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Audio Resources

Audio CablesDirect Injection (DI) BoxesCommon Microphone TypesCommon Microphone Pickup (Polar) PatternsWireless Headset MicrophonesExample Microphones

Audio Cables

NOTE: Unbalanced cables (two internal wires, a conductor and ground wire) are at higher risk of picking up interference and noise. Balanced cables are designed to cancel out interferences and noises (these cables have an addition internal conductor wire that negates interference and noise). For a connection to be balanced, every connection in the signal chain must be a balanced connection, this includes the source output, the cable(s), and the input connection. If a single part on the chain is an unbalanced connection, then the connection is unbalanced.  Check the source is physically connected to the system and power is provided to any components as required.

Balanced cables. 

Can be long in length and won’t pick up noise and interference. 

TRS cables are identifiable by the two “stripes” on the connector tip. They are balanced if connected to balanced devices in mono. If this is not the case, they are unbalanced (this is because if a single cable is used in stereo, both conductor wires will be used for the signal, resulting in no conductor cable available to provide noise cancelling).

TS cables are marked with a single stripe on the connector tip and are useful for mono outputs. TS cables are always unbalanced and are always mono. Keep these cables as short as possible in order to mitigate noise and electrical hums. 

Mostly come in pairs to achieve a stereo signal. Commonly used for DJ and home equipment. RCA cables are always unbalanced and therefore any RCA cable runs should be as short as possible.  

Midi does not transmit sound. This type of cable is used to transmit digital information called “event messages”. These are instructions including information like: Note ON/OFF, notes played, Velocity, Aftertouch, Tempo, Planning, Volume, etc. 

Often found on MIDI controllers, audio interfaces, modern synths, drum machines, etc. USB is used to exchange information between music gear and computers (some USB also can be used for MIDI information). 

Used to send speaker-level signal from power amplifiers to the PA.

Direct Injection (DI) Boxes

DI boxes are used to convert signals from an unbalanced connection into a balanced connection. 

There are two types of DI box:

  • Passive DIs (powered signals): used with higher signal instruments. and,
  • Active DIs (unpowered signals): used with low signal instruments.

Common Microphone Types

Condenser microphones work using capacitance (electrostatic charge). They tend to have higher sensitivity, have less durability, require external power (phantom power), and have wider frequency responses.

Useful for hi-hats (for example the AKG C451 B), overheads (for example RØDE NT5), and things like strings (especially in clip on form).

Work the same as other condenser microphones however the diaphragm is larger and therefore provide greater low frequency detail and audio information.

Can be useful for overheads, stereo setups, brass, etc… however the pickup pattern and frequency response pattern of these microphones are more likely to be used as ambiance microphones or overheads in a live environment (if at all).

Dynamic microphones are great for live performances. This is due to them working via electromagnetic induction and having a higher durability due to their handling of high sound pressure levels. They tend to have lower sensitivity than condenser microphones and a narrower frequency response however don’t require an external power source.

Common Microphone Pickup (Polar) Patterns

Picks up sound from all directions around the microphone. In a live environment they have to be positioned close to their source in manage ambient noise and risks of feedback (this pattern is often found on lapel microphones)

 

Has a wider “listening area” focusing on the area directly in front of the microphone. This type of pattern is best used for single source capture in close proximity to the microphone.

Note: all cardioid-type pickup patterns will exhibit what is called the proximity effect. This means that the effect occurs at an increasingly greater strength the closer the microphone gets to the source. The effect is that there is an increased sensitivity in bass frequencies.

 

Narrower forms of the cardioid pattern however consequently pick up some sound from directly behind the microphone. Often used for targeted / directional capture of audio. Supercardioid (also known as shotgun) patterns in general are like hypercardioid (also known as mini-shotgun) patterns, however, capture slightly less rear noise. 

Typically found on large diaphragm condenser and ribbon microphones. Picks up sound from the front and back whilst rejecting sound from the sides.

Wireless Headset Microphones

Setting up a wireless headset microphone often requires a little more care and attention. Often these microphones are omnidirectional dynamic microphones and therefore pick up sound sources from all directions. Therefore, use of these microphones requires it to have the source (mouth) as close to the microphone as possible and the gain staging correct to minimise the risk of feedback, distortion, and unwanted noise. As a general rule of thumb:

  • Adjust the microphone headset so the microphone sits about 1cm just behind and below the corner of the mouth.
  • Make sure the gain on the wireless pack, and receiver, are all at peaking at approximately -18 to -12 dB (yellow maximum). 
  • Use channel preamp gain to balance the sensitivity of the mic and use EQ to eliminate the most sensitive frequencies. 

