A loudspeaker is a device that converts low-frequency electrical signals into sound. The task of the speaker is to enable the air in periodic oscillations – which in turn brings in the human ear drum to vibrate.
To convert the electrical signals into sound waves are displaced almost exclusively membranes into mechanical vibrations, which also gets the air to the membrane in motion. These membranes will normally act as a piston radiator, ie that the entire membrane is moved smoothly.
This is generally only – in relation to the membrane surface – to reach low frequencies. All membranes are divided into regions at higher frequencies which move in opposite directions, thereby arise naturally dead lines on which does not move the diaphragm. These phenomena are called partial vibrations.
There are different types of speakers such as the full-range speaker, Dome, Piezo speakers or horns. We will turn our attention here only to the full-range speaker, because it is often used.
Structure and Function
Speaker can be driven in various ways. Most common are the electrodynamic loudspeaker. It includes an annular permanent magnet in its center a freely movable coil, also called voice coil (spule). This voice coil is directly connected to the diaphragm.
Structure of an electrodynamic loudspeaker
If the alternating voltage applied to the voice coil, magnetic field generated in the voice coil. Depending on the direction of the magnetic field, the voice coil is repelled by the permanent magnet (the voice coil moves out of the permanent magnet) or attracted (the voice coil moves into the permanent magnets). Provided that the oscillation is transmitted in a frequency range of human ears, We perceive this as a tone or sound.
Speakers still have a polarity. Normally, this is such that the voice coil moves out of the permanent magnet. If the speaker is installed incorrectly, it swings to “wrong side”, that is backwards, which at high volume levels, can cause very strong vibrations, the diaphragm will strikes the rear, which can result in damage to your speakers. Therefore, we must pay attention to polarity when connecting speakers
Loudspeaker Impedance
Each speaker has a certain resistance, known as impedance. With a resistive impedance is meant, which is only available with an alternating voltage. Typical impedance values for today’s speakers are 4 or 8 ohms. Older speakers may also have a higher impedance.
