Maintenance of loudspeakers

Introduction

Loudspeakers are rugged devices and can take some amount of abuse. However they do have limits and exceeding them by a large factor almost always causes permanent damage.

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Tweeters

The tweeters are usually the first to go under circumstances of abuse, since they have the lightest voice coil made of thin wire which easily melts if the temperature rises excessively. Tweeters are usually designed (and rated) keeping in mind that a typical music signal doesn't contain a lot of power or energy at the higher end of the audio spectrum. Thus a tweeter rated for 50W is meant to be used with a 50W amplifier only if the signals below the tweeter's lower operating frequency are filtered out. Thus, feeding a low frequency (or a DC) signal to a tweeter even though electrically it may be within the tweeter's specification may cause permanent damage to the tweeter. A badly clipping amplifier may also damage the tweeter despite a crossover, since a clipped waveform generates high-frequency harmonics which can contain sufficient power to heat up the tweeter's voice coil.

Woofers

Most woofers (and mid-ranges) can easily take upto 1.5 times or more power than what they are rated for - however this is dependent on the particular driver and the duration of the abuse or overload. Woofers will usually take a lot of power before burning out or suffering damage to their moving systems. Physical damage occurs if the signal causes the woofer's cone displacement to exceed the safe Xmech limits for prolonged periods. In rare cases, a very loud signal may cause the coupling between the parts of the woofer to simply give way. A large DC fed to the woofer may cause twisting or deformation of the voice coil such that it rubs against the pole-pieces or magnet. Electrical damage occurs when the voice coil burns out. The latter two typically happen when the amplifier dumps a large DC current into the speaker - a condition typical of a failing (or failed) amplifier. In all cases, replacement or full repair of the driver are the only options.