How to: Speaker specifications

Speaker specification pages can be at best a bit confusing—and at worst a complete mystery to the uninitiated. Here’s a quick guide to what the most mysterious terms mean:

Crossovers split the audio signal into separate frequency ranges which are reproduced by the drivers designed to work in those ranges. On the specifications sheet, the number, expressed in Hertz, represents the frequency at which these ranges meet.

Frequency response specifications will appear in this format: 21 Hz -29 kHz +/- 3 dB. The first number refers to the bass output, and the second represents the high end figure. The "+/-" after the frequency response number indicates that the performance will be within that tolerance.

LFE stands for low frequency effects. LFE output, often found on film soundtracks, requires a subwoofer for proper reproduction.

Nominal Impedance is a rating of a loudspeaker's affinity for absorbing power. Loudspeakers typically have ratings of 8, 6 or 4 ohms; the word “nominal” is added because the impedance generally changes with the different frequencies of music. The lower the rating, the easier it is to draw power from the amplifier.  In some cases it may be TOO easy, resulting in clipping and/or amplifier failure (letting the smoke out).

Peak power represents the maximum amount of power that the speaker can handle—momentarily—without incurring damage.

RMS as a measure of power is a misnomer.  Technically it is continuous power, which represents the average power when reproducing a single tone. NOTE: a higher peak or average power rating doesn’t necessarily mean that one speaker will be louder than another one; other factors, such as sensitivity, enter into the equation.

Sensitivity, many times incorrectly referred to as speaker efficiency, is the measure of the speaker's output in a specific direction (usually to the front) using a specified amount of power, usually one watt. The sensitivity figure is expressed in dB. Sensitivity below 85dB is considered (by Klipsch) to be very inefficient; speakers with a sensitivity surpassing 100dB are highly efficient.

Watt is a unit of energy, as is horsepower. In audio, an electrical watt is used to describe the energy output of a receiver or amplifier used to power a loudspeaker.