why might the faders have to be moved during the mix?
Each channel has it’s own fader. As the fader is moved the level is either raised or lowered. As the fader moves it controls the level of that channel being sent to the master volume. For example if the keyboard had to be turned down for a guitar solo then the fader on the keyboard channel on the desk would be pulled down to reduce the level.
3. What aspects of mixing would normally be automated on an analogue console?
The most common component to be automated is the channel levels. Anything else would be unusual but some other components that can be automated are the mutes and the master stereo output level.
4. Comment on VCA vs. Moving Fader automation.
VCA stands for Voltage controlled amplifiers. VCA’s automation has no audio signal flowing through the faders. Instead a DC voltage is fed through each fader, which is read by the automation computer, which in turn determines the fader position and makes the adjustment automatically. VCA is popular because the moving fader system or motorized fader system is very expensive in contrast to this system. The one disadvantage to this system is that when the mix is playing back the faders don’t actually move which gives you no feedback or indication of where the levels actually are unless you had a system that could accommodate a computer monitor screen.
5. Describe write/update/read.
Write is a term used when recording data on an automation console. With manual consoles we say we will record now, but with automation consoles we say we will write now. Update is term used to describe adjustments made to written data. You are finished writing and you feel that some adjustments need to be made to the data, but the faders are not at the best possible positions. Some are half way, yet further ones are near the very bottom, and then an update will need to be done. On the console there is a mode called trim, which enables you to move the faders to a more reasonable position with disturbing the gains of the VCA’s. While in this mode the written data does not be replaced or deleted but just modified. The term read is when the console does everything automatically. When in the write mode, the engineer does all the work. But when in read mode the computer does all the work. When writing the computer records every movement made on the desk and every adjustment made, so when it comes back to playback you just sit back and listen to what you have produced.
6. How does an automated mix session start?
7. How would a section of automation data be re-recorded?
Chose the section of data in which you want to re-record. Then place a cue at the beginning and end points of the section. Then play back your data while the console is in write mode. Make all necessary changes to the fader positions or what ever you have to do then save your changes. Then hit the update button and the data will be added to the track leaving you with your existing data that is fine and the new data inserted to give you a perfect mix.
8. How are automation 'punch-ins' blended smoothly with existing data?
A cross fade between the automation punch in and the existing data can be done to provide a smooth blend in off both tracks. Once the levels are the same between the punch in and the existing data then the punch in will be added and not be noticeable.
9. How could a complex series of moves be increased in level by say 3dB?
To move a number of faders up by 3db then the selected channels would need to be put into a subgroup. Once in that sub group the selected faders can be moved up by 3db. Depending on the console weather is an automation console or a manual one will depend on how this is carried out. For the automation console the selected faders would be in the subgroup. Moving any one fader moves the whole selected group together. If increasing a complex series of moves then the automation console is the best for the job. It will be more accurate in performing the moves.
10. Describe fader grouping.
Fader grouping is a selection of faders in a group, which is assigned to a subgroup, which has a master fader to control that group. The level of each channel has to be set at it’s own fader. Once the relative level has being set for each channel then the overall volume of that selected group can be controlled by the master level for that group. It’s necessary to use the consoles routing busses to undertake this operation. This is the case with the normal mixing console. With the automated mixers the faders within the subgroup don’t necessarily need to use the routing busses of the console. Once the faders have being assigned to a group then moving any of the faders within that group adjust all the levels but still maintaining the desired level required.
11. How could EQ, for instance, be automated using an analogue mixing console?
For automation of eq in an analogue console then some other equipment will be required to undertake this task. As the faders and mutes can only be automated in an analogue console the eq most be automated using a computer.
12. How would EQ be automated using a digital mixing console?
Eq’s can be automated using recall or snap shots. Once the positions of the Eq’s have been set then a snap shot of those positions can be taken by the console. Many of these snap shots can be taken if lots of changes have to be made in the eq settings. Once taken these can be implemented at the appropriate time during the mix to give accurate transaction between eq changes.
13. What is 'recall'?
Is a term used to describe a place where all data about eg’s, fader positions, effects and so on is recorded and stored in memory for that particular time. Also know as a snapshot this information can be retrieved automatically at the approximate time in the mix saving time editing and repositioning faders to acquire the desired sound.
14. What advantages does a digital console have over an analogue console regarding recall?
A digital console can store more recalls and can store more information on each recall. The analogue console can only store fader position and mutes, where the digital console can store information on fader positions, eq’s, pan, aux, effects, dynamic settings and mutes. Therefore the digital console for recall has the upper hand just because it can store more information lessening the work for the engineer.
15. Does a compressor act upon loud signals or quiet signals? What does it do to the signals upon which it acts?
The compressor acts upon the loud signals. When the signal comes into the compressor it contains peaks. The compressor removes these peaks over all reducing the level of the signal. These means that the signal then can be increased even more to get more out of over all mix.
