What Exactly Is A Loudspeaker? |
Converting An Electrical Current Into Sound
A loudspeaker is an energy converter, basically converting electrical energy or currents into acoustic energy or sound. This conversion takes place in two stages; a) Current to Motion and b) Motion to Sound. The first stage involves passing the current through a wire which is in a magnetic field and then makes the wire move.
Using The Current To Create Motion
A coil of wire is then usually wound round and put inside a powerful magnet. The current is then passed through the coil to create motion, but as yet no sound. The sound level, or 'volume' depends on how much air the loudspeaker can move; for example a vibrating voice coil will be pretty quiet. To increase the sound level the coil is attached to a much larger surface called a diaphragm. The resultant vibrating diaphragm is then able to produce sound.
Our Loudspeaker!
The loudspeaker is now created, which can be used to reproduce sound either 'live' from a performing artist or from a recording. A loudspeaker produces sound by moving a diaphragm backwards and forwards. You normally can't see this with the naked eye but when then diaphragm is moved forward, air at the front is “pushed” while air at the back is “pulled”.
 However, if we do not isolate these two movements the air will effectively not move at all, resulting in little or no sound. The simplest way to isolate them is to put the speaker drive unit into a box or enclosure so that the “pushing” and the “pulling” are separated. The box is called a cabinet, usually because it's designed in such a way that high quality pieces of furniture are.
Without a cabinet, a loudspeaker would produce little or no sound!
Creating Bass, Mid-range And High Frequencies
Sound can be divided up into different groups or “bands” which are known as frequency ranges. We'd usually refer to these ranges as bass (reproduced by a woofer), mid-range (reproduced by a mid) and treble (reproduced by a tweeter).
A speaker, which is ideal for reproducing bass, will not be ideal for treble and vice-versa. It is difficult to produce a single loudspeaker unit, which perfectly covers the entire range of the human hearing so we generally divide the job between two or three loudspeaker units or more. A good example of a compact speaker is the Boston Acoustics Soundware 5.1 speakers, which holds a tweeter for the treble ranges and a mid for both bass and mid-range frequencies. Larger floorstanding speakers have more room to house more speakers.
Separating The Frequency Ranges
A small electrical circuit called a crossover divides the different frequency ranges. This passes different parts of an electrical signal to the different loudspeaker units. A two-way design has two separate frequency sections or divisions and a three-way design has three separate frequency sections and so on.
Crossovers can either be active or passive. Active crossovers are usually built into amplifiers; passive crossovers are built into loudspeaker systems allowing the customer their choice of amplifier.
Further Technology
It simply doesn't stop there either. Different loudspeaker manufacturers use different techniques to disperse that sound in wider areas. Experiments with materials to engineer a high performance tweeter is common.
 
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