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

Speed = Rise and Decay

I enjoy a fast midrange/woofer/subwoofer and cabinet design, as it sounds crisp and accurate. 

Tweeters are generally fast. I enjoyed the Focal Tc120/90 series tdxt with the vented pole piece, as you could build a rear enclosure and affect the sound/speed of the tweeter like other drivers in the system. 

Listen to the Bass Line in Glad Tidings by Van Morrison.....

Does the whole song sound in sync or can you sense some lag ...

Speed as a function...

Small floorstander, Castle Conway III, intel Nuc, Benchmark Dac pre, Mystere PA, you want ‘speed’, transient attack, dynamics with decay, openness?  Try Captains Audio Envy cables.  I’ve a pr. of the Studio Prestige rca, a usb, & a balanced cable.  Remarkable spacious detailed resolution, the fastest cable I’ve heard.  Lightweight, easy to handle, affordable, speed.   

Example... the Castles r bottom ported adjustable thru spacers to various room sizes.  With AE interconnects, ports wide open, they sound like sealed boxes, absolutely no overhang, spacious, neutral, dynamic, textured speed unleashed thru the speakers carbon fiber drivers.

Addictive.

Same thru a pr. of 1SC’s.  AE interconnects r FAST, and one can easily appreciate such thru the additional frequency range moving beyond the monitors.  Fun too.  Refined, cohesive, spacious, they convey a distinct ‘house sound’ that reminds of a good modern tube amp, or a great set of headphones, the small Castles sound like lovely dark electrostatics with better dynamics.  
Speed indeed...

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).