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FUMC Sound Tech Course Session 3 Microphones, Speakers & Spkr Systems, Amplifiers This is a BLOCK DIAGRAM Handheld/Vocal Close range for individual singer/speaker UniDirectional - Cardioid or Hypercardioid pattern Feedback rejection Lavalier Close range Omni or Cardioid pattern Small

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fumc sound tech course session 3

FUMC Sound Tech CourseSession 3

Microphones, Speakers & Spkr Systems, Amplifiers

slide2

This is a

BLOCK DIAGRAM

microphone types
Handheld/Vocal

Close range for individual singer/speaker

UniDirectional - Cardioid or Hypercardioid pattern

Feedback rejection

Lavalier

Close range

Omni or Cardioid pattern

Small

Stand/Drop Mounted

Group pickup

Longer range

Recording (high quality)

Cardioid pattern

Over-the-Ear

Pastors, Speakers

Noise & Feedback rejection

Contact

Guitar, Piano

Pressure Response

Boundary mic

Shotgun

Long range

Noise cancelling

High noise environments

Actually 2 mics – out of phase

Microphone Types
transducer types
Transducer Types
  • Dynamic
    • Made like miniature speaker w/ coil & magnet
    • Warm response – Preferred by singers
  • Condenser
    • Made to form a capacitor (condenser)
    • Gold sputtered diaphragm acts as capacitor plate
    • Requires amplifier & voltage supply (phantom power)
    • Excellent frequency response
    • Small vs. Large Diaphragm
  • Electret condenser
    • Permanently charged diaphram
    • Small & cheap
transducer types continued
Transducer Types - Continued
  • Ribbon
    • Metal ribbon suspended between magnet poles
    • Flat frequency response - Great recording mics
    • Expensive
  • Carbon
    • Earliest type, used in telephones until recently
    • Carbon granules form resistance element
    • Poor frequency response but very rugged
  • Piezoelectric
      • Diaphragm connected to piezoelectric material
      • Cheap – low cost mics of a few years ago
      • Crystal or Ceramic mic
mic pickup patterns
Mic Pickup Patterns
  • Omnidirectional (Omni)
    • Equally sensitive in all directions
  • Cardioid (heart shaped)
    • Directional
    • Most popular
    • Very little pickup directly behind
  • Hypercardioid
      • Reduces side pickup
      • Has some pickup directly behind
  • Proximity effect
    • Bass boost when mic is very close to source
    • Only in directional mics (not omni)
important mic specs
Important Mic Specs
  • Sensitivity
    • Ex: -47dBv @ 94dB SPL
  • Maximum SPL (overload)
    • Ex: 140 dB SPL
  • Frequency Response
    • Ex: 50-15,000 Hz +/- 6dB
    • Look for response curve
  • Impedance
    • Low
      • Most Pro mics, < 150 Ohms
      • Tolerate long cable runs
      • Balanced output
    • High
      • Low Cost Piezo/crystal mics
      • 25,000 Ohms or greater
      • Unbalanced Cables up to 20 ft
wireless mics
Wireless Mics

System consists of:

  • FM Transmitter (Tx)
  • FM Receiver (Rx)
    • Best are Dual Diversity ( 2 separate receivers in the case w/ 2 antennas. Output auto switches to the Rx with best signal )
    • Best are UHF frequency range (500-900 MHz) – Less interference
    • Lower cost are VHF (150-200 MHz) – More crowded=More interference
    • Best are tunable frequency, otherwise are fixed frequency
  • Controls
    • Transmitter
      • On/Off, Mute, Frequency select, Mic Sensitivity
    • Receiver
      • Frequency Select, Audio Output level, Squelch level
      • Metering-RF signal strength, Audio level, Muting, Battery low
sennheiser wireless mics
Sennheiser Wireless Mics
  • FUMC uses Handheld & Lavalier styles
  • Operation
    • Handheld Mic - Push Red On/Off button for 2 sec & ONLY with fleshy part of your finger…..NOT the fingernail
    • Check Rx Signal Strength Meter…Should be Mid-to-Full Scale
    • Check Rx AF Meter…Should go up as you talk or tap mic
    • Check Rx MUTE Indicator if no audio out
    • Check that Rx & Tx are on the correct frequency
    • Check Tx Sensitivity if too much or not enough volume
    • Put in freshly charged NiMH batteries for use & put batteries back in Charger after use. Charged batts will run approx 8 hrs
    • We use 3 frequency bands: 500MHz, 600MHz & 700MHz. See the freq charts for each mic’s assigned frequency.
speakers
Speakers
  • Convert electrical sound signals back to Sound Waves
    • Electromagnetic Transducers
      • Fixed Magnet w/ Moving Coil
      • Large magnet = higher power
      • Semi-rigid cone w/ corrugated surround
    • Piezoelectric Transducers
      • High Frequency Drivers (Tweeters)
low frequency drivers
Low Frequency Drivers

