What does the term "Speed" mean in a speaker?

Another way of talking about "speed" is "lack of stored energy."

I supposed that has more to do with "driver break up" or suffering from "impedance anomaly".  Paper cones may have a clean water fall plot, but an aluminum cones may have "faster speed" but may not look as clean on the water fall plot.  

Of course having "faster speed" does not always mean "better".  There word "speed" in this thread seems to have a lot of different interpretations.  Different people seem to have different impression of the word.

Now I get. The view perpendicular to the revolution is opposite except in  the downward position.  

i think speed in a speaker mostly refers to the mid and upper bass 50hz-250hz region which are the power frequencies where the music lives. vocals, drum kits, pianos, cellos, horns.....they all fall down or rise in this area.

leading edge precision and the presence or lack there of ease and refinement in these frequencies either impart flow and energy to the music and maintain the timing or muddle and restrict that flow and energy.

this is a speaker-amplifier-room issue, not just the speaker. and typically you see a crossover right here, amps struggle controlling the drivers here, and rooms have most of their worst bass nodes in this area. as you increase the dynamics and SPL’s this will be where things go to hell first as the combination of the speaker’s limitations, the amp and the room acoustics all rear their ugly heads.

but get the crossover out of this region, have sufficient driver surface to limit the need for much excursion, and appropriate amplifier for the speaker draw, solve the room issues, and you can get the ease and effortlessness and the speed and precision of the music will result in that speed that serves the music, the music breathes and soars.

Has anyone heard Martin Logan speakers? The electrostatic panel plays the mid and treble while the woofer plays the low frequencies.

I always felt like the woofer was slightly lagging behind as if the bass and the upper frequencies were playing slightly different tune.  The bass was in effect "slower" vs. the mids and high frequencies.

Also, most of the time, speaker frequency responses are measured in steady-state response which more or less erases the transient response, but the "speed" lies in the transient response.  So two speakers can have the same freq. response but one may be faster than the other.

May be a step response measurement can tell you the "speed" of different speakers because it preserves the transient information.

Mass and inertia guys. Transient response is how fast the driver starts and stops. Lets say you have 6 inch speakers with identical voice coils and magnets. In one the cone weights 1 oz and in the other the cone weights 2 Oz.  When I play a transient sound like a drum stick hitting a steel plate the 1 oz cone will start moving fractionally before the 2 oz cone because it has less inertia. It will also stop faster with fewer oscillations (ringing). Things are really more complicated as the Transient response of a driver is not only determined by the mass of its moving system but also by the power and damping capability of its motor. So an 8 inch woofer does not necessarily have better transient response than a 12" driver. Speakers with better transient response have a crispness to their sound missing in speakers that don't. This becomes quite evident when listening to ESLs, well designed horns, ribbons and to a slightly lesser extent planars. Speakers with better transient response are more revealing and can easily be made to sound crappy with bad or poorly set up equipment which I think is why some people have a jaundiced opinion of them particularly horns which are also not easy to design.