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)

Obelisk, rodman is correct. The drivers have to be phase/time aligned. Sound from each individual driver has to reach your ears at exactly the same time. The Dalquist DQ-10 was the first speaker to try and deal with this. 
It is all about transient response, the ability to start and stop fast without ringing.

Boy some really odd analogies flying around here. Audiokinesis are you out there somewhere? Your help would be appreciated:)

cd318, quite a long marketing dissertation for a easily solved problem. All he says about our hearing is correct. Our ears are primarily location detection devices. They evolved to locate danger. His analysis of speakers is correct. This is the major problem for horn speakers like the K horn. The drivers are at significantly different distances from you ears.
The "easy" solution is to use one driver and no cross over. Not so easy.
The only transducer type that has been able to do this successfully is the full range ESL. Trying to do this in the analog domain with conventional drivers is difficult and only really effective at one location. At higher frequencies say the midrange to tweeter crossover it is more difficult to match things up then at much lower frequencies with longer "slower" wave lengths like a sub woofer crossover. 

Hold on Andy. That is a mistake. Yes they are all transducers but their ability to function in air is quite different. ESLs and horns are a better impedance match to air and transmit sound waves more efficiently. Dynamic drivers have to work harder to get the same results. ESLs work entirely differently than conventional speakers. First, there are no magnets. ESLs are capacitors conventional drivers are not and represent an entirely different load to the amplifier. Designed correctly their transient response is superior to conventional drivers because the moving system has far less inertia and is a better impedance match to air.
Planar speakers are somewhere in between. IMHO in spite of the compromises you have to make ESLs rule as long as you can make them. I have personally not heard a conventional speaker sound as convincing. Some say well designed horns can do it. But I am still waiting to hear one that does. 

Andy, all I am saying is that the more revealing a speaker is the more sensitive it is to defects up stream such as a miss tracking cartridge or distorting amplifier. ESLs, ribbons and horns are frequently blamed for problems elsewhere in the system. Not that some very good dynamic speakers might get caught up in this.  

Erik, yes speakers interact with the room but that has nothing to do with the transient response on the speaker.
Mike, unfortunately regular dynamic drivers are a poor impedance match to air. They have to work much harder to get the job done. ESLs and Horns do not have this problem to near the degree.
ESLs and horns are generally described as being very detailed. They also have better transient response, association or causation. I would say the later. Yes, a speaker with a lighter moving system could have better transient response assuming the motor was designed correctly. 
Andy, resolution and transient response are very closely related. By dynamic I do not mean loud. I mean snap.

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. 

simmonmoon is correct. The correct term is transient response. Speakers with faster transient response tend to be more detailed and dynamic.
There are a bunch of rather silly terms out there in regard to audio equipment sound quality. Terms like pace and timing are frequently misapplied to speakers. The pace and timing of music is set by the musicians not the speakers. More poetic waxing.