Buying the right PA for your band and building

Glyn Chapman

Acoustic Arrangements

Needs Analysis

• Who’s it for?• What’s it for?• Who’s going operate it?• What worship styles?• For now or for the future?• Plan for occasional needs.• What about video, lighting & electrics.• What best serves the vision of the Church.

The Sound System

Basic System

•Source

•Mixer

•Amplifier

•Loudspeaker

Inputs

• MicrophonesDynamic (moving coil)CondenserPick-Up PatternStyle

• DI Boxes (direct injection)Active/PassiveElectro-Acoustics, Keyboard, Bass

• Radio Mics, CD, DVD, PC

Cables, Connectors, Multicore

• Balanced Cable

Cables, Connectors, Multicore

• XLRpin 1 gnd, pin 2 +ve (hot), pin 3 -ve (cold)

• JACKTRS: tip, ring sleeve (stereo jack)as balanced: tip +ve, ring -ve, sleeve gnd

• To unbalance: link gnd & -ve

Cables, Connectors, Multicore

• Multicore: How many sends?How many returns?How long?

Mixer

• Analogue ‘v’ Digital

Number of inputs (channels)EQRouting: AuxiliariesPowered or Unpowered

Processors

• Effects: Reverb, Chorus, Delay• Compressor/Limiters• Gates

• Graphic Equalisers• Crossovers• Speaker Controllers

Amplifiers

• Constant Voltage 100v LineSpeaker load not exceed 75% of amp power.

• Low ImpedanceExample: 500w into 4ohm

= 300w into 8ohm = 700w into 2ohm

Allow for headroom up to twice speaker power

Speakers

• Power: RMS = ContinuousProgram = 2 x ContinuousPeak = 4 x Continuous

• Sensitivity: SPL – Sound Pressure LevelEx: 400w 96dB speaker is same level as 200w 99dB speakerI.e. you need twice the power for 3dB increase in level

• Add 2nd speaker adds 3dB or 6dB if placed together

Speakers

• Inverse Square Law: -6 dB per distance doubled

• Dispersion• Low Impedance/100v Line• Line Array• Horn Loaded

Speakers

Top Tips

• Listen to advice from professionals• Check your cables & connectors• Throw away old, broken or unusable kit• Use your ears• Check your mid range EQ• Don’t buy something just because it’s on

offer• Buy the right product for the job• Cost is part of the specification

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