Neutral or Detailed. You can't have both

erik,

To be clear:  My argument was a sort of "in principle" argument.   My example was using real life sounds as the stand in for "neutrality."   An acoustic guitar played life is, in this sense, experiencing a "perfectly neutral" sound, in the sense no additional artificial distortions are being added by anything.   It's an ideal of what a truly "neutral" system could re-create, which suggests neutrality is not in opposition to experiencing fine detail at low sound levels.   So, in principle, "detailed sound" and "low levels" are not at odds.

I hope that is more clear.

(Though they *are* at odds in some psychoacoustical sense, insofar as our hearing apparently perceives more detail/higher end detail as sound gets louder.  But even granting this, I can still experience a finer sense of detail at low sound volumes from real life sounds, vs through most speakers).

As to real world examples, I'm not sure I would be able to come up with any that satisfy you.   I do remember the Waveform Mach Solo speakers retained a satisfying sense of detail at low volume levels, as do a pair of Waveform Mach MC (egg head unit) monitors I still own.

Some measurements for the Mach Solo here:

http://www.audio-ideas.com/reviews/loudspeakers/waveform_mach_solo.html

My bigger Thiel 3.7s also seemed to retain fine detail at lower levels.

Monitor audio speakers I auditioned a while back, too.

I'm not sure if there are really very many speakers out there that everyone could agree on (even speaker designers/enthusiasts) as being "totally neutral."  It seems there is always some departure from neutral that can be found in measurements, that someone will point to.

I've thought about this and I mostly agree.  Most musical instruments are fairly loud and most recordings are made with microphones fairly close.  It makes sense that a speaker that is neutral would have the full detail of the instrument when played at the same volume as the instrument.  If listened to at a much lower volume a lot of the detail will become inaudible.  I definitely think some speakers manage to retain detail at lower volumes better than others.  I don't know what the factors are.  I suspect low mass, stiff drivers are better at making small transients audible.  

I have two systems, one with Thiel 3.7s and another with ATC 110s and I love them both but they're distinctly different in that the Thiels are better at low volume while the ATCs excel when cranked.  The ATCs sound boring at low volume but they are capable of far larger dynamic swings.  

I would think that at moderate listening volume, a neutral sounding speaker, as the human ear is concerned, would have a measurable dip in the upper mids/ lower treble. I believe this why the average studio monitor leans toward brightness and fatigue.

I agree that exaggerated treble is often mistaken for detail. Case in point would be Golden Ear Tritons:
https://www.stereophile.com/content/goldenear-technology-triton-one-loudspeaker-measurements
They have quite a large boost above 10kHz. To my ears, these speakers produced about as much detail as $400 Klipsch towers, yet they were ear-piercing bright. Maybe the brightness was simply masking detail?