Low frequencies require moving lots of air

  • Electromagnetic Transducer
    • Large Diaphragm Area
    • Long Diaphragm Excursion (Long Throw)
    • High power handling
      • Heavy Magnet structure
      • Large Diameter Voice Coil w/ large wire
      • Rigid frame
      • HEAVY!
high frequency drivers
High Frequency Drivers
  • Types
    • Cone, Dome, Piezoelectric, Horn
    • Short cone movement
    • Low power required
    • EASILY DAMAGED by high volumes, Amp clipping
  • Consumer speakers use Cone, Dome, Piezo HF Drivers
    • Provide as wide dispersion of sound as possible
  • Pro Speakers use Horn HF Drivers
    • Provide CONTROLLED dispersion of sound
    • Common units are 40V X 60H and 40V X 90H degrees

Typical Constant Directivity Horn

pro speakers cabinets
Pro Speakers (Cabinets)
  • 2 or 3 Drivers per cabinet
    • Called “2 Way” or “3 Way”
    • Low Frequency Driver (woofer)
    • Mid-Range Driver
    • Hi Frequency Driver (Horn)
  • Bass Reflex Cabinet
    • Box is “tuned” to LF Driver with Ports to extend low frequency response

Typical 2-Way Pro Speaker

crossovers
Crossovers
  • Separates out proper audio frequencies to send to each Driver
  • Passive (High level)
    • RLC network inside speaker cabinet
    • One Amplifier output wire pair drives entire cabinet
    • “Brute Force” method
    • Not most efficient
  • Active (Low level)
    • Electronic Crossover separates the various frequency bands
    • Separate Power Amplifiers for Low, Mid, High frequency Drivers
    • Multiple amp output wire pairs to speaker cabinet
    • Efficient
    • Used in Concert & Touring systems
crossover frequency response curves
Crossover Frequency Response Curves

Idealized 2-way crossover response

speaker specs
Speaker Specs
  • Frequency response
    • Ex: 60 – 15,000 Hz +/- 6dB
  • Impedance (nominal)
    • Ex: 8 Ohms, 4 Ohms
    • Most spkrs either 8 or 4 Ohms
  • Power Handling (Watts)
    • RMS = Constant sine wave
    • Program = Double RMS
    • Peak = 4 X RMS
speaker specs cont
Speaker Specs (cont)
  • Sensitivity
    • SPL output level with 1 watt input power (normally at 1 meter from Spkr)

Ex: Sensitivity = 95 dB (Sensitivities range from 85 dB to 100+ dB)

  • Example (using above speaker sensitivity)
    • What is SPL @ 1 meter with a 100 watt amplifier?
    • What is SPL @ 4 meters with a 100 watt amplifier?
    • What is SPL @ 16 meters with the 100 watt amplifier?
  • Speaker Beamwidth
    • Degrees (Horizontal & Vertical) vs. frequency
  • Maximum SPL Output
    • XX dB at rated input power (Ex: 125 dB @ 500 watts)
speaker system design
Speaker System Design
  • Use multiple speaker cabinets & Arrange in Arrays to provide the required room coverage
    • Direct sound at the audience, NOT at walls
      • Minimize sound reflections
    • Provide as constant SPL (& frequency response) as possible across room
    • Use Main cabinets in front and “fill” cabinets as necessary
    • Use Time Delay units to drive rear & fill cabinets to account for closer fill speaker placement
fumc speaker systems

All FUMC Venue speaker systems are 3-Way

    • Main Cabinets are 2-Way (low frequency driver covers 80-250 Hz + high frequency Horn covers 250-20KHz
        • Uses an internal Passive Crossover
    • Subwoofer Cabinet covers 80 Hz and lower
    • An Active (electronic) Crossover set to an 80 Hz frequency takes the Mixer output signal and sends 80 Hz and below to SubWoofer Amplifier and 80 Hz and above frequencies to Main Amplifier

