Buying the right PA for your band 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 • Microphones Dynamic (moving coil) Condenser Pick-Up Pattern Style • DI Boxes (direct injection) Active/Passive Electro-Acoustics, Keyboard, Bass • Radio Mics, CD, DVD, PC
Cables, Connectors, Multicore • Balanced Cable
Cables, Connectors, Multicore • XLR pin 1 gnd, pin 2 +ve (hot), pin 3 -ve (cold) • JACK TRS: 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) EQ Routing: Auxiliaries Powered or Unpowered
Processors • Effects: Reverb, Chorus, Delay • Compressor/Limiters • Gates • Graphic Equalisers • Crossovers • Speaker Controllers
Amplifiers • Constant Voltage 100 v Line Speaker load not exceed 75% of amp power. • Low Impedance Example: 500 w into 4 ohm = 300 w into 8 ohm = 700 w into 2 ohm Allow for headroom up to twice speaker power
Speakers • Power: RMS = Continuous Program = 2 x Continuous Peak = 4 x Continuous • Sensitivity: SPL – Sound Pressure Level Ex: 400 w 96 d. B speaker is same level as 200 w 99 d. B speaker I. e. you need twice the power for 3 d. B increase in level • Add 2 nd speaker adds 3 d. B or 6 d. B if placed together
Speakers • Inverse Square Law: -6 d. B per distance doubled • • Dispersion Low Impedance/100 v 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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