basics of sound systems and acoustics

1. Basics of Sound Systems and Acoustics Georgia Church Music Conference 2006

4. Microphone Types and Placement Omnidirectional Cardioid Supercardioid Hypercardioid

5. Omnidirectional Microphones These are the microphones that pick up more-or-less from every direction. Useful if you wish to pick up ambient sound. "Only have the mic on when you need it!!!"

6. Cardioid Family Cardioid microphones accept sound from one direction but reject sound from another. Their polar pattern in in the shape of a heart, rejecting sound from the back of the microphone.

7. The super cardioid mics have a similar same pattern, but have a more narrow shaped with a lobe at the rear of the microphone. A hyper cardioid has an even narrower shaped pickup pattern. This is useful when you want to capture sound from say a stage and not the audience. In a concert situation, you may want to catch the sound of the singer but not the sound from the monitor to help resist feedback.

8. Pattern Guide

9. Placement Pastor- Staff Ear, Belt Pack (lapel) Choir, Chorus (1:3 ratio) Microphone Stands, Overhead Instruments Brass, Winds, Strings, Acoustic Guitar, Electronic Instruments (Keys, Bass, Etc), Drums. Recording Natural Sound is best Direct

10. How Critical is Critical Distance Critical distance (Dc) is the point where the direct sound from the source equals the reflected sound from the room. Feedback Shallow, Hollow sound Poor intelligibility

11. Dynamic Vs Condenser Dynamic Microphones Actual energy to energy transfer 1:1 Accurate representation Low cost More durable than other types of mics Less sensitive (smaller sound field)

12. Condenser microphones Amplified transfer of energy 1: 2~? MUST HAVE PHANTOM POWER Extremely accurate Very sensitive (larger sound field) Less durable (humidity and shock) Some mixers have Global and some isolated. Check choir mics, podium mics, etcSome mixers have Global and some isolated. Check choir mics, podium mics, etc

13. Speaker Types Point Source --- (-6dB per doubling of distance, i.e.-inverse square law) Dispersion angles very important 2 way 3 way Subwoofer (is not God)

14. Line Arrays A Line Array in the truest sense is literally a straight line. --- (-3dB per doubling of distance) Line Arrays are cool, but not the best in many applicationsLine Arrays are cool, but not the best in many applications

15. Many variations of a Line Array exists. True Line J Line Curvilinear Array (JBL VRX900 and Similar)

16. Horizontal Arrays Very even horizontal coverage with expanded vertical coverage. Less expensive than Line Arrays. Reduced �comb filtering� Shorter throw distance

17. Cables and Connectors XLR (Microphone Cable) Three pins, Balanced connection. Pin 1 Shield or ground Pin 2 Hot or Positive Pin 3 Negative or neutral TRS (balanced ��, stereo instrument) Three pole, Balanced connection Tip, Ring, Sleeve Tip � Positive or Hot Ring � Negative or neutral Sleeve � Shield or ground

18. Unbalanced �� (basic instrument cable) Also known as a radio antenna Two connections Tip � Hot or Plus Sleeve � Negative and shield Balanced �� is by far better and more accepted.

19. Microphone Cable Small gauge 3 connector Speaker Cable *Speakon Connector* Heavy gauge 2 connector Signal loss is a factor. Instrument Cable Stereo Vs Mono TRS (Balanced) 1/4� (Unbalanced)

20. Signal Flow - Troubleshooting The most important thing about sound. What makes the noise, what effects the noise, what amplifies the noise, and what reproduces the noise and in what order

22. Troubleshooting Is the power turned on? Start at the very bottom of the �food chain� the transducers. microphones (signal source) Move forward taking into account all connections and cabling Try to isolate the one piece of equipment that is causing the problem

23. Mixing Channel Strip Trim/ Gain EQ Hi Pass Hi Hi- Mid Sweep Low-Mid Low Low Cut Aux Sends Separate Mix for Monitors and Recording Pre � Post Fade Pan Assignment Button Sub Groups (Blending) Mute Groups/ Mute Slider

24. Basics of Acoustics What is Sound?

25. Frequency - Hz Frequency is the number of pressure peaks that pass a given point in 1 second, Average hearing range is between 20Hz and 20,000 Hz. Middle C on piano is 256Hz

27. Control of Sound Consider wavelengths Acoustics are physical properties of air movement To control or effect sound, the wavelength must be smaller than the actual physical properties of the object or enclosure. Subwoofers Cars

28. Reverb vs. Echo Reverb is the decay of sound. (mostly indirect) Cathedral Echo is the direct reflection of a sound. Two parallel side concrete walls Not to be confused with Feedback.

29. Acoustic Treatment Absorption Reduces the total amount of reverb Diffusion Not necessarily used to reduce reverb but to cut echo. Diffsorbers Good Architectural Design is less expensive than acoustical treatment

30. Resources www.synaudcon.com (Syn-Aud-Con) www.shure.com www.crownaudio.com www.churchsoundcheck.com www.messengermediainc.com