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

regismc, a fast cable? Please don't make me choke on my dinner. Electricity travels at the speed of light. All wires have exactly the same speed. Resistance and capacitance are separate issues. Personally, I would rather be addicted to sex. (Big smiles from the wife)

 As much as I have enjoyed reading through this thread, I couldn't help but remember when Velodyne made subs that used an accelerometer on the woofer cone, allowing it to be 'corrected' by the sub amp 3,500 times per second (maybe that is the way they still operate, dunno). It has been a very long time since I have owned such an animal, but I still remember the speed that I heard in the bass. To me, it came across not only in impact, but pitch definition as well. 
 Years earlier, when I owned a pair of corner horns, the bass had much of this kind of quality too, IIRC. 
 The sub that I am using presently (10" driver with a 12" passive radiator) with a velodyne SMS-1, doesn't have these effects, even though the bass is enhanced (increased).

By the way, horns use conventional drivers so they are probably the same.

surroundings which hold cone and magnets(alcinico,neodium) usually is different

The TS parameters for bass driver being used in a horn is very different from the same sized driver used elsewhere. For example, the surround of the driver is much stiffer (typically a cloth material), since the cone moves very little. +/- 1/16 was amount stated in the horns that I made. 

jeez, I thought this had been fully debunked 

from 1978 (High Fidelity magazine), article by Mark Davis, AES Silver medalist for technology and product achievements at dbx and Dolby, an MIT PhD in EE/psychoacoustics:

// ... a transient is a signal that happens fast, but only once. Generally observed on oscilloscopes and sometimes photographed, transients are usually supposed to look "clean," without any visible ringing or overshoot. By now it should be clear that we are concerned not with how a waveform or response looks on a scope, but only with how it sounds. Like any other signal, a transient is a collection of frequencies. In order to preserve the sound quality of a transient, the speaker should have a flat frequency response and less than 2 milliseconds of phase shift. Since the latter requirement is easily met, it follows that transient response will depend primarily on the flatness of the frequency response. Looked at another way, a transient's deficiencies of sound must be the manifestation of a departure from flat frequency response. Therefore, if one measures frequency response, the measurement of transient response is essentially superfluous.

I was just reading REL sub website guff about driver 'speed'. Wow. Audio mental feebleness is on the march again.