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BASIC SOUND REINFORCEMENT - PowerPoint

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BASIC SOUND REINFORCEMENT - PowerPoint Powered By Docstoc
					                                            According to Dale Shelton
Portions of this material were gleaned from the following sources and used with their permission:
                                Peavey Advanced Sound Reinforcement Seminar, Peavey Corporation,
                                                                       (Thanks to Marty McCann)
                                                                 Rane Technical Notes, Rane Corp,
                                                                         (Thanks to Dennis Bohn)
            Sound and Light Team (SALT) Training Manual, Advent Lutheran Church, Boca Raton, FL
                                                                            (Thanks to Ken Ellis)
       COURSE OBJECTIVES
•   Create a Team of Transparent Sound Techs
•   Basic Math and Electronics
•   Nature of Sound
•   Electronic Domain
•   Propagation
•   Components of a System
•   Interconnection
•   Soldering & Cable Fab
•   Other Communications Systems
     Transparent Sound Techs
• Pray about it!
  – Pray before each event that you glorify God
• Have a servant’s heart
  – NEVER upset the Pastor or any performer
    before the service or program
• Get the training you need


                        Pray without ceasing. - 1 Thessalonians 5:17
     Transparent Sound Techs
• Work as a Team
  – Support, help, and encourage each other
  – Give and accept criticism gracefully
• Help the performer be comfortable
  – Not be distracted by the sound system
  – OR Sound Technician
• SMILE (it really does make a difference)
                     A cheerful look brings joy to the heart, and good
                     news gives health to the bones. - Proverbs 15:30
       Transparent Sound Techs
• Never become the focus of the audience
• The system should realistically reproduce
  sounds as they occur
  –   Sounds should be natural
  –   Sounds should be clear
  –   Quiet sounds should be audible throughout
  –   Loud sounds should not be too loud

                        If it is possible, as far as it depends on you, live
                                   at peace with everyone. - Romans 12:3
     Transparent Sound Techs
• Give out a complement or word of
  encouragement now and then
• Be prepared well before the program starts
  – Check-out the sound system before performance
  – Check mics, instrument, monitor levels, and
    queue tapes
  – Obtain a sequence of events or script

                      A hot-tempered man stirs up dissension, but a
                      patient man calms a quarrel. Proverbs 15:18
     Transparent Sound Techs
• NEVER antagonize the performers!
• Pay attention during the entire service
  – Don’t allow yourself to be distracted
  – Take your service seriously
  – If someone picks up the wrong mike, make sure
    you are there to turn it on.
  – Listen to the program & make needed
    adjustments
                    A fool gives full vent to his anger, but a wise man
                       keeps himself under control. - Proverbs 29:11
      Transparent Sound Techs
• Pay attention during the entire service cont...
  – Be prepared for unexpected changes. If the
    performer moves to an area that is not lit, make
    sure you are there to adjust the lighting (if
    applicable)
• Strike the system
  – Neatly stow the equipment after the event
  – Take good care of God’s equipment
                      Everything devoted is holy to the highest degree;
                           it's God's inalienable property. – Lev 27:28
   Basic Math and Electronics
• Terms:
  –   Voltage (E)
  –   Current (I)
  –   Resistance (R)
  –   Power (P)
  –   Impedance
  –   Inductance
  –   Capacitance
     Basic Math and Electronics
• Voltage is the unit of measurement for
  electricity and it is analogous to electrical
  pressure or the potential to perform work.
• Voltage is sometimes referred to as emf or
  electromotive force.
     Basic Math and Electronics
• Current is the rate or number of electrons
  that flow past a given point in an electrical
  circuit and is measured in amperes.
  – Direct current flow (DC) occurs when the
    electrons flowing in an electrical circuit path
    move in one direction only
  – Alternating current flow (AC) occurs when the
    electrons flowing in an electrical circuit path
    continuously change directions.
     Basic Math and Electronics
• Resistance is the opposition to DC electron
  flow and is measured in ohms.
• Impedance is the opposition to AC electron
  flow and is measured in ohms.
  – Varies with frequency and the capacitance or
    inductance of the electrical circuit.
    Basic Math and Electronics