18. What is the function of 'make up gain'?
Make up gain is to increase the level of the signal. Once the signal goes into the compressor, it removes the peaks from the signal leaving it quieter than in entered. Therefore it is necessary to bring it up to the same level so make up gain is added to bring is back to the original level.
19. How is a compressor usually connected to a mixing console to compress a single signal?
To compress a single signal the compressor can be connected through the aux send and return of a mixing console. The signal is connected to the mixing desk through its usual position. Then a lead is taken from aux send to the input of the compressor. Then another lead is taken from the output of the compressor to the aux return input on the console. This is how a compressor can be connected to a mixing console to compress a single signal.
20. How is a compressor connected to a mixing console to compress the entire mix?
To compress the entire mix then the compressor is introduced just after the mixed signal has left the console heading to the amplifiers. The outputs of the desk are connected to the inputs of the compressor and then the outputs of the compressor are connected to the inputs of the amplifiers. This then compresses the entire mix leaving more room to get more volume out of the mix without the problem of clipping.
21. Explain 'ratio', in the context of compression.
Ratio is a term used to describe the amount of compression of an input signal to the out going signal. If the ratio is 4:1 then for every 4 dbs above the threshold the output signal will be 1 db over the threshold. Same again in the setting on the compressor is set to 10:1 then for every 10dbs above the threshold then the out going signal will be reduced to 1 db above the threshold. The higher the ration the less of an out going signal will be sent.
22. Describe the difference between hard knee and soft knee.
Soft knee is shift from unity gain to compression at the threshold of compression is gradual instead of a straight line. Soft knee threshold is smooth and increases gradually instead of a sudden change. The hard knee is the opposite of soft knee. Hard knee will shift from unity gain to compression suddenly.
23. What are 'breathing' and 'pumping'?
Breathing and pumping are effects produced because of sound modulation. As a signal goes up and below the threshold so do the noise levels also. This effect is undesirable so changes must be made to settings to avoid it.
24. What happens if the release time is too long?
If the release time is set is too long then an effect called pumping can be produced. The reason for this is that the release is to fast for the amount of gain reduction applied, and then the return to normal gain over and over again as the signal continues to move above and below the threshold. Basically the pumping effect is caused by the gain structure changing quickly.
25. What does it mean if the gain reduction meter is showing frequent changes?
If the gain reduction meter is showing frequent changes then this means that there are a lot of changes in the levels, which are coming to the compressor. This can either be from different levels being produced by the musician or that the vocalist is moving back and forth on the mic.
26. Describe the effect of compression on noise level.
When the signal is compressed the peaks levels are brought down somewhat. This signal is now down near the floor noise. Once the make up gain has being added both signal level and noise level will be increased to compensate for the reducing in the peaks bring removed. So this means that the floor noise level now also has being risen and can become more noticeable when all playing stops.
27. Describe the function of the stereo link switch.
A stereo link switch function on a noise gate is used when applying a double channel gate to a stereo signal. If using an old analogue unit for instrument amplification then the stereo link switch would be used. What is does is that it forces both gates to open and close together producing a nice clean sound. However if you leave the stereo link switch of when trying to gate this instrument the signal will sound terrible no matter how well you try to set the threshold as both channels will change shape at different times.
28. What is the side chain input?
A side chain input is a signal used to control the conduct of the processed signal. In a noise gate this most commonly called a trigger or key signal. If the controls where set to there end and stop positions then the signal being used to control the gate would be the same as the input signal. Once you fiddle about with these settings on the filters then a more accurate opening and closing of the gate can be acquired.
29. Describe a typical use of the side chain input.
A typical use of a side chain input would be on a drum kit. The snare and the hi-hat are the most common problems in setting the threshold for the noise gate. When the drums are set up the snare and hi-hats are very close together. When the mics are in place and sound is being produced you find that the snare is setting of the hi-hat gate and vice versa. The reason for this is that there is pretty much the same level coming of both instruments causing the gate to open for both instruments. To stop this the side chain function would be used on the gate. To set this for the snare and hi-hats some adjusting on the filters will be required. If you reduce the high frequencies from the side chain filters then the gate will only open for the snare as the snare produces a more lower frequency sound than the hi-hats. With the hi-hat side chain filters you reduce the lower and mid frequencies from the side chain filters leaving just the high frequencies to set of the gate, as the hi-hats produce a more higher frequency output than the snare. This will then leave that the snare will only open the snare gate and the hi-hat will only open the hi-hat gate solving the problem of both gates staying open all the time.
30. Is a noise gate usually effective on a mixed stereo signal?
No a noise gate can only process a signal unmixed signal coming from an instrument of mic. It can’t determine when to open of close in a mixed stereo signal.
31. Is a noise gate effective on a signal where the instrument plays all the time?
If the instrument is playing all the time well then it wouldn’t be necessary to have a | | | |
