Just like on any playground -- there is a divvy where the kids choose up sides.
First cut: You are in the *Do No Tweeking of EQ* as an "homage" to the engineering and artistic group(s) who produced this captured performance in the hopes that they had *any ideas* about acoustical engineering beyond the simple passion for their musical inspiration of the moment -or- you are not and fiddling with as many controls as you can find is part of the experience in pursuit of whatever sounds best to you as a technological support for *your* interpretaion of the artist's captured or realized performance.
Second cut: You are in search of audible information to the limits of your hearing as a personal test of ability -or- you are examining the technology used to capture the performance being served up today to put "your system" into a condition to "transport" your mind into the acoustical experience of the artist, via your ears.
At base, and acoustical transducer (speaker, cans, IEMs) is a pump or an impeller delivering a wave of kinetic energy to your body via some fluid medium where your nervous system will perceive it as motion, impact, tone, etc.
Properly driven with suitable power and a clear analogue signal any Etymotic 4- series, or Etymotic 3-series will exceed the hearing range of any human -- ANY, human. How "flat" it is is debatable ans subjective unless you are considering a microphone that has been calibrated ( and the concatenations and possible system ramifications from this point of departure are probably endless ).
The current XR vs SR debate has more to do with personal preference for a simple rig with fewer controls -or- the best use of available power in an under-amped system -- usually a pocket-portable one.
The next major issue is fit & comfort. I have slightly narrow but deep ear canals that do not match -- left compared to right.
I fiddled with flanges and foams and plastic chemistry for several years until a made a DIY casting of both ears and sculpted out a recess that any Etymotic barrel I have: HF5, up to and including ER4XR -- fits nicely. As these also fit my ears with no pressure and what is essentially a perfect seal. The only remaining comfort issue was sweating behind the seal and I have adressed that elsewhere.
Unless you are in the first tranche listed above and will accept no EQ adjustment, then there is no better IEM you can buy since with enough power ( not really that much ) and a clean signal your ears can't go beyond the garden variety of sound produced by a clean Etymotic barrel.
I adjust my system regularly and have recorded the varied settings as the have evolved over the years.
Inherently, no 'can' nor IEM will FULLY reproduce the listening experience of "live" music ( nor nearby thunderstorms ) nor reproduce by whatever music media file a "large" PA offers, in the visceral sense.
Of over-the-ears cans I replaced/modified the cushions on one pair of NAD-Viso cans with real leather cushions that allow for more space for the auricle during protracted listening sessions. These offer pretty good isolation but lack the "air" & "staging" I find in open-backed Sennheizer cans.
An unintended consequence was a better conduction of low frequencies to the skull bones allowing for nice deep bass energy to be delivered to my head -- Submerge by Phutureprimitive on the Subconscious album, among others, has low end signals that are quite pleaieng, as well as Symphony No. 3 in C Minor, Op. 78, R. 176 "Organ Symphony" composed by Saint-Saëns: performed by Jan Kraybill, Kansas City Symphony & Michael Stern and SUPERBLY captured by Keith O. Johnson (engineer) and David Frost (producer) -- the whole album is just stunning!
One experience involving an extended, outdoors, listening spectacle, several years ago was provided by 8 speaker towers arrayed in a circle about 200 feet in diameter. When *suitable* music was played the dirt in the center of the circle jumped from the gound in time to the beat. This is the sort of visceral experience I set as the standard for "Visceral" -- yes, just about everyone had earplugs in. The sound impulses were readily experienced as compressions on one's thorax.
I speculate that at some point I will find a bone-conduction transducer that might distantly approach something like this.
I use digital file test tones to measure different listening systems and to monitor my ears sensitivity at -10dB standard volume and rough-in an EQ curve using these files when I am calibrating my experience. Then I proceed to a short list of Recording Artists with stringent standards of performance capture. Not limited to: Joni Mitchell post 1976, Steely Dan post 1976, Dire Straights Brothers In Arms, Trilogy 2 by Chick Corea-Christian McBride & Brian Blade in HD is just wonderful...
Clearly I am an equalization proponent. A side hobby is remastering and in some cases significantly modifying the dynamic range and EQ of vintage recordings or other "what the hell were they thinking" performances of many artists. Deep Purple is a great example of cool music indifferently recorded as is early ZZTop. The "sound-wars of the late 1980s and 90s are good eras to find music steam-rolled flat dynamically. Not every poor choice can be elevated to what I like.
The engineering premise is to move air with precise alacrity by some surface that is driven as accurately as can be managed by amplified current. Lower mass surfaces need less power. Lower volumes of air need less power. The minuscule "pump" moving air in the Etymotic IEM achieves this nearly as well as mountains of massive coils in enclosures driven by tons of amplifiers or electrostatically driven gossamer membranes ( I'm thinking STAX Headphones, here driven by Class-A Macintosh Amplifiers of the 70s vintage ) striking the air to produce compression and attenuation waves that we might hear.
Stick with your Etymotics. Improve the play-back engine/software you use for digital files. Upgrade your DAC. Acquire personalized ear-casting inserts for your Etymotics. Selectively purchase better source materials -- minimum 96/24 HD files. Review your interconnects and dust in your contact points. Reduce the processing burden of your playback platform when you are listening critically while being disconnected from the interweb -- background OS-bloatware diverts resources from the best you can get from your system. I Do Not Stream. I am sitting next to 30-ish tB of hard drives and use optical-drives for many things. Look for untoward latencies in your system. If I need portability I have a veteran iPhone 6s I now use as an 'iPod' -- the app I like best for IOS is *EQu* and for OSX is *Fidelia*.
Keep Reaching!
