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Speaker efficiency vs. power requirements

Recently someone gave me the "math" behind speaker efficiency ratings and power requirements. Although I am not sure if the information below is 100% accurate, it is what I have been told. Can we lay this on the table for discussion and try to resolve this confusing issue once and for all?

0 db is a power ratio of 1. Records and tape have dynamic ranges of 30-40db. To achieve a 30db dynamic range requires a power ratio of 1,000:1 and 40 db requires 10,000:1. So if you assign 1 watt of power to a speaker yielding 90db SPL, you need 1000 watts to deliver a true 30db dynamic range. With digital material we find dynamic ranges of 60-70db requiring power ratios of 1,000,000:1 & 10,000,000:1 respectively. Power amps of 1-10 million watts are not feasible today but the point is, more power offers more dynamic realism. Forget power vs. loudness because that really is not a factor in the overall scheme.
bwhite

Showing 1 response by rockvirgo

rockvirgo
587 posts
 
Power ratio??? Never heard of it. What is it?
It appears the flaw in your reasoning is that speakers rated at 90dB can and often do play at much lower levels. By definition a person can hear any level of signal above the noise floor. Consequently think of starting at the whole system's noise floor - including the noise embedded in the software - not the efficiency rating of the speakers to discern your dynamic range. Also remember that the power ratings of amplifiers do not dictate output. The wattage ratings serve as one measure of an amp's prolonged sustainable capability without failure.
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