FUMC Speaker Systems

Main Amp

Mixer

Electronic

(active)

Crossover

Passive X-Over

Sub Amp

Sub

monitor speakers wedges
Monitor Speakers (Wedges)
  • Allow singers & bandsmen to hear music & themselves
    • Usually on stage in front of performer (aimed at performer)
    • Mix is different from main House mix
microphone stand etiquette
Microphone Stand Etiquette
  • Fold out legs
  • RELEASE Tension knob before moving boom
    • Stand will be RUINED if boom joint is forced
power amplifiers
Power Amplifiers
  • Convert low audio voltage/high impedance levels to high voltage/low impedance to drive speakers
    • Input: +4dBV @ 600 Ohms
    • Output: 100-400V @ 8/4/2 Ohms
    • High Current output
  • Final component in the chain, just before speakers
  • Internal Components
    • Power Supply
      • Transformer / Rectifier / Series Regulator
      • High frequency chopper
    • Input amplifier stage
    • Power amplifier stage
    • Protection circuits (clip/overload protection)
power amplifier specs
Power Amplifier Specs
  • Frequency Response
    • Frequency range passed by the device
    • Ex: 20-20,000 Hz +/- 2 dB
  • Power Bandwidth
    • Frequency range over which the amp puts out at least ½ its rated power

Typical Power Bandwidths

power amp specs
Power Amp Specs
  • Power Output level
  • Output Impedance
    • Speaker impedances the amp will support
    • Usually 8 ohms, 4 ohms, or even 2 ohms
    • Output current required goes up with lower speaker impedance
    • Amp that will drive 2 ohm loads is top rung
power amp specs25
Power Amp Specs
  • Clipping
    • Pushing an amplifier beyond the limits of its output capability
    • Makes a sine wave into a square wave
      • Adds harmonic frequencies to original audio signal
      • Speaker damage!
power amp specs26
Power Amp Specs
  • Distortion
    • Output signal that was not identical to the input signal
    • Distortion ADDED to the “perfect” input signal
    • Total Harmonic Distortion (THD)
      • Ex: 100 watts @.05% THD
    • Intermodulation Distortion (IM)
      • Non-linear mixing of 2 audio frequencies
power amp output modes
Power Amp Output Modes
  • Stereo
    • 2 Channels driven with different signals – 2 outputs
  • Mono (Parallel)
    • 2 Channels driven with same signal – 2 outputs
  • Bridge
    • 2 Channels driven with same signal – 1 output
    • Maximizes power output of amp
    • Channels are fed inputs out of phase so channels add power
    • Minimum output impedance is doubled
      • 2 Ohm minimum in Stereo or Mono becomes 4 Ohm minimum in Bridge mode
multiple speakers
Multiple Speakers

Total Impedance = Z1 + Z2 + Z3

Total Impedance =

1

1/Z1 + 1/Z2 + 1/Z3

Examples:

2ea 8 Ohm speakers in Parallel = 4 Ohms

3ea 8 Ohm speakers in Parallel = 2.7 Ohms

4ea 8 Ohm speakers in Parallel = 2 Ohms

audio equipment measurements of interest
Audio Equipment Measurementsof Interest
  • Power: Watts = Amps x Volts
  • Resistance: Ohms, Kilohms, Megohms
  • Impedance: “Complex Resistance”
    • Similar to Resistance
    • Ohms
  • Voltage: Volts, Millivolts, Microvolts
  • Current: Amps, Milliamps (1/1000 amp)
slide30

Ohms Law

  • I = V / R (Current = Voltage / Resistance)
    • Other forms are also valid
      • R = V / I
      • V = I x R
      • E is often used instead of V (for voltage)
        • I=E/R
  • Power = I x V = V² / R = I² x R
guess the frequency game
Guess the Frequency Game
  • Important that you can pick out frequency content so you can EQ properly.
    • Choices:
      • 50 Hz
      • 100 Hz
      • 315 Hz
      • 1000 Hz
      • 2 KHz
      • 3.15 KHz
      • 6.3 KHz
      • 10KHz