To add to the DD conversation. If I'm not mistaken, the way a DD is designed is a diaphragm that actually moves air and decent amounts of air. BA driver's don't.
So expecting a BA driver to be able to reproduce the Kick and low end pressure wouldn't be as feasible. I'm not perfectly aware of the components and functionalality of drivers but as I know it, BA driver's move a thin diaphragm back and forth between two magnets at a rapid pace in a small space not moving much air. While DDs use electromagnetism to move a larger diaphragm using coils in more space which creates more air movement.
As an audio engineer though I can comment on part of why this possibly is, DD better for low frequencies.
As most know, low end frequencies around 20hz and such we actually 'feel' rather then hear. We are also accustomed to vibration in our bodies with certain powerful sounds. The lack of physical feeling is apparent in BAs because they're not moving air to give enough space for vibration and physicality. Also, low end frequencies are large sound waves, they require more space (air) to fully complete their wave cycle and more energy to move the diaphragms to reproduce certain powerful low frequencies. If there isn't air being moved as much, low frequencies - even if reproduced sound wise - will lack physicality due to lack of air. This is also noted by our perception missing out on our memories of how low frequencies vibrations feel to our body. Air vibrating at certain speeds are the frequencies that then are interpreted as sounds, the lower the frequency the more air and space needed. The less air you have, the less the lower impact/physicality will be reproduced.
Also, the comment about the kick drum impact should all be done in the recording stage.. this is obviously the point. We do focus on this if were recording for it and desire that sound. But we're using microphones with the ability to record the sound and air actually being moved by the drums and then we're using speakers that hear what is recorded and mix and master from - that DO have large diaphragms being moved and reproducing that air. So we're mixing and mastering with that sound apparent the whole time. We make sure it's there. But if you're listening to a recording that has all those things inside the recording and the gear you're using doesn't reproduce the same air movement or even produce some of the same frequencies - no matter the recording skill - you're not going to hear it the same way because your driver's not capable of reproducing It. So yes, we record all these things in the mix, but if your gear cannot reproduce it, it's not the fault of the engineering.
This is not to say a BA cannot have good low end. They can. But what they're doing is reproducing a sound/frequency that their given, without the actual air there. So it's a reproduction of the sound kind of like what it imagines it would be vs what physical space actually would produce from analog gear. This is similar in comparison to the analog vs digital debate. It's not that digital isn't amazing, digital can reproduce sounds amazingly, but without the actual physical dimensionality and space and air being effected you will lose that same effect and sound signature that analog gear actually creates in physical space. Not to say one is better then another. They're just different.
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.
This makes sense. When speaking on my desire for the kick drum to be palpable or produce the proper impact, this comes from wanting as close to life like performance as I can obtain. Many see reference tuning as an uncolored point of reproduction and I have seen many times conflicts about bass level, response or quality because of IEM's that produce bass as it would actually sound right in front of you. So, to me, that would be more correct of a reference point due to the mere fact that some drummers beat the snot out of their pedals and some don't. That alone would make something appear heavier than normal in the mid bass punch. That doesn't mean that an IEM or headphone recognizing and putting out this frequency is improper or out of reference.
That's why I typically judge the accuracy of an IEM by certain things I can easily reference in person, often with drums or guitars. I know how a china or high hat sounds in person... same with snares and heavier percussion drums. So when I hear an IEM that doesn't do this properly but everyone says it's reference, I raise an eyebrow. I am in no way saying they are wrong, I am saying my place of judgement differs for those reasons.
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.
The term reference is an interesting one. Reference in relation to what? The actual recording? The instruments? Or some predetermined 'gold standard'? Ask 5 people what they consider 'reference' and you'll probably get 5 different answers.
Same goes for the term 'accurate'. Accurate compared to what? The instrument as recorded? The instrument as heard in the studio? A bar? A concert hall? How do we determine accuracy? And if there's no measurement of accuracy, isn't it all subjective anyway?
For me, reference and accurate are interchangeable. They collectively mean the reproduction of the frequencies recorded as closely matched to that recording as possible. So all the bits are in the right place, so to speak.
What reference doesn't take into account (for me) is the physical aspect of some sounds - like kicks from a real drum or strums from a real guitar. That physical air movement by the instrument is something we've all felt before, not just heard.
That's why playback from a BA IEM may well be more 'reference' or 'accurate' waveform for waveform, but that doesn't mean it will feel as real or life-like as a so-called coloured or non-reference rendition of the same track on a DD IEM. It simply lacks the physical aspect of the sound as played by a real instrument (or as reproduced by dynamic speakers, which is how we experience sound at a live event).
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.
