The following essay is from Sound Reinforcement 2 Outcome 1 and outlines Sound Reinforcement, system types, speaker types and RF types. It shows I understand how to construct and operate a sound reinforcement system and make necessary choices depending on the venue.
Outcome 3 SR2 Conor Devlin
Q1 – Purpose of Sound Reinforcement
The basic purpose of a sound reinforcement system is to take a signal (whether that be a simple spoken vocal, or a whole band setup) and amplifying it to a suitable listening level. Generally this will involve taking in the source signal, through either a microphone or a line input, running it through a mixer system, which will then send it to all the appropriate outputs (headphones, stage monitors, front of house speakers). This will often be overseen by an engineer (or team of them).
When dealing with sound reinforcement systems, you will often have to deal with some, if not all, of the following issues:
Tone – If there are issues with your system, the signal you’re trying to amplify will sometimes not come out the speakers sounding the same way it went in (intentional changes aside). This can be due to a number of factors, such as poor choice of microphone, microphone placement, issues with the mixer, issues with the speakers themselves or an issue with the cabling between any of these. This is a fundamental problem that cannot be fixed without revising your system and its parts in some way.
Dynamic Range – A system should be designed for purpose, if you have a system that is designed to broadcast announcements across a load factory floor and it doesn’t effectively allow the announcements to be heard, either due to not being loud enough or due to clashing frequencies, then you must revise the system to accommodate for these issues and allow the announcements to be heard.
Mono/Stereo Image – This is an issue that weighs heavily on the positioning of the listener. If you have a system with panned elements, such as a live gig with instruments panned left and right, then anyone who is significantly closer to one speaker than another will suffer a loss of those instruments. The most obvious way to deal with this is simply to play the audio in mono, that means that everyone will receive the same balance of instruments
Factors affecting sound quality – This is perhaps one of the most important issues that must be considered when designed a sound system. You must consider anything in the room that may be reflective/absorptive, because if you don’t you may find frequencies reflecting or being lost completely. You must also take into account that if you’re testing a a sound system for a gig in an empty venue, it’s going to sound different as to when you’re using the sound system to put on an actual gig and the room is full of people.
Q2 – System Types
Ground Stacked – This type is a vertical stack of speakers resting on the ground, to combat phase, they are placed sub at the bottom, with the tweeter on top. These systems are found in small to medium gig venues and at outdoor events; where they are used reinforce the people at the front of the stage.
Line Array – A Line Array is a vertical strip of speakers that is swung from the celling/top of the stage, and they contain many individually powered speakers. They are generally found at large venues, and more commonly at outdoor events, where they are used because they are very efficient reinforcing the middle to back areas of the crowds. They are usually angled to provide the maximum spread.
Analogue and Digital Multi-cores – The analogue multicore has three distinct parts; the box, the snake, and the tail. The box is where all the inputs are inserted, they are then carried down the snake to the tails where they are inserted into the desk to be mixed and sent. The digital multi-core works slightly different, the signals are converted from analogue to digital and are then carried down a single cable where they are received by a digital desk, which requires no further work. If you want to use a digital snake with a analogue desk, you must first run it through a converter, the disadvantage to doing this is that you will suffer some latency.
Analogue and Digital Mixers – A mixing desk is used to received, balance, equalise and send signals. An analogue mixing desk uses physical hardware to control the inputted signal, while a digital desk will do it all through its software. The difference between the two is honestly down to use, an analogue desk requires a lot of outboard equipment if you want to put effects on audio, while most digital desks have inbuilt effects units. Another advantage of a digital desk is that you’re able to save settings and recall them when required, such as fader positions and gain settings.
Q3 – Speaker Types
Externally Powered Speakers (PASSIVE) – These speakers do not have inbuilt power, and must be paired with a matched amplifier to operate effectively. They are generally lighter than their self powered counterparts, which makes them ideal for live events as moving them around will be significantly less hassle.
Internally Powered Speakers (ACTIVE) – Active speakers have an inbuilt matched power amp, reducing the need to make sure you have an appropriate power amp. The issue with this is that if theres an issue with the power it is much harder to fix than if you were using a passive speaker, as the issue is specific to the speaker and you’d have to open it up and fix it, instead of just replacing the amp.
Q4 – RF Systems
In-Ear Monitors – In-ear monitors (IEM) are small wireless fitted speakers than sit in the users ear used for foldback. This clears up the need to clutter your stage with monitors, or compromise between what two members would want coming out of their stage monitor.
Mics – RF microphones are handy for any situation that requires the user to be moving around a lot and come in two varieties, hand-held and hands-free. Hand-held function much like any other microphone, but instead output to a radio transmitter instead of a XLR cable. Hands free tend to be mounted on the head (on a headband or something similar) and give the user use of their hands. They too output to a radio transmitter.
Instruments – Instruments too can be integrated into RF systems, with many systems including devices that allow for Jack/XLR input.
Choice of Mixer – Soundcraft LX7ii
Choice of Amp – N/A
Choice of Speaker – Tannoy VQNET 60 / LD Systems MEI ONE IEM’s
Choice of Snake – Roland Digital Snake
The plan is to have one speaker either side of the stage, with their 60 deg conical dispersion they will adequately cover the room. However the issue with this is that there is a 20db drop off between the front and back of the room. I would however argue that this benefits the system, as we could set up a bar at the back of the room and the loss of db would allow the bar staff to hear orders better. The room is also small enough that even at 118db it is still adequate.
