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A. The output of a speaker (measured in decibels (dB)) for a given amount of amplifier power is termed its efficiency. Speakers with high efficiency will require less amplifier power to produce a given sound pressure level. Live music and movie soundtracks have peak levels as high as 120 dB. To attain just a 3 dB increase in volume, an amplifier's power must be doubled regardless what the speaker efficiency. Therefore, the amount of amplifier power needed if you wish to attain the sound pressure levels of a live orchestra or a large explosion in a movie is greatly dependent on the efficiency of your speakers. Here is a chart that shows two different speakers, one with 88 dB efficiency (common) and one with 100 dB efficiency, and the amplifier power need to produce given sound pressure levels:
The above charts show that the typical speaker with a sensitivity of 88 dB requires 1024 watts just to get to 118 dB! A more efficient speaker (example here is our KLF-30) requires just 64 watts to hit those levels of live music and Home Theatre. Therefore, the amount of amplifier power that a person needs is determined by the efficiency of the speaker that person is using plus the desired dB levels he or she wants to be able to produce. Other variables which impact the choice of amp power are the size of the listening room, the absorption characteristics of the wall and floor surface materials and the distance between listener and speakers. In a smaller room and with high efficiency speakers, 50 watts may be enough to provide full dynamic range. In a large room with low efficiency speakers, even 500 watts may not be enough. Higher speaker efficiency always helps deliver the most from whatever power you choose.
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