Typically, a loudspeaker will handle somewhere between 6 dB to 10 dB higher peaks than its long-term-average power rating, particularly in the case of the conservative EIA-426A standard used by several manufacturers.

This means that if a loudspeaker is rated for 100 watts long-term-average power, the amp driving it should be rated between 400 and 1000 watts – if the user does not compress the source signal. Once compression is used, all bets are off.

Generally speaking, the number one contributor to a transducer’s power rating is its ability to release thermal energy. This is affected by several design choices, but most notably voice coil size, magnet size, venting, and the adhesives used in voice coil construction.

Larger coil and magnet sizes provide more area for heat to dissipate, while venting allows thermal energy to escape and cooler air to enter the motor structure. Equally important is the ability of the voice coil to handle thermal energy.

Mechanical factors must also be considered when determining power handling. A transducer might be able to handle 1000 watts from a thermal perspective, but would fail long before that level was reached from a mechanical issue such as the coil hitting the back plate, the coil coming out of the gap, the cone buckling from too much outward movement, or the
spider bottoming on the top plate.

The most common cause of such a failure would be asking the speaker to produce more low frequencies than it could mechanically produce at the rated power. Be sure to consider the suggested usable frequency range and the Xmech parameter in conjunction with the power rating to avoid such failures.

Sensitivity: One of the most useful specifications published for any transducer, it’s a representation of the efficiency and volume you can expect from a device relative to the input power.

Manufacturers follow different rules when obtaining this information – there is not an exact standard accepted by the industry. As a result, it is often the case that loudspeaker users are unable to accurately compare the sensitivities of different products.

Eminence Speaker LLC and Live Sound/ProSoundWeb Senior Technical Editor John Murray contributed this article.

Also be sure to read Real World Gear: The Latest In Loudspeaker Drivers and take our Photo Gallery Tour of the latest driver models.

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