Neutral, transparent, warm

So, I find Harbeth to be slightly warm yet very natural/transparent. However I do not find it "Fast". I had Totem and KEF speakers and listened to many B&W's and found them to sound 'Fast" - but can I describe 'Fast" for you? Perhaps Lively is closest. I would suggest listening to as many speakers as you can and you'll eventually find adjectives that work for you.

For instance, I didn't understand a 'grainy' sound said about DAC's until I had heard enough of them and suddenly I heard one that sounded 'grainy". 

I don’t know if it’s still available, but at one time Stereophile offered a little pamphlet containing all the terms used (some coined) by the father of subjective reviewing, J. Gordon Holt.

Neutral and warm refer to frequency balance, transparent does not. Think of transparency like the pane of glass in a window between you and an object on the other side. If the pane of glass is absolutely transparent, removing it will in no way change your perception of the object. If you then install a not-completely transparent pane, the appearance of the object will be effected, to one degree or another. One effect can be the glass changing the color temperature of visual images passing through it. That is analogous to a loudspeaker being cold or warm---not neutral

A way to simulate the effect of transparency and lack thereof is to take a camera with an adjustable focus lens, and alternate between perfectly focused and just slightly out-of-focus. When perfectly focused the lens appears to be invisible---the image "tack sharp"; when slightly de-focused the image of the object becomes softer, a little "diffused" or smeared. In worst cases texture or grain will be added to the surface of the image. Also, the de-focussing can reduce your ability to see depth-of-field (front-to-rear layering, as in a symphony orchestra on a stage), and objects can be smeared together. All these visual terms, concepts, and observances apply equally to the high-fidelity reproduction of music.

If a loudspeaker isn’t perfectly ’neutral" (none are), it will change the "color temperature" of instruments and voices; it will change their inherent timbre. Since all loudspeakers are short of perfectly neutral, hi-fi consumers must pick the coloration they find least objectionable. That’s why loudspeaker preference is so subjective. Many audiophiles---while appreciating the transparency of ESL’s---find them a little "cold". ESL fans find dynamic speakers too warm. It’s been this way for a long time, and probably will for the remainder of our lifetimes.

In the early days of hi-fi (post-WWII and into the 1950’s)---when dynamic loudspeakers were really bad---audiophiles were astonished when they first heard an ESL design (the QUAD ESL hit the market in 1957). I know I was. The ESL’s sounded far, far more transparent than did boxed speakers (this was before Jim Winey in 1970 introduced his Magneplanar loudspeaker, itself a planar-magnetic design). Dynamic loudspeakers have been greatly improved over the past 6-7 decades, but ESL’s still sound more transparent (imo) than almost all box speakers. Magnepans are in the middle, still not as liquidly-transparent (a JGH-coined term) as ESL’s..

And then there are horns and ribbons. ;-)

a speaker i tried for a bit [then put back into their shipping boxes] was a vandy 1Ci, in the oversized demo room of a local dealer, they sounded very 3-dimensional [utterly non-boxy if you kept your head in a vice] and warm yet sufficiently clear, run from a rega amp [which doubtless added to the perceived warmth], utterly non-harsh. but when i tried them in my 14' wide by 14" deep listening room, they sounded obnoxiously bright and forward and shouty while simultaneously veiled [driven by old jvc 130 wpc amp]. a disappointment. was told i needed twice the listening room size and another rega amp to duplicate the dealer's experience. no thank you. enter my gently used set of Thiel cs.5 speakers, about half the size of the vandys. the Thiels combine all 3 [aforementioned] attributes. it is the warmest-sounding of all the other Thiel speakers, the only one that can be driven satisfactorily by non-audiophile non-powerhouse amps and the only one that can be used in a small listening room. these speakers are neutrally transparent and image solidly, while the vandys did not, in the same listening room with same amp driving them. the only other speakers i've heard with my own two ears, did not quite have all three attributes in one package. the maggie tympani IIIs were transparent, neutral, but not a trace of warmth. never harsh, just ease and a cold accuracy and images that floated in the room regardless of listener position. no other speaker i've heard could do all that. back in the 80s i heard KEF 105.2 speakers in a fancy schmancy dealer in DC, they were also transparent, neutral but not warm at all. later that decade i heard the revised Snell class A speakers, in a room slightly too small by about half, they were decidedly warm but not KEF-level transparent and not KEF-level neutral, but i could easily have lived with them. i remember they had a visceral deep bass. 

all this reminiscing aside, transparent to me = being able to hear deep [all the way to the back of the recording venue and all around it, from FFF to PPP and everything in between, hearing in between the notes] into the recording without any haze or hash or resonance getting in the way, IOW low distortion. neutral to me means an announcer's voice sounds like you are in the announcer's booth with him, no shriek or boom or overhang/resonance, just clean accurate sound with the same tonal balance as the real thing. warm to me can mean both a bias towards the lower half of the frequency spectrum esp. below about 2k, but also a lack of strain, an ease, a sheer clear naturalness of sound that ties in with transparency and neutrality.

New Duntech Audio Senators and the new Fink Team Borgs are some of the most transparent box speakers on the market. Very Quad like !

Oh yeah, I forgot some of JGH's other analogies about transparency:

In addition to the term "veiling" (thanks for the reminder emrofsemanon!), he likened lack of transparency to a layer of "scrim" (must be a term from before my time, but I get it) being inserted between listener and source.

A quality important to me in the sound of reproduced music that is closely related to transparency is that of "immediacy"---the images being "palpable", as in "reach out and touch it". Another is "forward" vs. "recessed". I think that may be more a function of frequency response than transparency, but the two are not completely separate.