Example Microphones

Shure SM58 (dynamic microphone) 

The “workhorse” of vocal microphones. Can also be used with guitar and bass amps if necessary. 

Shure SM57 (dynamic microphone) 

“All-rounder” microphone often used with cabs, snares, and other louder instruments). 

Shure Beta 52 / Audix D6 (dynamic microphones) 

Kick drum “outside” microphone. 

Shure Beta 91 / Beta 91a (condenser microphones) 

Kick drum “inside” microphone. These are omnidirectional boundary condenser microphones, designed to be placed on a flat surface. 

Sennheiser 904 / Sennheiser 604 (dynamic microphones) 

Clip on dynamic microphones useful for toms, brass, strings and other instruments requiring clip on microphones. 

ATM 350 (condenser microphone) 

Clip on condenser microphone useful for toms, brass, strings and other instruments requiring clip on microphones. 

DPA 4099 (condenser microphone) 

Clip on condenser microphone useful for strings, woodwinds, percussion, and other instruments requiring clip on microphones. 

Sennheiser e609

Supercardioid dynamic microphone designed for guitar cabinets but also useful for drum overheads and brass instruments. 

Signal ChainGain StagingEqualisation (EQ)CompressionSends & ReturnsMixSound LevelsUseful Terminology

Signal Chain

 Check the source is physically connected to the system and power is provided to any components as required.

Gain Staging

Gain allows us to increase or decrease the signal strength of a source. Check every gain setting on every component from the source through to the mixer. Adjust preamp gain on channels until there is a healthy signal (signal is turning "yellow" at its loudest is a good rule of thumb, this tends to be a peak level between -18dBFS and -10 dBFS). All channels, buses, and plugins need to avoid clipping. Leave some headroom on any master bus (peak levels between -10dBFS and -6dBFS with healthy average levels is a good rule of thumb).

For (sensitive) microphones you may find it helpful to lower the preamp gain slightly to manage feedback issues, for example in setups where microphones are used in front of a speaker line. 

NOTE: Too much gain causes distortion, too little gain and the source signal will be weak (too quiet). Increasing the gain will have the effect of an increased “sensitivity” of microphones.

Equalisation (EQ)

EQ provides the process used to control what "part of the sound frequency spectrum" you do and do not want from a source. I can be done by making adjustments on what is often visualised as a frequency graph. Parametric EQs (PEQ) have three basic settings:

  • Frequency: selects the frequency band (value) you wish to edit around. 
  • Gain: determines the reduction or increase applied to the audio at the frequency band. 
  • Q: determines how “wide” or “narrow” the adjustment is where lower values will provide a wider band (impacting a greater number of frequencies). 

Other than PEQs and GEQs there are three other common EQ types:

  • HPF: High Pass Filter cuts all frequencies below a set value. 
  • LPF: Low Pass Filter cuts all frequencies above a set value. 
  • Low / High Shelf: Applies any changes to frequencies below or above a set value. 

Compression

Compression is used to manage and control the levels, character, and shape of the transients (hardness / softness) of a track, specifically this is done by managing the dynamic range of a signal. The primary components of a compressor are:

  • Threshold: determines the signal input level at which the compressor will start engaging. 
  • Ratio: the ratio at which the compressor will reduce the output at the threshold (higher ratio provides a higher compression) 
  • Attack: the “reaction time” of the compressor after the threshold has been achieved by a source
  • Release: the delay before the compression lifts off after the signal has returned past the threshold 
  • Out (make-up) Gain: additional gain used to boost the source 
  • Knee: softening / hardening of the compression impact at the threshold point

The amount of compression applied to the track is often visualised as a red bar showing the reduction in dB provided as a result of compression. A rule of thumb is about -6dB of compression with approximately 3 to 6 dB of Out Gain. The intent of this type of compression would be to increase the overall output of the track (using Out Gain) and then temper the “loudest” parts, bringing the quietest and loudest parts of a track "closer together", known as a reduction in the dynamic range.

Sends & Returns

This selection allows you to send channel signals to a MIX out. Sends are often used for IEMs and also sending channels to effect racks (which are then "returned" to outputs as desired). The FX return is therefore the channel that controls a rack's output to a mix.

