Speaker's efficiency, sensitivity and impedance

Chris

Efficiency is related to Watts, and Sensitivity is related to Volts.

To supplement Duke, if I may,here are some semantics. Basically,
* efficiency is a measure of how much electrical energy the spkr converts into acoustic energy (very little). It can be expressed in %: this speaker's efficiency is 5% (that high!)

* Sensitivity relates to how much acoustic energy a spkr produces given a specific amount of electrical (potential) energy.

I.e. for a "sensitive" spkr: you give it a little bit of electricity and, being very sensitive, it starts singing

So, the more sensitive it is, the more efficient it will be in the long run. I.e., if it is "sensitive" and plays very loud with very few volts, it is more "efficient" converting electricity into sound.

As you know, impedance is the resistance the spkr "system" has at 1kHz usually.(the actual res changes with frequency, hence the name "impedance" rather than "resistance"). Paraphrasing Duke above, and as a rough rule of the thumb, the lower the impedance quoted, the less "efficient" the speaker.

Chris, my ribbing was meant to be good naturedly humorous, but I think my underlying point was serious. You've spent a lot of energy trying to reduce a rather complex issue to a single parameter. Impedance is only meaningful when it is considered in combination with all the other factors.

Simply put, there is no one "audiophile" impedance that people should shoot for. It is only one of many factors to be juggled depending on the overall design goals for the speaker in question.

Chris, thanks - hope that was somewhat helpful.

Gregm, you are of course correct - the proper expression of efficiency would be a percentage, and then we could probably do apples-to-apples comparisons! I've only seen percentages given in prosound, though. Note that I used the wording "as commonly used in consumer audio" so that I could go back and weasel my way out if necessary, and I'm invoking that weasel clause now.

Duke

So, what would be easier to drive?
A speaker with 90DB and 4 ohms or a speaker with 88DB and 8 ohms?