Sound Systems

1. Sound Systems The Basics and More

2. Basics and More • The Cost of Safety • How Sound Travels • Cables • Microphones • Speakers • Electronic Equipment • How this relates to musicians • How this relates to GOD • Question and Answer

3. The Cost of Safety • Electrical • Cables • Volume Levels • Dollars and Sense • Rigging

4. Electrical Safety • When handling high voltage connectors, grasp them with the outside of the hand NOT the inside • Do NOT unplug a connection by pulling on the cord • Do NOT lift earth ground connections

5. When you are electrocuted on the hand one of two things could happen. Your hand will close up if shocked on the inside and will open and pull away when shocked on the outside Pulling connections by the cord could cause electrical shock or damage to the cord or the equipment it is attached to Lifting the earth ground removes protection for you and the equipment designed to use it Electrical Safety

6. Cable Safety • Putting tension on a cord and using tangled cords creates hazards • Stepping on cords damages them and could damage the equipment they are connected to

7. Look down when walking on a stage and avoid running. Keep the cords out of walking areas Use extra caution when a stage is dark as most cords will become almost invisible Do NOT step on or place things on cables. They can be damaged by such things as hard soled shoes, stands, chairs or other objects Cable Safety

8. Volume Level Safety • The threshold of pain is 120 decibels and can cause temporary hearing loss • Permanent hearing loss beings at 140 decibels

9. Avoid long term exposure to high volume levels that lead to permanent hearing loss. Examples are a live concert or playing headphones loud enough that your ears wax within a couple of minutes Hearing damage caused by high volume levels is permanent in most cases. If you feel you need to cover your ears or you are beginning to feel pressure then this should tell you the volume is too high Volume Level Safety

10. Dollars and Sense • High quality does NOT always relate to high durability • Properly maintaining the components of a sound system can extend their life

11. Some of the most expensive equipment is also the most delicate No one product is indestructible High quality can come with a high cost of upkeep. Ignoring that cost can increase the risk of failure and cost and damage to other equipment Dollars and Sense

12. Rigging • California seismic code requires that ALL overhead rigged lights or other equipment MUST have safety cables • ALL stage props for productions or otherwise MUST be fire retardant • Improper rigging is an insurance claim waiting to happen

13. How Sound Travels • Frequency verses directionality • Frequency verses perceived volume level

14. How Sound Travels • Frequency verses directionality • The lower the frequency the less directional it is • The higher the frequency the more directional it is

15. How Sound Travels • Frequency verses perceived volume level • The lower the frequency the longer it takes to fully develop • The higher the frequency the less time it takes to fully develop

16. Cables • How they work • Care and handling • Different types of cables

17. Cables • How they work • They consist of strands or solid wire made of either copper, tin, silver or gold. Then these wires are insulated with a rubber or plastic compound • Cables can have many of these insulated wires together to meet various design needs • Shielded cables are the same but have stranded wire or foil that completely covers the inner wire. This outer wire is commonly called the ground or shield

18. Cables • Care and handling • Kinks in cables are one of the most common causes of failure • Connectors are the second most common cause of failure • Improper wrapping of cable causes tangles and leads to cable damage • Excessive tension or pressure where the connector and cable come together is another common cause of cable failure

19. Cables • Different types of cables • Microphone cables are used primarily for connecting microphones to a sound system. These commonly use XLR connectors. • Speaker cables are used to connect speakers to a sound system. These use speakon, 1/4 inch, banana plug or bare wire connectors depending on the installation

20. Cables • Different types of cables (continued) • Patch cables are used to connect sound equipment together or are used in a patch bay. These use 1/4”, RCA ,XLR or TRS connectors depending on the equipment or patch bay design • AC cables or extension cords are used to connect sound equipment to electrical outlets. These should be kept away from the other types of cables for noise reasons and shouldn’t run parallel with audio cables

21. Microphones • How they work • Care and handling • Connecting • Positioning

22. Microphones • How they work • They are technically called a transducer. This is because they convert one form of energy to another. They convert sound waves in the air into electrical sound waves that run through wire • They consist of a diaphragm that moves with the sound waves in the air. This is converted by inductance or capacitance and then into an electrical representation of the sound wave

23. Microphones • Care and handling • They should be stored in a dry, well padded case • They should not be held by the cable unless by design • They should not be hit or dropped • They should not be used near water

24. Microphones • Connecting • Turn off or mute the channel you intend to connect the microphone to. Then connect it • Do not just pull a connector out of a microphone without first wiggling the connector. This is done to ensure the internal microphone connection is not pulled out along with the cord connector if it were loose.

25. Microphones • Positioning • Do NOT aim a microphone directly at a monitor or speaker • Make certain the microphone follows your mouth • Angle the microphone at roughly 45 degrees from your mouth • Keep the microphone within two to six inches from your mouth • Do NOT use omnidirectional mics around monitors

26. Microphones • Positioning (continued) • Choir or overhead mics should be aimed at the top row of singers and placed a few feet from the first row of singers. Large choirs or groups require more mics using similar techniques. • Boundary mics should be placed one or more feet in front of the speaker on a hard surface at waist or chest level or on a floor depending on the application.

