Editing Audio power (section)

==Power handling==
In [[audio electronics]], there are several methods of measuring power output (for such things as amplifiers) and '''power handling''' capacity (for such things as loudspeakers).

=== Amplifiers ===
Amplifier output power is limited by voltage, current, and temperature:
* Voltage: The amp's [[power supply]] [[voltage]] limits the maximum amplitude of the waveform it can output.  This determines the peak momentary output power for a given load resistance.<ref name=":1">{{cite web|url=http://www.rocketroberts.com/techart/powerart_a.htm|title=Understanding Power Amplifier Power Ratings|website=www.rocketroberts.com|access-date=2016-10-28|quote=The peak of the signal is just touching [...] the values of the power supply rails. This signal is still clean and undistorted, however it is the maximum clean signal that is possible for this amplifier. [...] Peak Power: [...] the maximum amount of power that can be delivered to a load [...] For the amplifier we have been using in our example, the peak power (for an 8 ohm load) is 200 watts. This amount of power is delivered to the 8 ohm load at the instant when the output voltage of the amplifier is at +40 volts}}</ref><ref>{{cite web|url=http://www.meyersound.com/support/papers/amp_power.htm|title=Making Sense of Amplifier Power Ratings|website=www.meyersound.com|access-date=2016-10-28|quote=Using this rail voltage, we could calculate the instantaneous peak power...|archive-url=https://web.archive.org/web/20161019214511/http://www.meyersound.com/support/papers/amp_power.htm|archive-date=2016-10-19|url-status=dead}}</ref>
* Current: The amp's output devices ([[transistor]]s or [[Vacuum tube|tubes]]) have a current limit, above which they are damaged.  This determines the minimum [[load resistance]] that the amp can drive at its maximum voltage.<ref>{{cite web|url=http://www.sengpielaudio.com/calculator-AmplifierLoudspeakerAndOhm.htm|title=Amplifier, Loudspeaker, and Ohm|last=Sengpiel|first=Eberhard|website=www.sengpielaudio.com|access-date=2016-10-28|quote=If speaker impedance is too low [...] Too much current will run through the AV receiver's output transistors, causing the receiver to overheat and shut down.}}</ref>
* Temperature: The amp's output devices waste some of the electrical energy as heat, and if it is not removed quickly enough, they will rise in temperature to the point of damage.  This determines the continuous output power.<ref name=":0">{{Cite book|url=https://books.google.com/books?id=G-MDAAAAMBAJ&q=average+continuous+power+abbreviation&pg=PA101|title=Popular Mechanics|last=Magazines|first=Hearst|date=1987-12-01|publisher=Hearst Magazines|language=en|quote=The Federal Trade Commission has long been aware of this fact, and in 1975 stepped in to halt the abuses of companies that wanted you to think your amp could launch a speaker into orbit. [...] all published power specs have to state continuous power in watts [...] the average amount of power the amp is capable of producing over an extended period of time.}}</ref>
As an amplifier's power output strongly influences its price, there is an incentive for manufacturers to exaggerate output power specs to increase sales. Without regulations, imaginative approaches to advertising power ratings became so common that in 1975 the US [[Federal Trade Commission]] intervened in the market and required all amplifier manufacturers to use an engineering measurement (continuous average power) in addition to any other value they might cite.<ref name=":0" />

=== Loudspeakers ===
For loudspeakers, there is also a thermal and a mechanical aspect to maximum power handling.
* Thermal: Not all energy delivered to a loudspeaker is emitted as sound. In fact, most is converted to heat, and the temperature must not rise too high. High level signals over a prolonged period can cause thermal damage, which may be immediately obvious, or  reduce longevity or performance margin. 
* Mechanical: Loudspeaker components have mechanical limits which can be exceeded by even a very brief power peak; an example is the most common sort of loudspeaker driver, which cannot move in or out more than some [[Excursion (audio)|excursion]] limit without mechanical damage.
There are no similar loudspeaker power handling regulations in the US; the problem is much harder as many loudspeaker systems have very different power handling capacities at different frequencies (e.g., tweeters which handle high frequency signals are physically small and easily damaged, while woofers which handle low frequency signals are larger and more robust).