Speakers come in all shapes and sizes, enabling you to listen to music on your mobile, tablet, laptop and home audio system, enjoy a film at the cinema or hear a friend’s voice over the phone.
In order to translate an electrical signal into an audible sound, speakers contain an permanent magnet and an electromagnet, Electromagnet is a metal coil which creates a magnetic field when an electric current flows through it. This coil behaves much like a normal (permanent) magnet, with one particularly handy property that is reversing the direction of the current. This causes flips in the the poles of the magnet.
Inside a speaker, an electromagnet is placed in front of a permanent magnet. The permanent magnet is fixed firmly into position whereas the electromagnet is mobile. As pulses of electricity pass through the coil of the electromagnet, the direction of its magnetic field is rapidly changed. This means that it is in turn attracted to and repelled from the permanent magnet, vibrating back and forth.
The electromagnet is attached to a cone made of a flexible material such as paper or plastic which amplifies these vibrations, pumping sound waves into the surrounding air and towards your ears.
Inside a speaker:
2. Electromagnet (coil)
3. Permanent magnet
The frequency of the vibrations governs the pitch of the sound produced, and their amplitude affects the volume – turn your stereo up high enough and you might even be able to see the diaphragm covering the cone move.
To reproduce all the different frequencies of sound in a piece of music faithfully, top quality speakers typically use different sized cones dedicated to high, medium and low frequencies.
A microphone uses the same mechanism as a speaker in reverse to convert sound into an electrical signal. In fact, you can even use a pair of headphones as a microphone!
Being an electromagnet, usually, speaker don’t do much different if connected in opposite direction in circuit. But mostly, for better quality and stable operation, we connect the speaker in proper polarity, that is the negative terminal of speaker must go to circuit ground.
The audio frequencies are broadly categorized in three types
1. Low Frequency (our bass Sound)
2. Mid Frequency ( Sounds, and vocal sound)
3. High Frequency (treble and sharp Sound)
Although any general purpose speaker can reproduce all these three frequencies equally, still if we are much concerned about quality, there are different types of speakers used for reproducing different frequencies nicely. These are listed below
A tweeter is a small speaker which is capable of reproducing high frequencies very nicely. It’s very small in size and can reproduce all the high frequency sounds very nicely which includes all the metal effects and very sharp sounds
Woofer is relatively large in size and its used to properly reproduce the low frequency sound. The Special Dhoom Dhoom we hear in audio is reproduced by woofers. These are large, requiring large space and large power as well
In this term, speaker is the one which can reproduce the mid frequencies well including vocal sounds sung by singer etc.
The one shown in above diagram is the general purpose speaker that we use in electronic experiments. Usually every speaker is assigned with some value like 16 Ohm speaker, 8 Ohm speaker. This configuration is for advanced user who wish to make the maximum output of it by tuning its amplifier. For us, for simple experiments, any small speaker does the job with more or less Loudness