Lexicon Performance

The power is a physical quantity that indicates how much Energy is converted or transmitted per unit time. The unit of measurement is the Watt.

The electrical power at a load is the product of a current flowing through a load with the voltage dropped across the load. In most cases, the energy thus delivered to the load is ultimately largely converted to heat. In the case of an electric heater, this is the sole purpose, and the power rating of the heater in watts gives the amount of heat produced per unit time.

Other electrical devices convert only a portion of the power received into heat, and the rest is given off in some other way. An electric motor, for example, releases some of the absorbed electrical power as mechanical power. A radio transmitter emits some of the absorbed electrical power in the form of electromagnetic waves. In such cases, the heat emitted is usually an undesirable by-product to which a loss of energy corresponds. This heat generation is therefore referred to as power dissipation. The ratio between the power emitted in the desired form and the power drawn from the mains is called the efficiency of the device, which is often expressed as a percentage.

In the hi-fi sector, power is of particular interest in the case of loudspeakers and power amplifiers. Here, the amplifier should deliver the energy, which the speaker then converts into sound.

The actual power delivered by an amplifier depends on the type of sound signals played and their desired volume. Normally, this is far below the power specifications of the amplifier or speaker. For room volume, most loudspeakers require a power of far less than one watt. The power specifications of loudspeakers and amplifiers therefore refer rather to theoretical limit cases, which are determined with the help of measuring signals.