27. Microphones • Positioning (continued) • Lapel mics should be 2 to 3 buttons down on a collared shirt. If the mic is omnidirectional then dropping down to the 3d or 4th button is preferred • Headset mics should be worn so that the mic is aimed directly at the mouth or cheak depending on the design

28. Speakers • How they work • Care and handling • Connecting • Positioning

29. Speakers • How they work • They are also a transducer for the same reasons a microphone is • They convert an electrical representation of a sound wave into sound waves that move air that the human ear can perceive • They consist of single to multiple cones, domes or diaphragms that move air to create sound waves by either electrical inductance or capacitance

30. Speakers • Care and handling • They should be stored in a dry place • They should not be driven to the point where there is audible distortion • They should not be under or dramatically over powered as these are the most common causes of speaker damage

31. Speakers • Connecting • They should be connected with the proper gauge of wire for the power they will need to operate optimally • Do NOT disconnect speakers while they are playing unless the amplifier used can tolerate this • Do NOT connect more than two speakers in parallel to one amplifier unless it is rated to support it

32. Speakers • Connecting (continued) • Most average to high quality speakers used for sound systems are rated for at least 200 watts. It is not uncommon to see 600 or 1200 watt ratings. Even if you can connect or disconnect a speaker when powered to full output. A word of warning. I know of a technician that used a high quality 300 watt amplifier for light arch welding

33. Speakers • Positioning • The main speakers should be mounted between the stage and audience and directed at the audience • Most speakers are designed to work optimally in the upright position with few exceptions • Whenever possible ALL microphones should be behind the main speakers • When positioning monitors consider the polar pattern of the mic you are using

34. Speakers • Positioning (continued) • Monitors should be pointed up at the performers • Avoid excessive monitors to control feedback and stage volume • Do NOT place monitors side by side or within roughly six feet of each other • Subwoofers should NOT be in close proximity to mics • Subwoofers should NOT be given microphone signals

35. Electronics • How they work • Care and maintenance • Powering a sound system • Using a Cassette Deck • Using a CD Player • Using a Direct Box • Using a Mixer

36. Electronics • How they work • Most analog electronic equipment in a sound system consists of multiple amplifiers. These slowly increase the levels from a small signal that would come from a guitar or microphone to a level sufficient to power a speaker

37. Electronics • Care and maintenance • Equipment should be kept in a dry place away from water and dust • Equipment should be kept away from high power wires and motors that are commonly found in refrigerators, air conditioners and other similar devices to minimize noise and other forms of electrical interference • All equipment should be grounded properly to prevent fire and electrical shock hazards

38. Powering a sound system on in order Cassette decks, CD players, equalizers and other similar equipment The Mixer The Amplifiers Powering a sound system off in order The Amplifiers The Mixer Cassette decks, CD players, equalizers and other similar equipment Electronics

39. Electronics • Powering a sound system (continued) • Devices with moving parts like CD players or Cassette decks could react poorly to high humidity or cold weather. In these cases leave the equipment on roughly half an hour before using

40. Electronics • Using a Cassette Deck • If the tape is not wound tightly on the reels then use a pencil or other device to remove the slack. Some lower quality decks will eat a tape for this reason alone • If the deck does not have auto bias selection make sure to pick the right setting • Do not use metal tapes on decks that are not designed for them. This will wear out the tape head pre-maturely

41. Electronics • Using a Cassette Deck (continued) • To cue a tape rewind the tape to the point where the track will start. Play the tape and listen for the song to begin. As soon as the music starts press Stop on the deck. Remove the tape and use a pencil or other device to turn back the reel approximately one and a half turns

42. Electronics • Using a CD Player • When cleaning CD’s use a soft dry cloth and move from the inside to the outside • Keep CD’s away from direct sunlight, high humidity or excessive heat • Do NOT write on the top of a CD unless you know the pen you are using has no alcohol in the ink • Do Not place labels off center on the CD as some players will not play the disc due to wobble

43. Electronics • Using a CD player (continued) • Cueing a CD is as easy as inserting the disc and selecting the track and pressing play. Older players take longer to start up so selecting the track and then pausing the player may help make up for this delay

44. Electronics • Using a Direct Box • A Direct Box is also known as an Impedance matching transformer • This device should be used when connecting unbalanced, high impedance devices to a sound system, such as VCR’s, TV’s, computers, electric guitars, keyboards and other similar devices • Active versions require a battery or can run from phantom power • Lifting the ground should be used only as a temporary solution

45. Electronics • Using a Direct Box (continued) • This device may not be needed if the cable run is under 25 feet and there is a high impedance input on the sound system • These devices come in passive and active versions. The active version is more versatile and is better at isolating noise • They are connected to the sound system with a microphone cable and connected to a microphone input in most cases

46. Electronics • How to use a Mixer • This is the most versatile and thus can easily be considered the most confusing part of the sound system • Try not to look at the whole board but look at the area you need too and focus in from their. Much like reading a map you first get the cross streets and then the address

47. Electronics • How to use a Mixer (continued) • The controls in each channel: • Trim: This is the first volume control for the channel. It has a very broad range of level to cover most every option • Line/Mic: This is a switch to select between the line or mic input. This way you can have multiple devices on one channel and pick which one you want to use

48. Electronics • How to use a Mixer (continued) • Phantom Power: This is a switch to provide 49 volts of power for mics or direct boxes that require it • High Frequency Control: This is much like the treble tone control on your home stereo. It adjusts the amount of gain or cut in the high frequencies • Mid Frequency Selection: This control allows you to pick the frequency you will boost or cut in the mid frequency range

49. Electronics • How to use a Mixer (continued) • Mid Frequency Control: This is much like the Midrange tone control on your home stereo. It adjusts the amount of gain or cut in the midrange frequencies • Low Frequency Control: This is much like the Bass tone control on your home stereo. It adjusts the amount of gain or cut in the bass or low frequencies • Aux Sends: These allow you to direct signal from one channel to one of the Auxiliary buses

50. Electronics • How to use a Mixer (continued) • Sub Group assignments: This allows more control over where the signal from the channel will go • Pan Control: This is much like the balance control on your home stereo. You can select where the signal will go • Mute: This does exactly what it sounds like. It mutes the signal coming out of the channel