FOH Mixing Consoles,Microphone Selection, Racks,

and Wiring

D. G. MeyerSchool of Electrical & Computer

Engineering

Outline – Mixing Consoles• FOH Console Criteria• Representative FOH Console• Sample Analog Consoles• Sample Digital Consoles• Choosing Analog or Digital

FOH Console Criteria• Inputs (number/type/phantom power)• Channel inserts• Number of mix buses and groups • Number of masters (L/C/R)• Number of aux sends/aux returns• Number of aux sends/aux returns• Meter bridge• Channel input gain/attenuation• Channel EQ (parametric/shelving)• Monitoring (PFL/AFL)• Matrix output mixer• Automation (programmable scenes)

Representative FOH Console

Yamaha IM8

Typical Channel Strip

Typical Channel Strip

Signal Flow Diagram

Group/Aux Bus

Master Section

Matrix Section

Control Section

Sample Consoles• Allen&Heath• Mackie• Midas• Soundcraft• Yamaha• Yamaha

Choosing Analog or Digital• Analog consoles

– generally more “intuitive”– generally less expensive– limited “scene setting” capability– With VCA, increased automation capability– With VCA, increased automation capability– physically large for large number of channels

• Digital consoles– generally less intuitive (but more “foolproof”)– generally more expensive– extensive “scene setting” capability– generally more compact (multi-function faders)

Outline – Microphone Selection• Microphone Characteristics• Pickup Patterns• Directional Characteristics• Balanced Lines• Musical Instruments• Musical Instruments• Effects and Rules• Wireless Systems• Frequency Bands and Intermodulation

Effects• Diversity Principle• Antenna Types

Microphone Characteristics• Dynamic

– employs diaphragm/voice coil/magnet assembly

– rugged, relatively inexpensive– can handle large SPL– can handle large SPL– generally unaffected by heat/humidity

Microphone Characteristics• Condenser

– based on an electrically-charged diaphragm/backplate assembly that forms a “sound -sensitive capacitor”

– electric field between diaphragm and backplate is proportional to spacing backplate is proportional to spacing between them

• Maintaining charge– electret: permanent

charge (special material)– non -electret: need

polarizing voltage

Microphone Characteristics• Condenser

– all types require additional active circuitry to create an electrical signal compatible with standard microphone inputs

– requires batteries or phantom power (48 v)

Microphone Characteristics• Transient response

– ability to respond to rapidly changing sound wave (“it’s all about physics”)

– diaphragm assembly of a dynamic microphone may weigh up to 1000x that of a condenser microphonea condenser microphone

Microphone Characteristics• Frequency response

– smoothness of frequency response curve– may be “flat” (“extended”) or “shaped”

Pickup Patterns• Omnidirectional

Pickup Patterns• Cardioid (“heart shaped”)

Pickup Patterns• Supercardioid

Pickup Patterns• Maximizing rear rejection

Directional Characteristics• ambient sound rejection (better with directional

microphones than non-directional)• distance factor (directional microphones have

greater “reach”)• off-axis coloration (less with non-directional

microphones)• proximity effect (bass boost on directional • proximity effect (bass boost on directional

microphones with decreasing distance)• susceptibility to “popping” (inherent in all directio nal

microphones)

Balanced Lines• electrical output of microphones is only a

few millivolts• to reduce noise susceptibility, use shielded,

balanced lines ONLY• braided shield is generally better at EMI

rejection than foil shieldrejection than foil shield

Musical Instruments• need to be aware of frequency range

(including harmonics) and directional output

Effects and Rules• multi-mic comb filtering

Effects and Rules• reflection comb filtering

Effects and Rules• 3-to-1 rule (“the distance between

microphones should be at least 3x the distance from each microphone to its intended sound source”)

Effects and Rules• General

– microphone technique boils down to personal taste (“whatever sounds right isright”)

– there is no one ideal microphone to use on any particular instrument (but there are any particular instrument (but there are “good choices” and “bad choices”)

– use as few microphones as are necessary to get a good sound (remember that every time the number of open microphones doubles, the potential acoustic gain decreases by 3 dB)

Live Microphone Techniques

Live Microphone Techniques

Live Microphone Techniques

Live Microphone Techniques

Live Microphone Techniques

Live Microphone Techniques

Live Microphone Techniques

Live Microphone Techniques

Let’s Play…What’s the Difference?

