Itball,
Plato and John are quite right to my mind. Sometimes there are music bits in a given composition,which seem to come out of nothing and dissapear again just as quickly as they have come at high speed. You might compare this with a sudden snap of a whip, a sort of cutting sound often, which comes and goes in a split second. This happening is called a "transient" and this happens when the sound arises out of nothing and then decays into nothing. A system is "fast", when this sort of thing reminds one of the real thing, just as Plato has pointed out.
Mind you though, a system which is nothing but "fast", would be unnatural to our ears. Because in music you might need a fast transient as the note appears and a slow decay of the note, as it disappears and then again, just the other way around might sound right. So you see, it is a complex thing. A good system should be able to do both and to do justice to all the shadings between slow and fast at the same time, without sounding harsh, distorted or unnatural and it should be able to do this with loud pieces of music just as much as with soft pieces. Calling a component "fast" is often enough sales talk, even though perhaps justified, because the fastest component will be slowed down by the slowest component in a system. Therefore in my opinion it is better to judge an entire chain from source to speaker to find out if it sounds right or not as far as the question of "speed" is concerned.
Cheers,
Detlof