• Ohm’s Law: An electromotive pressure of
  one volt in a electrical circuit with one ohm
  of resistance will result in one ampere of
  current flow and one watt of power.
     Basic Math and Electronics


• Inductance is that property in a circuit that
  offers high opposition to current flow at
  high frequencies.
  – An inductor is a coil of wire that offers high
    opposition to current flow at high frequencies
    and low opposition to current flow at low
    frequencies.
    Basic Math and Electronics

• Capacitance is that property in an electrical
  circuit that offers high opposition to current
  flow at low frequencies.
  – A capacitor consists of two electrical plates or
    conductors separated by a dielectric or something
    that will support an electrical charge.
  – A capacitor offers high opposition to low
    frequency current flow and low opposition to high
    frequency current flow.
   Basic Math and Electronics

• Power in watts is equal to the voltage squared
  divided by the resistance of the load.

 402 = 40 x 40 / 4 = 1600 / 4 = 400 watts
  4

• Power equals current times voltage.
      40v x 40Amps = 1600 watts
      Basic Math and Electronics
        40 v


               Amplifier

Amplifier          Resistor
  “rail”       (Speaker in our   Ground
 voltage         application)
Basic Math and Electronics
                8 ohm
 40 v


               ? Watts

   40 V x 40 V / 8 ohm
        = 1600 / 8
        = 200 W
Basic Math and Electronics
                4 ohm
 40 v


               ? Watts
    40 V x 40 V / 4 ohm
         = 1600 / 4
         = 400 W
Basic Math and Electronics
  40 V             4 ohm


    ______ W    _____ A

                8 ohm
   40 v

          _____ W _____ A
Basic Math and Electronics

            8 ohm

 40 V
            8 ohm


        ______ W    ______ A
Basic Math and Electronics
                  8 ohm


                  8 ohm

    40 V
                  8 ohm


                  8 ohm




       ______ W    ______ A
Basic Math and Electronics

        8 ohm            8 ohm

 40 V

        8 ohm            8 ohm



           _______ W   ______ A
        Basic Math and Electronics
    • Logarithmic Scale
       – Easy way to represent huge and complex
         numbers
    1000000 100000 10000 1000 100 10 1
      106     105     104     103 102 101 100
Log(1000000) = 6            Log(100) = 2
  Log(100000) = 5               Log(10) = 1
          Log(10000) = 4
                    Log(1000) = 3     Log(1) = 0
      Basic Math and Electronics
• Logarithmic Scale
  –   10
  –   100000
  –   871291812
  –   11298
            Basic deciBels

• The Decibel Scale involves changes in the
  electrical gain (volume), or the amplification
  of the audio signal, that results in changes in
  the intensity of the Sound Pressure Level
  (SPL), perceived by the listener.
• Gain changes in dB and the resultant changes
  in system power and voltage to the
  loudspeaker:
                    Decibels dB
Changes in:
           Audible
Decibel Perception       Power     Voltage
+ dB Just Noticeable       Times       %

+   dB   Moderate          Times      %

+   dB   Twice as Loud     Times       %
                    Decibels dB
Changes in:
           Audible
Decibel Perception       Power      Voltage
 +3 dB Just Noticeable   2 Times     40%

 +6 dB   Moderate        4 Times    100%

+10 dB   Twice as Loud   10 Times   300%
     dB Examples in Specifications
Loudspeaker Frequency Response: 50 Hz - 17.5 kHz +/- 3 dB
Power Amplifier Frequency Response: 10 Hz - 20 kHz +/- 0.5 dB
Common Mode Rejection Ratio: -100dB
Equivalent Input Noise: -129 dB
Equalization or Tone Control Range of Boost & Cut: +/- 15 dB
Signal to Noise: -105 dB
Crossover Slope: -24 dB/Octave
Amplifier Gain: 30 dB
Power Amp Sensitivity: 1.4 dB
Loudspeaker 1 Watt 1 Meter Sensitivity: 101 dB
Dynamic Range: 120 dB
0 dBv = 1 volt
0 dBm = 0.77456 volts
The Decibels’ most Important use in
         System Design

