Editing Audio power (section)

==Matching amplifier to loudspeaker==
Charles "Chuck" McGregor, while serving as senior technologist for [[Eastern Acoustic Works]], wrote a guideline for [[professional audio]] purchasers wishing to select properly sized amplifiers for their loudspeakers. Chuck McGregor recommended a rule of thumb in which the amplifier's maximum power output rating was twice the loudspeaker's continuous (so-called "RMS") rating, give or take 20%. In his example, a loudspeaker with a continuous power rating of 250&nbsp;watts would be well-matched by an amplifier with a maximum power output within the range of 400 to 625&nbsp;watts.<ref>[http://www.prosoundweb.com/article/how_many_watts_loudspeaker/ ProSoundWeb, Study Hall. Chuck McGregor, ''How Many Watts : Amps vs. Loudspeakers: The eternal question answered - what's the "right" wattage for my loudspeakers.''] Retrieved February 27, 2009.</ref>

[[JBL]], which tests and labels their loudspeakers according to the [[IEC]] 268-5 standard (called IEC 60268-5 more recently) has a more nuanced set of recommendations, depending on the usage profile of the system, which more fundamentally involves the (worst case) [[crest factor]] of the signal used to drive the loudspeakers:<ref name="jbl">[http://www.jblpro.com/pub/technote/spkpwfaq.pdf JBL Speaker Power Requirements]</ref>
# For "carefully monitored applications where peak transient capability must be maintained, a system should be powered with an amplifier capable of delivering twice its IEC rating." As an example, a [[studio monitor]] rated at 300 watts IEC, can be safely driven by a 600-watt (RMS) amplifier, provided that "peak signals are normally of such short duration that they hardly stress the system's components".<ref name="jbl"/>
# For "routine application where high continuous, but non-distorted, output is likely to be encountered, a system should be powered with an amplifier capable of delivering the IEC rating of the system". This includes most consumer systems. "Such systems can often be inadvertently overdriven, or can go into feedback. When powered with an amplifier equal to their IEC rating, the user is guaranteed of safe operation."<ref name="jbl"/>
#  "For musical instrument application, where distorted (overdriven) output may be a musical requirement, the system should be powered with an amplifier capable of delivering only one-half of the IEC rating for the system." This necessary because, for example, an amplifier normally outputting "300 watts of undistorted sinewave" can reach closer to 600 watts of power when [[Clipping (signal processing)|clipping]] (i.e. when its output is closer to a [[Square wave (waveform)|square wave]]). If such a scenario is plausible, then for safe operation of the loudspeaker, the amplifier's (RMS) rating must no more than half the IEC power of the loudspeaker.<ref name="jbl"/>