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Speaker Specification Guide Part 2 – The Basics

This is the first real section of our Speaker Specification Guide. Covering the main components of a speaker, and the general basics of how the speakers work.

Within this guide when we refer to speakers we are generally referring to actual speakers as opposed to a cabinet of speakers, but the principles are the same.

Speaker Construction

Speaker Construction basicsThe main components of a speaker are,(see image to right)

  1. A strong metal frame,
  2. A diaphragm ( the bit that moves)
  3. A permanent magnet and closely wound coil of wire. (housed in enclosure)

The second image shows the face of a speaker with the diaphragm removed so the slot where the coil of wire fits can be seen, as per the arrow.

Speaker Components from Face diaphragm removedThe coil of wire is suspended inside the ring shaped magnet magnetic within its magnetic field and held in place by the movable diaphragm. It should not touch any of the metalwork around it (if it did the speaker would be considered to be off centre, and would not be usable)

How Does a speaker make a noise?

The Voltage that drives a speaker is an alternating current ( this means that it has no Direct Current (DC) element to it) An alternating current can be seen in the image below, it rises from 0 volts up to (in this example) +5 volts, then back down to 0 (zero) volts, and then down to -5 volts.It therefore is considered to have no DC content, which would destroy the speaker.

If this waveform is connected across a speaker coil an electromagnetic reaction takes place between the magnet and the coil, and the coil moves in one direction on the +5 volt positive half cycle, and in the reverse direction on the negative half cycle. As the coil is directly connected to the speaker diaphragm, the diaphragm moves as well, creating an audio tone by moving backwards and forwards in sync with the alternating current being provided to it. This Vibrates the air around it which carries the sound to our ears.

Alternating Current Speaker Drive wave Form Shown on Oscilloscope

Return To page 1 of  the speaker specification guide.

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