 • The Inverse Square Law
 • High Frequency CD Horn -6 dB
   Patterns of Coverage
      Inverse Square Law:
• The sound eminating directly from a
  source will change in sound pressure
  level (SPL), directly proportional to the
  inverse of the square of the distance
  away from the source.
  – Sound drops 6 db in level (SPL) each
    time you double the distance away from
    the source.
      Inverse Square Law:

AREA OF A CIRCLE:
 = Radius Squared x Pi

AREA OF 1/2 CIRCLE:
 = 1/2 Radius Squared x Pi
          Circle

Radius      Area
 4 ft =      25.13 ft2
 8 ft =     100.53 ft2
16 ft =     402.12 ft2

32 ft   = 1,608.49 ft2
              Sphere
Volume Of A Sphere:
 = 4R2p

Volume Of 1/2 A Sphere:
 = 2R2p
         Area Of 1/2 Sphere
Radius          Area
 4 ft     =     100.53   ft3
 8 ft     =     402.12   ft3
16 ft     =   1,608.49   ft3
32 ft     =   6,433.98   ft3
             Nature of Sound
• Introduction to Sound Reinforcement
  –   Sound as Vibrations
  –   of Air Molecules (VPS)
  –   Musical Sound + Speech Sound = Audio
  –   Electronic Audio Signals
  –   Frequency and Hertz (CPS & Hz)
           Nature of Sound
• Introduction to Basic Decibels
  – Human Auditory Perception and the Decibel Scale
  – Rules of Thumb for the Decibel
  – 30 Volt 100 Hz sound wave verses an unknown
    sound wave
  – Dr. Flecther & Dr. Munson - Perception in
    decibels
             Nature of Sound
                           Frequency     Wave Length
• Velocity
                              160   Hz    7.1   Ft
  – Common value is 1132      320   Hz    3.5   Ft
    Feet Per Second
                              640   Hz    1.8   Ft
• Wavelength                 1280   Hz    0.9   Ft
  l=    Velocity
        Frequency
                             2560   Hz    0.4   Ft
                             5120   Hz    0.2   Ft
                            10240   Hz    0.1   Ft
                            20480   Hz    0.1   Ft
                            40960   Hz    0.0   Ft
                            81920   Hz    0.0   Ft
             Nature of Sound
• Sound Pressure
  – Force exerted by a sound wave
  – Sound pressure is measured in
    N/m2.
  – The logarithmic response of the
    ear makes it useful to map
    decibel value
                             p
      20log10(               p0       )dB
             Nature of Sound
• 0dBA The threshold of audibility
  – A reference value must be used
     • p0
     • Lowest sound level which can be heard by the
       human ear is 2x10-5 N/m2, the Internationally agreed
       level for p0. This is the value which represents 0dBA
       (deciBels Acoustic).
      Nature of Sound
Description                  Sound      dBA
                           Pressure
                               N/m2
Threshold of Feeling            63.2    130
Large jet aircraft (40m)          20    120
Large orchestra (5m)              6.3   110
Tube Train passing                2.0   100
Inside Tube Train               0.63    90
Noisy Office                      0.2   80
Conversational speech          0.063    70
Reading From a Book (1m)        0.02    60
Average Office              6.3x10-3    50
Quiet Office                  2x10-3    40
Public Library              6.3x10-4    30
Whisper (2m)                  2x10-4    20
Quiet Whisper (1m)          6.3x10-5    10
Threshold of audibility       2x10-5    0
             Nature of Sound
• Acoustical Properties of Sound
  Velocity
  Wavelength
  Sound Fields
      Free Field
      Direct Field
      In-Direct Field
      Reverberant Field
  Critical Distance
            Nature of Sound
• Time Delay Calculations
  – Delay is required if the sound paths to a point
    differ by a period of more than 40 ms (40 ft at
    14°C).
  – To maintain the directionality of the implied
    source the "direct" sound should arrive first
    (Hass Effect).
            Nature of Sound
• Acoustical Properties of Sound
  – Propagation of Sound Waves
     • Omni-Directional
     • Hemi-Spherical
     • Conical
              Nature of Sound
• Acoustical Properties of Rooms
  Finding Critical Distance   Absorption
  Reflections                 Diaphragmatic Absorption
  Standing Waves              Diffraction
  Room Modes                  Diffusion
  Boundary Cancellation       Room Treatment
             Nature of Sound
• Acoustical Properties of Rooms
  – Reverberation Time
     • Formula developed by W.C.Sabin, 19th century
     • Unit is a measures absorption from 0 to 1
        – Adsorption coefficient of 0 indicates a material that
          reflects sound totally
        – Coefficient of 1, a material that adsorbs sound totally
             Nature of Sound
• Acoustical Properties of Rooms
  – Sabin’s Formula
     • Rt      = Reverberation time
     • VR      = Volume of the room in m3
     • S1...Sn = The Sabin coefficient for a particular material
     • A1...An = Surface area of the material in the room in m2
     • Sa      = The Sabin coefficient of air
                           0.16VR
      Rt       =
                     (S1A1) … (SnA) + (SaVR)
             Nature of Sound
• Acoustical Properties of Rooms
  – Sabin’s Formula cont...
    Typical Absorption Coefficients
                                  250    500   1000
                                   Hz     Hz     Hz
    Brickwork                    0.04   0.02   0.04
    Concrete                     0.02   0.02   0.04
    Plaster - Solid backing      0.03   0.02   0.03
    Carpet - Thick pile          0.25   0.05   0.05
    Air - per m3                 0      0      0.003
    Audience in Upholstered Seat 0.04   0.46   0.46
    Wooden Seat - Empty          0      0.15   0
    Rostrum                      0.1    0      0
                 Nature of Sound
• Sound Insulation
4" (100 mm) brick, plastered both sides                       40 dB
9" (230 mm) brick plastered both sides                        52 dB
4" brick walls with 2" (50 mm) cavity, plastered both sides   56 dB
6" (150 mm) concrete block wall, solid and plastered          50 dB
3/8" gypsum wall board                                        26 dB
1/2" gypsum wall board                                        28 dB
5/8" gypsum wall board                                        31 dB
Partition of 3/8" plastered gypsum wall board with 4"
                                                              43 dB
cavity
            Nature of Sound
• Loudspeaker Q
  – A measure of a loudspeakers "throw”
  – Calculated from the horizontal and vertical
    beam angles measured at 6 dB down point
  – Loudspeakers with a very wide beam will have
    a low Q and those with a narrow beam will
    have a high Q
          Nature of Sound

