This is something I discuss in my upcoming A18s review. Its low-end drops slightly as it reaches the sub-bass, which means it won't have that visceral, physical, bone-conducting effect. But, at the same time, with that rumble out of the way, I feel like the sound, colour or tonality of instruments like the bass drum come through more clearly, which makes it more ideal for EQ or tone-shaping. Whereas, if I wanted to more accurately level the sub-bass or check for phase in those regions, I'd go to an in-ear with more presence there like the JH Audio Layla. That's been my experience, at least, when using the in-ear for mixing.
I tried writing paragraphs of text agreeing to and disagreeing with several of your points, but after half-an-hour and several deletions at four in the morning, I think enough is enough.
All I'll say is that it heavily depends on your definition of what
reference means, and I'll outline mine below. But, to leave with food for thought, I think comparing an IEM's rendition of a track or instrument
directly to how it sounds live would mean skipping the recording, mixing and mastering stages entirely. There's an incredible difference between what we hear in a room vs. what several microphones "hear" up close to the instrument, and mixing and mastering is a long,
long road to getting one to sound as close as possible to the other. And, that's not to mention the
intent of the producer/engineer making the record. They might not even necessarily want the instrument on their record to sound like the real thing. Going back to your beater example, perhaps the drummers
did show tons of dynamics when you're hearing them live, but who's to say they didn't all get compressed in the mix? Or, heck, get replaced entirely by triggered samples? Also, it's vital to remember that they're all recording, mixing and mastering their track to their
own references too.
With that said, though, I do agree with your overarching point that real instruments are about as reliable as references can get. I do think proper context is needed to use them in that way, but I find it
far more universal than, say, a specific speaker or headphone. And, there are also aspects to headphones and IEMs that make them more "life-like" or "realistic" than others, whether it be the physicality and structure of instruments, the impact and verve of the lows, etc. Whether or not something is closer to
reference because of that, I think, is ultimately up to the individual and, again, their definition of
reference.
I've talked about this on another thread, but, to me, determining whether or not an IEM is
reference-grade (or transparent) is as easy as seeing how well it can... well,
be transparent; how much colouration it imparts onto the track vs. how much of the track's innate
colour it's letting show. And, I think the simplest way to do so is to play two different tracks, from two different genres and two different mixing-and-mastering styles on the same IEM, and seeing if any distinct commonalities are present between them.
For example, if I played Kendrick Lamar's
Alright and Sarah McKenzie's
Paris in the Rain and I hear a similar amount of low-end prominence, then that in-ear obviously has a coloured (or not-reference) bass response. My personal test for the upper-midrange are two consecutive tracks from Tom Misch's
Geography album:
Lost in Paris and
South of the River. Though you might think two consecutive tracks from a single LP would have fairly-identical mixing and mastering, these two actually show subtle differences in the saturation and timbre of Misch's vocals. A transparent IEM should be able to pick up on those differences. For the low-treble, I'd go to Royce da 5'9"'s
Godspeed and
Dumb off of his
Book of Ryan record. There's a difference in articulation that could imply a different mic being used or a different EQ. Either way, some IEMs are better at showcasing
all of these difference than others, and those are what I'd consider to be accurate,
reference IEMs.
I do agree with your point that the
reference label nowadays often ignores dynamics and physicality, which I think are crucial in defining an IEM's sound. If every track I listen to - from
naturalistic classical to
processed pop - showcases the same amount of dynamic range, the same forwardness to instruments, etc., then I'm not listening with a wholly-reference monitor. If a drummer plays a single-stroke roll across toms pre-panned from left to right (like Tommy Igoe on The W.I.M. Trio's
Funky Riot) and I lose the toms (or their punch) at 10, or 12, or 2 o'clock, then it's not an accurate imager of a monitor too. I think it's important to distinguish
tonal accuracy from
spatial or
dynamic accuracy, especially because the effects of the latter are more-often-than-not more subtle - yet just as crucial - as the former.
So, to me,
reference doesn't necessarily mean how close an IEM sounds to something else, because - as you said - everyone's
something else will be different. And, again, every producer will make their track with a different reference or aim in their mind too. Personally, I think the measure of an IEM's transparency or accuracy simply boils down to how well it can get out of the way. If it makes every type of horn sound honky, or every snare crackly and thin, or every male vocalist hoarse, then it's safe to say that it's a coloured in-ear monitor. But, if you can go from one track to another without noticing trends or hallmarks - whether tonally, spatially or dynamically - then those are the in-ears I'd confidently call
reference.
