Tim Price FdSc 2A
15th January 2010
D4: LIVE SOUND ENGINEERING.. THEORY
The role of an audio engineer is no longer exclusive to the recording studio. The skill set of a modern engineer extends to video, radio, graphics and many more. One of the key growth areas for ﬁnding employment opportunities in the sector, is that of live sound engineering. The theory of live sound is one which combines the two things present in most musical engineering, technical ability and intuition. Each one is as important as the other, a live sound engineer has to be able to be a master of both their equipment/set up, and of the live sound mix which can differ vastly from an in studio mix, applying different techniques and principles. At the core of the live sound set up are 2 things, the mixing desk and the speaker system/rig. The applications of the mixing desk in a live situation show many differences compared to its use in a studio, even in the earliest stages such as choosing the type of desk! For instance, in most instances a live engineer would lean towards using a digital mixing desk as apposed to the generally more desired analogue desk in the studio situation. One of the prime reasons for this is that a digital desk can contain audio processing equipment within its interface, such as gating and compression. These are available at the touch of a button, as apposed to the outboard equipment used in a studio. This feature can help save valuable time when mixing a live event, this example shows one of many advantages of using a digital desk for live. ‘Live in Cotgrave...’ An image capturing the digital yamaha desk, courtesy of Merlin PA’s live sound engineers.
As well as there being 2 types of mixing desks, in the live sound sector there are 2 main uses for a desk. The most obvious is for bringing all the signals to the main speakers and creating the mix, this is known as front of house (FOH). The other is for stage monitoring, creating a mix or separate mixes for the musicians particular taste(s). At bigger events, often there are 2 desks in play, one for the front of house and one speciﬁcally for the on stage monitoring.
EM LIVE LOUNGE
Front of house mixers usually come with a set number of input channels; 12, 16, 24, 32, 40 and 48 channels are what is usually found, specialized mixers used for bigger rigs can be sizably larger. The use of this large number of channels can range from the close micing of a drum kit and guitar amps, to the music used between acts and pre recorded tracks used in a set. Another use for having so many channels is if a show with many acts on the bill is taking place, and bands settings need to be set. However, with the advancement of digital desks with recall systems and ﬂying fades, needing to manually save a live mix has almost become a thing of the past. The features on a mixing console vary with the expense of the desk, but the regular features include:
- Input sockets (typically XLRs for mic and DI signals) - Phantom power, phase inversion (important for sorting out phase issues in a live mix, especially is the mix contains identical signals, e.g. the mix and line signals from a bass guitar) - Pad (reduces the signal by a set amount, typically -10db, this is useful for controlling over loud signals, such as a over eager guitarists amp) - Gain control (to set each signal at a sensible level before mixing) - Equalisation (this comes on all desks, both live and studio based, however in live the tendency is to use an external graphic Eq in order to meticulously notch out those problem frequencies) - High and Low pass ﬁlters - Panning - Auxiliary send (used for effects and vastly used later for the monitor desks One feature of most, if not all desks, that is utilised greatly in live sound are the sub group faders. This means that once a sub mix (e.g. the drum kit) is mixed, the faders can be assigned to a sub group with a singular fader to...
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