NAD The Power Envelope
We suggest the Power Envelope as a straightforward, easily understood, and musically appropriate way to assess the useful power output of amplifiers.
This method of presenting an amplifier's performance was first introduced by NAD at the January 1985 Consumer Electronics Show.
Since then it has been adopted by Carver, Proton, and by Julian Hirsch of Stereo Review in two amplifier reviews.
The Power Envelope, as a diagram or as a set of power ratings, is the clearest method of illustrating, and validly comparing, the musically useful power output of amplifiers.
It shows the rated maximum output that the amplifier can deliver, as a function of time.
It includes the two measurements, continuous power and IHF dynamic power, that are already standardized and familiar to consumers.
It extends the concept of dynamic power by measuring the amplifier's ability to deliver bursts of power lasting as long as a typical musical note, much longer than the 0.020 second On time of the IHF dynamic headroom test signal, and shorter than a constant full-power sine wave.
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