Sean makes an extremely important point - EMF is a crucial factor in amplifier-speaker interaction and it is often ignored.
When it comes down to it sensitivity is really not a very useful specification at all. Impedance, capacitance, and back EMF tell you much more. Impedance and capacitance are easily measured and graphed. Back EMF is not as straightforward but it's pretty easy to tell if a speaker is pumping it out in large amounts or not from listening tests. Because Back EMF feeds on itself, and the louder you play, the more you are generating, it's a really important factor in loudspeaker-amplifier matching.
For more info see an article we wrote:
http://www.symphonysound.com/articles/tubefriendly.html
When it comes down to it sensitivity is really not a very useful specification at all. Impedance, capacitance, and back EMF tell you much more. Impedance and capacitance are easily measured and graphed. Back EMF is not as straightforward but it's pretty easy to tell if a speaker is pumping it out in large amounts or not from listening tests. Because Back EMF feeds on itself, and the louder you play, the more you are generating, it's a really important factor in loudspeaker-amplifier matching.
For more info see an article we wrote:
http://www.symphonysound.com/articles/tubefriendly.html