FM Wireless Systems• Basically a low -power transmitter and radio

receiver combination• Can be VHF/UHF, fixed -frequency or

frequency agile (tunable)

Wireless Frequency Bands

FM Intermodulation Effects

Two Transmitters Three Transmitters

FM Wireless Systems• Desirable characteristics

– UHF less prone to interference than VHF– diversity (dual antenna) receivers less

prone to signal dropout due to interference effects

– frequency synthesis provides tuning – frequency synthesis provides tuning flexibility

– squelch provides protection against noise bursts if signal drops out – “tone-key” preferable

– compatibility groups provide interference-free operation of multiple transmitters/receivers in same venue

FM Diversity Principle

FM Antenna Types

Transmitter

Receiver

Let’s Play…What’s the Difference?

Spread Spectrum Wireless

Outline – Racks and Wiring • Equipment Racks• Rack Issues• Rack Design Software• Sample Rack Layout and Equipment List• Wiring Issues• Wiring Issues

Equipment Rackshttp://www.middleatlantic.com/

http://www.racktools.com/

Rack Issues

• Access (installation and maintenance)• Mechanical support and stability• Ventilation• Cable routing and dressing• Cable routing and dressing

http://www.racktools.com/

Active Crossover (AC22)

Video RF Modulator

Reference Monitor GRQ (M7 & M8)

D-Zone 2 & 3 EQ (ME30)

Main Distribution Amp (DA-2)

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D-Zone Delay (ART PD3)

Choir & Balc Fill GRQ (Aux 5 & DA 3)

Hot Spot Monitor GRQ (Aux Send 1,2)

Floor Monitor GRQ (Aux Send 3,4)

Sanctuary & Chapel GRQ (DA 1 & 2)

D-Zone & Hear Ast Comp/Lim (dbx-C/L)

D-Zone 1 & Chapel Fill EQ (ME15B)

70V Distrib Amp (P912)

System Power Sequencer

Active Crossover (AC22)

Video RF Modulator

Reference Monitor GRQ (M7 & M8)

D-Zone 2 & 3 EQ (ME30)

Main Distribution Amp (DA-2)

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D-Zone Delay (ART PD3)

Choir & Balc Fill GRQ (Aux 5 & DA 3)

Hot Spot Monitor GRQ (Aux Send 1,2)

Floor Monitor GRQ (Aux Send 3,4)

Sanctuary & Chapel GRQ (DA 1 & 2)

D-Zone & Hear Ast Comp/Lim (dbx-C/L)

D-Zone 1 & Chapel Fill EQ (ME15B)

70V Distrib Amp (P912)

System Power Sequencer CD Recorder (CDW-33)

CD Player / Cassette Player Combo

System Power Control

CD Recorder (CDW-33)

CD Player / Cassette Player Combo

System Power Control

37U System Rack

24U Console Rack

Protected by locking plexiglass16 U security door

Sample Rack Layout

Sanctuary HF/LF Amp (MT1200)

Chapel HF/LF Amp (MT600)

Floor Mon 1/2 Amp (MT600)

Hot Spot 1/2 Amp (MT600)

D-Zone 2/3 Amp (MT600)

D-Zone 1/Choir Amp (CT400)

Balcony Fill/Chapel Fill (JBL)

<3U Drawer>

Amp Status Monitor

Sanctuary HF/LF Amp (MT1200)

Chapel HF/LF Amp (MT600)

Floor Mon 1/2 Amp (MT600)

Hot Spot 1/2 Amp (MT600)

D-Zone 2/3 Amp (MT600)