                           180
Q=                     sin(AH)sin(AV)
              –1
        sin        (          4         )
– AH = Horizontal beam angle in degrees
– AV = Vertical beam angle in degrees
 SPEAKER TYPE                HORIZ   VERT   Q
 Mid/Low Frequency Unit      180     180    2
 Line Source Column          180     40     9
 HF Horn                     40      40     26
             Nature of Sound
• Articulation Loss
  – Most vocal clarity is contained in consonants.
  – Early research with telephone systems indicated
    that if 15% or more of the consonants were lost
    the speech intelligibility would be poor
  – The main cause of this mussying of the sound is
    the interaction of the direct sound (from the
    loudspeaker) and the reverberated sound.
     • Monitors set too loud are reverberant when heard in
       front of house
               Nature of Sound
• Articulation Loss
                       200d2Rt2(n+1)
              %Acons =
                          VRMQ
%Alcons = The percentage of lost consonants
d        = The distance from the loudspeaker to the furthest
         member of the audience
Rt       = Reverberation time
n        = The number of loudspeaker groups
VR       = Volume of the room in m3
Q        = The Q of the loudspeaker groups
M        = Usually 1, more accurate M=(1 - average absorption
         coefficient of the room) x (1 - average absorption
         coefficient of the area covered by the loudspeaker)
         Nature of Sound
• Constant Directivity Horns’ angle of
  coverage are determined by the -6 dB
  down points of the horn in the
  Horizontal and Vertical planes.
• The angles of coverage are the points
  that measure -6 dB less than the on-
  axis measurement.
                              Nature of Sound
          • Place speaker(s) to achieve a barely
            perceptible change in volume (±3dB)

