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How speakers WORK?

A speaker is comprised of a cone made of paper, Kelvar, or similar material that is suspended from a rigid frame in a way that will allow it to move in and out of the frame. At the center of the cone, a coil of magnet wire is attached to it and connected to the  amplifier. This is the voice coil. A stationary permanent magnet is mounted in very close proximity to the voiceSection of a Speaker coil in such a way that a current flowing in the voice coil will cause the speaker cone to be attracted to or repelled from the permanent magnet. The cone will act like an air pump of sorts. It will move in and out at the same frequency as the signal applied to the voice coil, and with an intensity that is determined by the amount of power in the voice coil and the strength of the magnet.

Speakers are rated in Ohms (the impedance of the voice coil), Watts (the power handling capabilities of the coil), Frequency response (The range of audio frequencies where the coil is most efficient) and SPL or Sound Pressure Level (a relative measure of overall efficiency). SPL ratings are an indication of how much electrical energy a speaker can transform into air movement. The higher the number, the more efficient the speaker.