D-Zone 1/Choir Amp (CT400)

Balcony Fill/Chapel Fill (JBL)

<3U Drawer>

Amp Status Monitor

UHF Distribution Amp (UA844)

UHF Distribution Amp (UA844)

Dual UHF Wireless Receiver (ULXP4D)

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Effects Processor (Lexicon)

Dual UHF Wireless Receiver (ULXP4D)

Mixing Console Power Supply

UHF Distribution Amp (UA844)

UHF Distribution Amp (UA844)

Dual UHF Wireless Receiver (ULXP4D)

Dual UHF Wireless Receiver (ULXP4D)

Dual UHF Wireless Receiver (ULXP4D)

Dual UHF Wireless Receiver (ULXP4D)

Record C/L (dBX)

Dual Cassette Recorder (322-II)

UHF Distribution Amp (UA844)

UHF Distribution Amp (UA844)

Dual UHF Wireless Receiver (ULXP4D)

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Effects Processor (Lexicon)

Dual UHF Wireless Receiver (ULXP4D)

Mixing Console Power Supply

UHF Distribution Amp (UA844)

UHF Distribution Amp (UA844)

Dual UHF Wireless Receiver (ULXP4D)

Dual UHF Wireless Receiver (ULXP4D)

Dual UHF Wireless Receiver (ULXP4D)

Dual UHF Wireless Receiver (ULXP4D)

Record C/L (dBX)

Dual Cassette Recorder (322-II)

for maxed out wireless config = 8 HH + 4 BP

Sample Equipment List

Wiring Issues

• Power conditioning, distribution, and sequencing

• Balanced vs. unbalanced audio cables• XLR vs TRS connectors• XLR vs TRS connectors• Avoiding ground loops, hum, and buzz

A1 A2 A3 A4 A5 A6 A7-A10 M1 M2 M3 M4 M5 M6 M7 M8

GRQ3102

MT600

GRQ3102

MT600

Snake

ReturnsGRQ3102

½ dBX

DA-2

M2500-48

Mic 1-8 Mic 9-16 Mic 17-24 Mic 25-32 Mic 33-40 Mic 41-48 St 1 St 2 St 3 St 4

Cass

Player

Effects

Return

Computer/

Aux

Sample Signal Path Wiring Diagram

Ref MonRec Feeds

Lexicon

St 3

8-Wide “Patch Snakes” CD

Player

dBX C/L

GROUPS:1,2 - Acoustic Instruments3,4 - Electronic Instruments5,6 - Vocalists7,8 - ChoirC - Speaking (Wireless and Podium)

MATRIX:M1 - Main Distribution Amp

M5,6 - Stereo Record MixM7,8 - Reference Monitor

Hot Spot

MonitorsFloor

Monitors

CT400

Choir

Monitors

GRQ3102

AC22

MT1200

Sb121 EVI-28X2 X2Sanctuary

MT600

Sb121 Sx300

Chapel

GRQ3102

Under-

Balcony

D-Zone

ART PD3

MT600

Hospitality

D-Zones

P912

70 V Distrib

AUX Sends:

A1,2 - Hot Spot Monitor

A3,4 - Floor Monitor

A5 - Choir Monitor

A6 - Effects Send

A7-10 - Snake Returns

½ ME15+ ME30

Balcony

Fill

HAT

½ dBX½ ME15

JBL

Chapel

Fill

RF-Mod

Video

Feed

Video

Switcher

Power Sequence Control

Grounding Strategies

Grounding and Shielding Notes (Rane)

What’s in the “?” – Passive Schemes for Connecting Signal Ground to Chassis

Grounding and Shielding Notes (Rane)

Star Ground Scheme for Connecting Signal Ground to Chassis

Grounding and Shielding Notes (Rane)

Recommended Practice

Sound System Interconnection (Rane)

Recommended Practice – Unbalanced to Balanced Using Transformer Isolation

Sound System Interconnection (Rane)

Lots of Other Possibilities…

Sound System Interconnection (Rane)