          100 dB on
          axis at 1
          meter
 6.5 Ft
                                        52.9 Ft
7 Degrees    96 dB    13 Ft

                       11.5 Ft                             52.5 Ft   65.9 Ft
                       81.9 dB                             75.8 dB

                              11.5 - 52.5 Feet = +/- 3dB
Nature of Sound
            Electronic Domain
• The Electronic Audio Signal Domain
  –   Voltage
  –   Current
  –   Resistance
  –   AC Impedance
  –   Power
  –   Ohm's Law
  –   Calculating Power Output
  –   D D T / Compression
           Electronic Domain
• Amplification in General
  –   Electrical Gain
  –   Power Supply DC Voltage Rails
  –   Clipping
  –   Headroom
  –   General Gain Stages
           Electronic Domain
• Amplification is the increase in electrical level
  (Gain) of a signal.
• The microphone’s signal level is increased by the
  subsequent gain stages of the audio system.
• Amplification occurs because within any gain
  stage is a Power Supply that allows the signal to
  pass through a Positive and Negative voltage
  window.
• The audio signal is said to swing between the two
  (+/-) voltage rails of the amplifier stage.
               Electronic Domain
• The maximum positive and negative voltage swing
  available are refered to as the “voltage rails” or limits.
• When the signal reaches either voltage rail it is said to
  Clip.
• Amplifier clipping is the most common cause of
  distortion.
• Headroom is defined as the difference between the
  average signal voltage level and the maximum level at
  clipping.
Electronic Domain

     CLIPPING




      } HEADROOM
             Electronic Domain
• Signal Flow
  – General Identification and Sequential
    Placement of Components:
     •   Microphones / Sources
     •   Pre Amp / Noise-Gate / Limiter / Feed-Back / Mixer
     •   Signal Processors
     •   Power Amplifiers
     •   Loudspeakers
           Electronic Domain
• Signal Flow cont...
  –   Operating Levels
  –   Component Hookup
  –   Unbalanced & Balanced Cable
  –   Loudspeaker Cable
            Electronic Domain
• Microphones
  – Types:
    •   Pressure Gradient
    •   Velocity
    •   Dynamic
    •   Neo-Dynamic
    •   Condenser and Electret Condenser
    •   Ribbon
    •   Boundary
           Electronic Domain
• Microphones cont...
  –   Pick-up Patterns
  –   Proximity Effect
  –   Microphone Placement Applications
  –   Polarity
Microphones Application
 Hands-On Workshop
           Electronic Domain
• Mixers
  Balanced Inputs          Passive EQ
  Line Inputs              Shelving EQ
  Pre Amp \ Input Gain     Peaking / Dipping,
  Channel Patch \ Insert   Boost / Cut
  Monitor Sends            Paramid
  Types of Equalization:   Parametric EQ
  Active EQ                Effects Sends Aux Sends
           Electronic Domain
• Balanced Lines
  –   EMI - Electro-Magnetic Interference
  –   CMRR - Common Mode Rejection Ratio
  –   Electronic Balanced Inputs
  –   Transformer Balanced Inputs
  –   Balanced Outputs
  –   Ground Loops and Pin 1 Lift
            Electronic Domain
• 70 Volt Distributed-Line Systems
  –   High Current Signal Loss
  –   Step-up Transformers
  –   70 Volt via Bridge Mode
  –   Line Matching Transformers
  –   Selecting Input & Output Taps
  –   Calculating SPL
            Electronic Domain
• Electrical Power Distribution
  –   Electrical Safety
  –   NEC - National Electrical Code
  –   120VAC 60 Hz Single Phase
  –   U.S. Commercial Electrical Distribution
  –   Large System and Ground Loops
  –   A Studio Performance Solution to Ground
      Loops
            Electronic Domain
• Power Amplifiers
  –   Specification Definitions:
  –   Sensitivity
  –   Output Power
  –   Minimum Load Impedance
  –   Current Limiting
  –   Headroom
            Electronic Domain
• Power Amplifiers
  –   Dynamic Headroom
  –   “DDT”
  –   Signal to Noise Ratios
  –   Frequency Response
  –   Total Harmonic Distortion
           Electronic Domain
• Power Amplifiers
  –   Damping Factor
  –   Slew Rate
  –   Amplifier Classes
  –   Power Consumption
  –   Power Amplifier AB Comparison
          Electronic Domain
• Is is possible to get 400 watts from a 280
  watt amplifier?
  – RMS volts = .707 X Pk to Pk
  – Sine wave is at right            40 volts
  – Root Mean Squared is
    the power under the curve