Mix

Some tips to consider regarding the mix (the volume of individual components in relation to each other): 

  • Usually the loudest acoustic instrument will dictate the minimum volume of a mix. This is often an acoustic drum kit, especially when it is in an untreated environment with no cage or shielding. 
  • The key channels to get placed correctly in a mix are the LEAD VOCAL and often the LEAD INSTRUMENT (usually providing the tone / key and rhythm for any music, for example a rhythm guitar and drums). Ultimately, events require three key factors, can the vocals be heard, are they intelligible, and is the system able to effectively “communicate” and deliver any intended impact on a room and to the listener(s). The rest of a mix balances around facilitating these things. 
  • It can be helpful to begin by mixing the lead (or primary) components with the loudest acoustic instrument to the desired volume in the room. After this start to bring in other instruments and vocals to “sit” in any gaps in a mix. If you find things clash or multiple instruments or vocals sit in the same range and create issues, do not be afraid to reduce or remove a channel to manage the mix (this is common when there are same or similar instruments playing or vocalists sing in the same range as others). 

Sound Levels

The Health and Safety Executive (HSE) recommends that the following sound levels (for live events) are not exceeded:  

  • Continuous sound level: The A-weighted equivalent continuous sound level (Event LAeq) should not exceed 107 decibels (dB) in any part of the audience area.  
  • Peak sound pressure level: The C-weighted peak sound pressure level should not exceed 140 dB.  
  • Audience separation from loudspeakers: The audience should not be allowed within 3 meters of any loudspeaker.  
  • Audience notification: If the Event Leq is likely to exceed 96 dB(A), the audience should be advised of the risk to their hearing in advance. 
  • Noise from pyrotechnics should not exceed a C-weighted peak sound pressure level of 140 dB at head height in the audience area. 

Another useful guideline is the UK's Control of Noise at Work Regulations 2005 which set out limits for noise exposure in the workplace:  

  • Exposure action value (EAV): Daily or weekly exposure of 80 dB(A) or peak sound pressure of 135 dB(C). 
  • Upper exposure action value: Daily or weekly exposure of 85 dB(A) or peak sound pressure of 137 dB(C). 
  • Exposure limit value: Daily or weekly exposure of 87 dB(A) or peak sound pressure of 140 dB(C). 

Action must be taken to reduce the risk if the noise exposure is at or above the EAV. Actions include providing hearing protection, implementing noise control measures, assessing the risk to workers' health, providing information and training to workers, and considering appropriate work schedules with adequate rest periods. Weekly personal noise exposure can be used instead of daily personal noise exposure if an individual’s exposure varies from day to day. 

Useful Terminology

A device that boosts or cuts selected bands of frequencies in the signal path. 

The act of boosting a frequency and then changing the frequency being boosted until a specific (usually unpleasant) frequency is found. Once found, that frequency can be isolated and then removed. 

The “howling” or “ringing” sound caused by bringing a microphone too close to a loudspeaker driven from its own amplified signal. 

The number of times an event repeats itself in each period. Generally, the time for audio frequencies is one second, and frequency is measured in cycles (or wavelengths) per second, abbreviated as Hz. One Hz is one cycle per second. One kHz (kilohertz) is 1000 cycles per second. 

The variation in level of a signal. Proper gain structure within a sound system allows for maximum dynamic range and the minimum level of noise a system is capable of generating. 

The available signal range above the nominal level before distortion occurs. Headroom may be thought of as a safety margin that allows room for all those dynamic peaks that give impact to music. 

The high point in signal level. Where clipping or distortion begins. 

The +48V power supply available at the channel mic inputs, for condenser mics and active direct boxes.

Controls the bandwidth of an equalizer (the range of frequencies that will be affected). A higher Q value results in a narrower bandwidth (a steeper EQ curve) and therefor a smaller range of frequencies are impacted by any change (useful for targeting specific frequencies). A lower Q value results in a wider bandwidth (useful for smoother adjustments across a range).

The sound remaining in a room after the source of sound is stopped. It's what you hear in a large room immediately after you've clapped your hands. 

The ringing in the ears that often results from prolonged exposure to very loud sound levels. 

When a gain-providing circuit is set for zero boost. Settings at unity gain typically ensure balanced signal levels and help protect against feedback. 

