The Best Sounding Systems can Play Loudly with Low Distortion

To each their own.  I have two systems in my house.  One requires some oomph before the speakers open up and really perform their best.  I’ve run those speakers with three different amps of varying power.  I get the same result, meaning the speakers need a bit of power above what I consider quiet listening, before they really become dynamic.   The other speakers, which are in my listening room, sound dynamic at low volumes and keep it up to the point the volume is too loud for me.   Interestingly, the speakers in my listening room are supposedly not as sensitive (87db) as the speakers in the other room (96db).   It’s a mystery. 

One thing I have learned in my (relatively) short “audiophile” journey is that there is no such thing as too much headroom and I still hate tootsie pops & rolls.

85 dB is egregiously loud. OSHA wouldn't allow you to stay in an environment that loud for any length of time without ear protection. The reason your ears are ringing after a night of loud music is because your brain is trying to compensate for the permanent hearing loss you endured.

Interestingly, as the level of volume that occurs in a particular environment increases the human ear naturally and instantly becomes less sensitive to lower-level sounds and nuances, such as a fellow employee trying to talk to a coworker over the din of machinery in the background. Same thing happens in your listening room as you're try to discern the drummer's lightest brush strokes over the din of the horns in the band.

Low order harmonic distortion of the second and third variety in audio gear are naturally occurring in that humans are familiar with them in all manner of speaking whether it be acoustic music or the sounds of nature outdoors and are completely consonant with what the human ear is accustomed too. Higher order distortions 5th, 7th and 9th at least in electronics generally occur at much reduced levels and are reduced further in level with the negative feedback that gives an amplification device their gain. Intermodulation distortion on the other hand is insidious and quite audible from active electronic devices like preamps and amps and passive mechanical ones like phono cartridges and speakers. Pulse code modulation in DACs also produces significant amounts of intermodulation distortion as well as quantization noise keeping distortion levels no lower that .22%.

Dynamic driver distortion increases exponentially with increases in cone excursion. Electrostatics are limited in the amount of absolute level they can produce due to their very limited excursion capabilities. Among the ways to ameliorate the distortion issues with dynamic drivers is to limit cone excursion by horn loading them which again "exponentially" increases their efficiency and solves the problem of excessive cone excursion and reduces distortion as long as the speaker system isn't overdriven. You can also design direct radiators or baffle mounted drivers with underslung voice coils wherein the voice coil throughout it's range of excursion never leaves the magnetic gap as it moves back and forth. This requires fewer winds of wire on the former and enormous magnet structures to compensate for the "exponential" loss in efficiency and also reduces distortion as long as the speaker system isn't overdriven.

There is virtually no dynamic range to speak of at the typical rock concert in an auditorium, bar or club venue. It's just loud. If you go to a concert of unamplified classical music at the BSO, at times the SPLs might briefly reach a 100 dB in some parts of some compositions but most of the time you have to be absolutely quiet, shut up and sit still to hear everything that's going on, on stage. Classical chamber music was specifically commissioned by the elite to be played in specially designed ornate and reverberant rooms where a small group of listeners sat around a four or five piece ensemble while they played. Just a couple relative examples.

I have to agree with @ghdprentice a system that can play dynamics and full rich articulate bass at low volumes probably is just as important. 

Once you start getting up in the higher db's the room starts getting more involved so what can be a clean sounding low distortion system may sound "different" at those levels

I think the OP is directionally correct, though there are lots of good points added about having a system perform well at low volume.

I have two systems. My cabin system is in a much larger volume room that is better constructed and vastly more acoustically inert. I intend to build room treatments to improve things further, but it is already much better than the 2nd system even though the components are of similar quality. 

Though I usually listen at moderate volumes in the cabin system, I will periodically find the volume higher than expected when someone wants to talk and I have to turn down the volume to speak with them. There is an effortlessness and ease at any volume that the 2nd system lacks.

The 2nd system resides in a living room I am unable (unwilling) to treat. While the components can play much louder without stress, I cannot listen at anywhere near that volume as the room becomes too active. It’s adds audible distortion. As a “system” (room included), it’s much lower performing than the cabin system. Indeed, I’m considering selling the entire system because it is so much more satisfying to listen to the other one. I spend more time there, too.

So I would generally agree that being able to reproduce dynamics fully is indicative of a better system. It’s certainly not the only requirement as fidelity to signal, full range, imaging, and the ability to have the speakers “disappear” are even more important to me. But a system that can’t scale dynamics effortlessly is surely indicative.

For reference, I primarily listen to jazz, classical and acoustic folk though I do put Pink Floyd and the like in rotation.