                                     0 volts
          Electronic Domain
• Is is possible to get 400 watts from a 280
  watt amplifier?
  – The power, shown in
    blue is what drives
    the voltage up
  – Assuming 40VDC
    power supply rails, we have
    40 * .707 = 28.28 VAC(or RMS)
          Electronic Domain
• Is is possible to get 400 watts from a 280
  watt amplifier?
  – Assuming our power
    supply is 10 amps,
    pwr = Volts * amps
    so:

    282.2 watts = 28.28VAC * 10A
          Electronic Domain
• Is is possible to get 400 watts from a 280
  watt amplifier?
  – HOWEVER:
    If we drive the signal
    to clipping, the area
    under the curve
    gets a LOT larger.
          Electronic Domain
• Is is possible to get 400 watts from a 280
  watt amplifier?
  – Computing the area
    under a square wave
    is easier, no need
    for trigonometric conversion,
    it’s equal to the rail voltage
          Electronic Domain
• Is is possible to get 400 watts from a 280
  watt amplifier?
  YES!
  – VAC = 40
          SO
    400pwr = 40VAC * 10A
• CLIPPING IS BAD
  – Especially for speakers
           Electronic Domain
• Loudspeaker Transducer Technology
  – Basic Construction
  – Loudspeaker Enclosure Types
    •   Direct Radiators
    •   Infinite Baffled
    •   Vented Boxes Horn Loaded
    •   Straight Horn
    •   Folded Horn & Vented Horn
    •   Resonant Bass Systems
            Electronic Domain
• High Frequency Horns & Compression Drivers
  –   Why We Need Them
  –   How They Work
  –   Motor Structure
  –   Phasing Plug
  –   Cut-Off Frequency
  –   Exponential Radial Horns
  –   Constant Directivity Horns
           Electronic Domain
• Constant Directivity Horn Equalization
  –   Driver Mid-Band Sensitivity
  –   High Frequency Roll-Off
  –   High Frequency Compensation
  –   Passive Crossovers
  –   Active Crossovers
                 Propagation
• Decibels and Sound Engineering
  –   The Inverse Square Law
  –   Loudspeaker Sensitivity
  –   Logarithm Decibel Calculations
  –   Power = 10 x Log
  –   Distance, SPL, Voltage, & Current = 20 x Log
                Propagation
• Loudspeaker Placement
  –   Room Considerations
  –   Importance of Aiming the High Frequency Horns
  –   Don’t Overlap Constant Directivity Horns
  –   Trapezoidal Box Considerations
  –   Mutual Coupling
  –   Woofer Arrays
                Propagation
• Loudspeaker Placement
  –   Horizontal Coverage
  –   Near and Far Field Coverage
  –   Cost Effective Bridged Array
  –   Delayed Loudspeaker Systems
  –   0.9 Feet per millisecond
  –   The Haas Effect
               Propagation
• Bi-amping & Triamping Sound Systems
  – Dr.’s Fletcher and Munson Revisited
  – Composite Waveform of Low & High
    Frequency (100 Hz/1000 Hz)
  – Demonstration of a Bi-amped versus a Full
    Range Speaker System
Components of a System
Interconnection
Soldering & Cable Fab
Other Communications Systems
• Typical Components
  –   RJ-11
  –   RJ-45
  –   66 Block
  –   110 Block
  –   Cat V
  –   Hub
  –   Tools
                 Summary
•   Create a Team of Transparent Sound Techs
•   Nature of Sound
•   Electronic Domain
•   Propagation
•   Components of a System
•   Interconnection
•   Soldering & Cable Fab
•   Other Communications Systems

				
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