Let's expand on this a bit. Here are some random reviews where the author casually introduces the term
microdynamics:-
"
Excellent microdynamics....better microdynamics into lower impedance loads..." - Genesis reference amplifier reviewed on 6moons
"..
.the microdynamic changes within musical passages that constitute a musician's phrasing were somehow more clearly defined than with most other amps I've heard....the Berning's microdynamic capabilities made these continuous variations in their instruments' volumes very easy to follow....Recordings high on boogie factor were propelled forward with a huge kinetic impulse. Microdynamic nuances were given full scope of expression...... Feelings and emotions are buried in the music's microdynamics. The Berning had no difficulty at all in retrieving the music's full emotional gamut." -various Berning amplifiers reviewed by Soundstage Ultra (Vade Forrester) and TAS (Dick Olsher).
"..
the company reworked the existing Lavardin design for greater linearity, which improves overall transparency and microdynamic resolution."-Lavardin ISx amplifier reviewed by Alan Sircom.
"
If this technology sounded any different from a good analog amplifier, tube or solid-state, it was in its transient and dynamic performance. Both were both stunning, especially in the rendering of bass microdynamics....I don't think you'll be less than impressed by its micro- and macrodynamic performance, by its rhythmic swagger and ease, by its exceptionally solid imaging, accomplished transient delivery, or overall coherent sonic performance." -Sharp SM-SX100 integrated amplifier reviewed by Stereophile (Michael Fremer).
"...
there was remarkable sensitivity to this recording’s microdynamics. Vengerov’s vibrato was as easy to hear, and in several sections I was surprised to hear slight changes in dynamics that I hadn’t before." -Genesis Reference GR180 amplifier reviewed by UltraAudio.com (Albert Bellg, probably influenced by the manufacturer's constant promotion of the product's microdynamics, all quoted extensively in the review)
"...
the resulting sound is big, powerful and meaty but without sacrificing the nuance or micro dynamics in delicate recordings....the MHA200 just kept "revealing the true nature of every headphone, without adding anything of its own. And it does so with power and punch but without sacrificing on the subtlety or micro dynamics." -McIntosh headphone amp reviewed by What Hifi?
"
Yes, it can thunder when the music demands, but it's just as adept with the internal drama and microdynamics of an Andante un poco moto." -Rotel amplifier reviewed by Hi-fi News (Andrew Everard)
"
There is some penalty for the extra devices and complexity (compared to a single-ended direct-heated triode amplifier), that seemed to be one of the trade-offs here: a penalty on microdynamics. Likewise, this amp isn’t as immediate as simple tube amps. It still has immediacy, but not on the level of the finest tube products. I could say the same thing about really big tube amps: not as much immediacy or micro-dynamics—very simple amps can do some things quite well." -Sanders ESL amplifier reveiwed by Dagogo (Phillip Holmes)
"
So there is proper tonal saturation and perfect micro-dynamics and resolution." -Plinium Leonidas amplifier reviewed on High Fidelity (Wojciech Pacuła)
"
Feedback levels much above 20dB, aside from stability issues, appear to constrain the soundstage as well as compress microdynamics....The Carver had a slight edge in dynamics from soft to loud, though both amps fell short in terms of microdynamic conviction relative to a good SET amplifier, at least in the context of a high-sensitivity loudspeaker." Z-Infinity Z120F power amplifier reviewed by TAS (Dick Olsher)
"
Microdynamics
MIT Terminator 5...many faults...most of all, a definite loss of ambient detail. This is rather striking in low level listening, as fine musical nuances seem lost, and the music comes across as rather flat and lifeless. Sort of like listening to public address system, the volume is there, but there's no finesse.
Graham Slee Cable 1...Soundtracks came alive, detail was restored to a high degree, and most important to me, the passion was indeed there. Fine nuances could be heard, something I don't expect to happen at this price, ...
VDH D102 MK 3...this cable can deliver almost anything that is in the program material, leaving my KA-i180 to deliver it to the speakers. The point here is, this cable can transfer the emotion in and behind the music, the fire in the music which is all too often lacking elsewhere." -3 interconnects reviewed by TNT Audio (Dejan Veselinovic)
"...traits such as microdynamics were increased, separating the apparent volume between instruments and voices occurring simultaneously. In a word, the Accusound interconnects sounded like I could hear more music, as they revealed the intentions of the musicians, engineers and producer behind the performance more easily." -Accusound XD interconnect reviewed by Enjoy the Music (Tom Lyle)
"And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made. But in the afternoon he became restless for he saw that some improvements are necessary for Ethernet (audio) cables to satisfy humans... Through the AudioQuest Vodka the Rochat’s cello was firmly locked in space, slightly left to center. Its timbre was rich and assured, with fine microdynamic resolution and vibrant textures. The blast of orchestra that arrives at 2’ mark was natural and uncompressed, and the close-miked finger-plucked strings were like gunshots through the TAD speakers. It was easy to sit back and enjoy the depth of soundstage with the soloist playing just for us. When the Vodka was removed and replaced by the OTSC the sonic gap between those two was heard right away. The sound collapsed to become sketchy and one-dimensional. What was previously heard as rosin on a bow became merely a wiry sound. The transparency and bloom of the orchestra transformed into undistinguished mass, we were not able to detect any individual instruments within it." -ethernet cable shootout reviewed by audiodrom
OK I'm back. Random reviews but not of random components. I focused on amplifiers and cables. Why no speakers? Because I want to make a point. When these same reviewers above, and countless others, go to review loudspeakers, they will write about the microdynamics of the speakers, just like they did above for electronics and cables. From their point of view, they are talking about the same perceptual quality when they talk about microdynamics, no matter what the type of gear. So let's not kid ourselves: just because some here can imagine a somewhat-plausible mechanism by which a loudspeaker might exhibit a greater or lesser amount of 'microdynamics' (which is still horribly-loosely defined by most people as "whatever I can imagine it might sound like if the words Micro and Dynamics were mooshed together (word of the day mooshed courtesy of MakeMineVinyl)"), and let's not forget that I have described just yesterday in this thread a few flaws such as frequency response failings that could conceivably be a somewhat-plausible mechanism by which a loudspeaker might exhibit a greater or lesser amount of perceived 'microdynamics', but just because you (or I) can imagine it for a loudspeaker, I bet you are going to struggle a lot more to justify its appearance when listening 'to' decently-engineered amps and cables.
So like I said, let's not kid ourselves: when sighted subjective reviewers, including ourselves, say we hear more or better microdynamics from a component, it is generally imaginary (MattHooper will never believe this: read his dozens of thousands of words in other threads defending the writings of sighted subjective reviewers as being legitimate descriptions of the sound wave differences), or misattribution, and that's a fact. And with loudspeakers, even though they do sound detectably different, I will wager heavily that in almost every single instance, any non-imagined difference is simple misattribution, where maybe something simple like frequency response imbalances have made it sound a bit clearer in one band, and we leap to call it microdynamics, when in fact the speaker is not in any way able to make small changes in amplitude more accurately within the large 'macro' scale of music.
cheers