Chapter One: Basic hardware elements of a mobile DJ:
So - you were thinking of starting up as a mobile DJ? Great! - it can be a good way to earn money whilst indulging in your passion for music and entertaining people. In this, the first article in the series, we'll take a look at some of the basic building blocks you'll need to be able to start up as your own one-person show.
There are three main elements to your mobile DJ setup. These three "blocks" are roughly as follows:
- Music/sound source or input.
- Music/sound amplification and processing.
- Music/sound output.
Let's have a very brief look at each of these components in turn -
All music is sound, but not all sound is music! As this may be a bit confusing, we will refer to the sound that the human ear can detect as "audio" (as in "audible"). This means that no matter what sound we present to our audience, it will all be called "audio" for the sake of simplicity.
Generally, as a mobile DJ, we want to fulfil our clients need for dance or background music for their various events, such as weddings, birthday parties, corporate events and other important occasions. Our music is obtained either from CD's, vinyl records or digital downloads from the Internet. We will discuss the various types of audio recordings in a later chapter.
These days, the vast majority of music is stored in digital format and stored on disk within a computer. Again, being a mobile DJ, the majority of those computers will be of the "laptop" variety. These laptops will now be your primary audio source, or input. Secondary sources may be microphones for speech, among others. We'll get to those later.
Audio processing and amplification
The audio output from your laptop will be far too low to be heard by a room full of people. In addition, the audio may sound a bit too bright (treble notes), or it may have too much low-frequency audio (bass notes). This is where we will use audio processing and amplification.
In general, we will pass the audio through some kind of filtering to alter (if necessary) the sound to be more pleasant to the ear, and to make it very much louder, so that the audio can be heard by many people - sometimes hundreds of people.
The filtering or altering of the audio signal is called equalisation, often abbreviated to "EQ". When we refer to "the EQ", we refer to the filtering and/or altering of the audio signal to sound better to our audience. If it sounds OK as it is, we may not have to apply any EQ at all. We will investigate equalisation or EQ in later chapters.
However, we will have to make our audio signal very much stronger to be heard by an audience, and for this, we will need to amplify the signal. This is done by passing the audio signal to a power amplifier.
Power amplifiers come in two forms: the stand-alone power amplifier and power amplifiers built into speakers, which is very common nowadays. A power amplifier takes a low-level audio signal from our audio source and makes that signal very much bigger - in fact, thousands of times bigger. This is necessary to power our third basic component - our output, which, as you no doubt are familiar with - the speakers.
In order to convert electrical signals from the power amplifiers into audible music or speech, a way of producing fluctuations in air pressure is necessary. After all, sound is nothing more than varying patterns of air pressure on our eardrums.
The conversion to audio is performed by the speakers. Speakers come in many shapes and forms, but the most common type of speaker for DJ-ing is in the shape of a box, known as a cabinet, and containing one or more drivers (which is the name for the actual mechanical device inside the speaker cabinet). So A speaker will consist of the cabinet and its associated driver(s).
Speakers receive a high-level signal from the power amplifier and use that powerful varying electrical signal to drive a coil of wire back and forth within a magnetic field. The coil is attached to a cone (usually of paper) that will then vibrate back and forth to produce differences in air pressure, which is the sound our audience will hear.
Most speakers will have some way of splitting the higher audio signals from the lower ones as it is very difficult to produce a speaker that can efficiently handle all the audio frequencies that the human ear can handle, and that method will employ multiple drivers within the same cabinet.
In its most basic form, the equipment a DJ will need to produce a good level of audio reproduction to an audience is:
- A good audio source - whether live input (microphone), analogue (turntables) or digital (CD's, MP3's etc)
- Some way of amplifying the low level of audio output from the source, and
- A speaker system capable of transforming the output of the amplifier into clear audio for the enjoyment of your audience.
In Chapter Two, we will look at the differing audio sources in more detail, including microphone signals, turntable signals and the different types of digital music formats available, such as WAV files and MP3 files.