Fast is another adjective for transparent, it has to do with the apparent speed of the transients. Usually lighter sounding gear is reffered to as fast, whereas warmer sounding gear could be reffered to as slow.
Get a copy of the rodrigo y gabriela self-titled CD/DVD and if those extremely fast guitar licks sound crisp and clear your system is "fast". If it sounds somewhat blurred, vague, or muddled, your system is "slow".
But one word of caution... on some systems (especially if you're using a tube preamp and the phase is inverted) it will sound slow, vague and warm... until you reverse the speaker polarity and then it might sound fast and focused if your gear is up to it...
I hope you're thoroughly confused now. Happy New Year!!!
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.
Fast should mean quick transient response, but nothing can be taken out of context: you can't, as audiophiles do, find a fave word and run with it. Fast could mean an amp with a high slew rate, then someone will point out that some amps with a low slew rate sound terrific. Do you judge the beauty of a women based solely on, let's say, the nose? A system is a chain of many components and each component is the result of many choices or compromises. To say that fast means transparent gives pretty short shrift to distortion and noise.
"Fast" is only part of the sonic story, but an important part I think. It might be easy to confuse the term "Fast" with "Bright" and "Slow" with Dull". I think the later comparison is stronger than the former. I agree with the previous posts that my definition of "Fast" is the ability of a system to accurately reproduce the leading edge transients in music. My view is that getting leading edge transients "right" is a joint effort from source to loudspeaker, but seems to have its greatest test within the amplifier.
My limited experience is that solid state and some digital amps can be very good at leading edge transients, but can have a harder time handling harmonics and trailing edge decay. Cheaper digital amps and sources can sound "Fast" and exciting at first listen, but reveal artifacts or sins of omission in the overall reproduction that on closer listening turn out to provide an overly "Bright" sound, lacking body, natural smoothness, sustain and decay.
Conversely, tube gear, especially older versions, can be syrup "Smooth" and "Sweet" but doesn't always get the attack altogether right. Nowadays, the more you spend on tube or transistor gear, generally the less these artifacts impede on the sound in either direction.
So "Fast" is and important aspect of reproduced sound, but not by a long ways the only important aspect.
I agree with all the above. Fast would not exist if there were not a lot of "slow" or warm gear around. So like Good is only good becuase of Evil - so it is for fast.
Essentially it is abnissue from the combination of dynamics, transient response, damping and frequency response presentation.
Over damped or critically damped speaker designs will not tend to sound slow as they do not add any oscillations to the signal (they follow the drive signal and stop moving when power is removed) The problem with these designs is that overdamped has a low bass response and needs EQ boosting to get a flat frequency response. Critical Damping is often selected as it has a nice flat frequency response and gentle roll off, however it too has an early roll off in the bass. (Unfortunately underdamped designs are extremely popular because they are easy to drive and produce copious bass - these tend to sound "slow" or whatsome might describe as "punchier" and you do get teh advantage of copious bass in a small box)
Dynamics are what stress the amplifier and speaker system. (Transducers extend to the limits of their linear travel and voice coils get hot and lose sensitivity to the drive signal, all while more power is demanded from the amp) When the system is asked to do more than it can handle in a linear fashion you either get clipping (harsh sound in SS, or warm harmonics in the case of tubes) or you get a dull distorted sound from the speaker itself, as it compresses the sound... in either case, briefly the dynamics are not properly reproduced and you have a "slow" sound and at high levels a noticeably distorted sound.
Transient response. This is linked to damping but also to driver time alignment (phase if you like)...a well time aligned system will not sound "slow" or "fast" ...just correct. Remember that the "slap" in the kick drum is at 4 to 5 Khz whilst the "bottom" sound of the kick drum is between 80 and 100 Hz. Alignment between the arrival of these signals is important if you are to correctly perceive all forms of percussion (it is much less relevant for non percussive instruments...however - be warned even the piano is a percussive instrument and will not sound correct on a "slow" system)
Frequency Response - taking the same example as above of a kick drum. If you attenuate the 4 to 5 Khz region then your kick drum will sound less "fast" or snappy - less "slap". Conversely if you augment this region then the kick drum will sound "fast".
In essence this means that through microphone placement, type of microphone (tube amplfied or not), tuning of musical instruments, the manner in which instruments are played, the use of an EQ/compressors in the mixing session, a "fast" or "slow" sound can be created on the source material. Your speaker frequency response will also influence this.
If you have a "slow" system then nearly everything will sound slow or slower...tracks will sound more alike than on a "fast" system becuase everything is colored towards "slow".
If you have a "fast" system then individual tracks will tend to reveal their individual charater more accutely => that which was intended to sound "slow" will do so and that which was mixed to sound "fast" may even sound "clinical".
Example: Steely Dan sounds nicest on a slightly "slower" system as a "fast" system will tend to reveal that just a wee bit too much audio engineering is going on...and you can hear it....the sound is dry, mechanical, clinical and almost hygenic to the point of being "germ-free" (drums on some tracks were edited and a "perfect" drum pasted in for every actual drum sound such that it just repeats and repeats identically (like an electronic drum machine but with a human controlling the timing). They used Yamaha NS-10's as nearfields in those days...so perhaps it sounds perfect on a speaker of that kind of quality. Nevertheless it sounds good on nearly any speaker, even "fast" ones.
Example: He's got all the Whisky - John Martyn will tend to sound slow on any system....huge resonant plodding bass and slurred lyrics to add to the intended effect.