The Audible Frequency RangeInstrument Mix PlacementEQ and Compression TipsEQ and Compression Settings

The Audible Frequency Range

The below information is a rough guide to start training your ears what to listen for in each frequency range.

Too much: RUMBLE
Too little: WEAK

Sounds in this range are often 'felt' more than heard. They provide an effect of 'power' in the audio.

Too much: BOOMY
Too little: WEAK

This range contains the fundamental frequencies of rhythm sections (primarily bass instruments and kick / low drums live in this range). Changes made here will alter the musical balance - too much in this range sounds 'boomy' (or 'fat'), too little and the audio will sound 'weak' ('thin').

This range has a 'telephone' or 'old time radio' like quality given to the audio if it is the dominant frequency range. A number of audio source types live in this range which means that 'muddying' this range (when multiple audio sources compete with each other in the same frequency range) can occur quickly and intelligibility in this range can suffer.

250 - 500 hz controls the 'boom' ('warmth', 'mud', or 'boxiness') of the audio. Too much can muffle the audio, and too little creates a 'transparent' (or 'thin') sounding audio.

Too much: MUDDY
Too little: THIN

500 hz - 1 khz provides a 'horn' or 'honk' like effect in the audio.

Too much: BOXY / HONK
Too little: HOLLOW

1 - 2 khz provides a 'tinny' effect in the audio. Note, that excess output in this part of the midrange can cause listening fatigue.

Too much: TINNY
Too little: SCOOPED

Too much: HARSH
Too little: DISTANT

This is a key range for the 'presence' and 'solidity' of audio, especially in a mix. Key sources can be brought 'forward' in a mix through creating space in this range for them. Too much volume and exposure to this range can cause listening fatigue.

Too much: HARSH
Too little: DISTANT

This range is responsible for clarity, intelligibility, and definition of a source. Adjusting the frequencies in this range can determine how much a source 'stands out' by making it seem 'closer' or more 'distant' ('transparent') in a mix. The attack of percussion and rhythm instruments tend to sit in this range.

Too much: PIERCING
Too little: DULL

This range is a higher frequency range which commonly is the home to cymbals and the 'sparkle' of a source. This higher end of the vocal frequency spectrum lives here too. This range can also cause ear fatigue and when too prominent, it creates a 'shrill' like tone. Sibilance often lives in the 5 - 10 khz range (heard in the 's' sound from vocals). Too little of this frequency range will make a mix sound 'dark'.

Too much: HISS
Too little: LIFELESS

This range controls the 'brilliance and 'clarity' of an audio source and can provide 'air' in a mix. This range often provides a sense of high fidelity in audio however if there is too much of it, it can cause 'hissing', 'imbalance', and ear fatigue.

Instrument Mix Placement

Like above, the graphic information below is not intended to be hard and fast rules for what exactly occurs in each frequency range. It will allow you to look for, and start to tailor, how you want a source to sound based on a rough estimation as to what part of it lives in each frequency range.

EQ and Compression Tips

  • Frequency sweep to find track “sweet spots” (where they sound best). EQ in mono to hear frequency competition. 
  • "place" instruments in the mix and remove competition for frequency ranges. Mixing at a higher volume helps for mixing the low end, then turn the mix to a low volume to general adjustments. 
  • Cut with a narrow Q value (the value determining how wide the cut is). Boost with a wide Q value. 
  • Tactful frequency boosts can help shape or make an instrument sound "different". 
  • When you are happy with a mix, step out of the room to let ears rest / reset. Walk around the room assessing sound in different locations. You should be considering things like: 
  • Do the speakers cover the full width and depth of the audience? 
  • Are there any frequencies on stage that are “hot spots” (louder than other frequencies) and therefore may cause feedback if picked up on by a microphone? 
  • Are bass frequencies more noticeable in specific areas of the room? 
  • You will notice that you mix will sound different in the room with the room empty, and the room full of people. Once full you should expect some absorption in the lower frequencies, and the full mix to “tighten” as there are less indirect soundwaves moving through the room. 
  • Slower attacks emphasize initial sounds (useful for drums, etc...) 
  • Faster attacks soften transients and emphasises ambience (useful for overheads, rooms, etc...) 
  • Higher ratios of compression for more obvious compression (intensity, useful for overheads, ambience, etc… and sometimes vocals) 
  • Lower ratios for transparent compression 
  • Compression is used in order to manage and control the levels, character, and shape of the transients (hardness / softness) of a track 

EQ and Compression Settings

EQ Frequency Cuts:

