Live Sound

Live Sound

Monday Lesson 2 - 3/9/12

Mixers, Mics and Foldback Monitors

The lesson was held in the theatre where we were shown a few things about microphones, mixers, monitors and health and safety. 

We started by collecting some equipment from the area above the main theatre. We got 2 foldback speakers and a mixer. 

We ran a cable from a power supply through some surge protected power bricks. It's important to use surge protected power supplys to protect the equipment and also because if there was a fire it wouldn't be covered by insurance.You would usually duct tape the cables down for health and safety to prevent people tripping over the cables.

We use IEC power cables (also know as a kettle lead) to provide power to the mixer and fx unit. 

We discussed two different microphones the shure SM58 and the SM58 Beta A. 

The Sm58 is the current industry standard. It is a dynamic mic designed to take a beating and is often seen at venues, on tv and is one of the most commonly used mics. It's priced around 60 pounds it captures low and mid ranges and can be used for vocals. 

The Sm58 Beta A is also a dynamic mic with a few differences. It captures some high end and has a feedback response unit which provides less feedback while monitoring. It's priced at 120 pounds and is starting to become the standard. The price being double that of an sm58 is one of the reasons the sm58 is the industry standard at the moment. The Sm58 beta A is great for capturing vocals where a good performance on an Sm58 would sound great on the Sm58 beta A.

We connected the mixer to an IEC cable to the power supply and also connected the active foldback speaker to a power supply as well. Making sure the volumes are down on the mixer, we connected a (mono?) jack cable from the active speakers output to the passive speakers input and connected a (stereo?) from the jack output on the mixing desk to the jack input on the active speakers balanced line input. 

A mono cable is indentified by a single black ring around the plug and a stereo cable is identified by two black rings. 

The monitors are magnetically shielded to prevent damage to computer monitors. If it was not shielded this could destroy a computer screen. 

We then turn the gain on the first channel (which is where the microphone is plugged in) to 12 o'clock maybe a little bit more, increase the fader on channel 1 to send the signal to the master output and push the fader on the master up. We also turn up the volume on the monitors so we can hear whats coming through. Hearing the sound isn't massively important at this stage as we will see the led volume meters moving if there is a sound coming through. 

We check the level of the microphone (either 1-2, 1-2-3 or by telling a joke!). We adjust the volume to make sure the at the loudest use the meter won't go into the red as this would cause distortion. 

Mixers have different amounts of channels, the one we was using had 8 mono channels and 2 stereo channels.

Now that we had connected up a microphone we talked a little about eq. Eq stands for equalisation. Eq is used for several things one is adjusting the sound coming through the microphone. If the vocal was coming through very boomy we could turn down the low and get a less boomie sound (or increase for a big boomie sound!) and we can adjust the high end to get a brighter clearer sound by turning it up a bit it can make vocals sound nicer and clearer. 

We then looked at adding an effects unit into the mixer. We turn down the faders so that we don't have any loud bangs or pops while connecting audio equipment We then removed the connection from the speakers and put a jack from the mixers channel out into the effects unit in, and connected a jack cable from the effects unit output to the mixers auxilary return. 

We removed the microphone from the xlr input and connected a mono cable from a guitar into the first mono channel on the mixer. As the guitar is a line level instrument the signal will be very weak we could mic up an amp and connect this to the xlr input,. but these days it's much more convienient to use a DI box between the guitar and channel input to boost the signal. 

We didn't use a di box for this instance and the signal came through very quiet. We was going to look at some effects on the fx unit but there was a problem and we was unable to do much more.

Health And Safety

Health and safety is massively important in the music industry. Working with artists, venues and the general public it's important to have a grasp on the various risks involved in live and recording environments.

Cables - All cables should be duct to the floor to prevent anyone tripping up.

Surge protectors - protect equipment and can prevent fires. Microphones/speakers can be blown if theres a surge.

Heavy equipment - can be dropped on feet or people damaging both equipment and the person involved. 

Pop/loud noises/feedback - can damage equipment and ears. 

Liquids/Food - Can damage equipment such as mixers and cause fires. 

Overcrowding - Can cause problems such as crushing or if theres a fire risk to getting out safely. 

Mic stands - Can fall over damaging equipment or hitting someone.

Mixing desk/movable equipment - If breaks aren't set on movable equipment this can be a hazard to both the equipment and people. 

Safety breakers - Knowing where the breakers are at a venue can be vitally important if theres a fire or electrical accident.

Cables - If their not correctly coiled or duct to the floor can be tripped over.

Running - Can be dangerous you could fall over and hurt yourself, or fall into equipment and damage the equipment.

Checking a monitor with ear next to it - can be very dangerous can seriously damage hearing if someone turns volume up or shouts into a microphone.