  • < 50 hz (HPF) unwanted rumble 
  • 150 - 350 hz mud 
  • 700 - 900 hz box and 'basketball' sound

Fundamental Frequencies:

  • 40 - 60 hz low-end 
  • 60 - 145 hz body and weight 
  • 2.5 - 4.5 khz slap 
  • 8 khz click and air

Compression:

  • Attack: slow 
  • Release: fast

EQ Frequency Cuts:

  • ~100 hz (HPF) 
  • 500 - 700 hz boxiness

Fundamental Frequencies:

  • 200 - 400 hz low-end and body 
  • 250 - 600 hz ring 
  • 2 - 4 khz midrange attack and smack 
  • 8 khz crack and snap

Compression:

  • Attack: slow 
  • Release: fast

EQ Frequency Cuts:

  • ~40 hz (HPF) 
  • 150 - 300 hz mud and boom 
  • 700 - 900 hz box and 'basketball' sound

Fundamental Frequencies:

  • 70 - 90 hz (floor toms) low-end  
  • 120 - 200 hz (rack toms) low-end  
  • 150 - 300 hz weight and body 
  • 3 - 5 khz smack and attack 
  • 8 khz presence, attack, and air

Compression:

  • Attack: slow 
  • Release: fast

EQ Frequency Cuts:

  • ~100 - 200 hz (HPF)
  • 400 - 700 hz box and kit sound

Fundamental Frequencies:

  • 200 - 400 hz clank and gong 
  • ~6k - 15 khz (shelf) high-end sheen

Compression:

  • Attack: medium-fast 
  • Release: fast 

EQ Frequency Cuts:

  • 150 - 350 hz mud
  • > 8 khz harshness

Fundamental Frequencies:

  • 80 hz low-end 
  • 5 - 8 khz presence

Compression:

  • Attack: fast 
  • Release: fast 
  • Hard compression to 'bring out' ambience 

EQ Frequency Cuts:

  • 80 - 200 hz mud
  • 350 - 700 hz boxiness 
  • ~4 khz (LPF)

Fundamental Frequencies:

  • 50 - 80 hz sub and low-end 
  • 80 - 200 hz definition and body
  • 1 - 1.5 khz attitude and cut through mix 
  • 2 - 5 khz presence, grind, and strings

Compression:

  • Attack: medium
  • Release: medium-fast

EQ Frequency Cuts:

  • > 70 hz (HPF) 
  • 250 - 600 hz mud and boxiness

Fundamental Frequencies:

  • 80 - 400 hz body  
  • 200 - 400 hz wood sound range 
  • 500 - 1 khz warmth and fullness 
  • 1 - 2.5 khz cut through and definition 
  • 7 - 12 khz attack, brightness, and air

Compression:

  • Attack: medium
  • Release: medium

EQ Frequency Cuts:

  • 90 - 120 hz (HPF)
  • 250 - 350 hz mud
  • 9 - 12 khz (LPF)

Fundamental Frequencies:

  • 300 hz - 1 khz character
  • 1 - 2 khz cut through mix and honk
  • 2.5 khz aggression
  • > 3 khz presence, attack, and brightness

Compression:

  • Attack: medium
  • Release: medium-fast

EQ Frequency Cuts:

  • 50 - 250 hz boom and mud
  • 800 hz - 1 khz bark

Fundamental Frequencies:

  • 1.5 - 2.5 khz presence
  • 2.5 khz aggression
  • 5 - 9 khz attack and clarity

Compression:

  • Attack: medium
  • Release: medium-fast

EQ Frequency Cuts:

  • > 100 hz (HPF or low-shelf) mud and woof
  • 200 - 500 hz mud
  • 800 hz - 1.5 khz honk and nasal

Fundamental Frequencies:

  • 1 - 2.5 khz up-front in mix
  • 2.5 - 4.5 khz presence and definition
  • > 5 khz clarity
  • 8 khz aggressive brightness
  • > 10 khz air

Compression:

  • Attack: medium-fast (slower for harder consonants)
  • Release: fast
  • harder compression

EQ Frequency Cuts:

  • > 100 hz (HPF or low-shelf) mud and woof
  • 1 - 2.5 khz lead vocal space

Fundamental Frequencies:

  • 800 hz fullness
  • 3 - 4.5 khz definition
  • 12 khz air and brightness

Compression:

  • Attack: fast
  • Release: fast