I'm by no means experienced, but shall share with you what I can.
- What do I need to know about IEMS and their materials/build? Is acrylic always heavy so should be avoided if intending to wear for long sessions?
In my experience, general comfort is more dependent on the shape of the shell than the material or weight itself, although this is very much influenced by use-case and individual preference. Small shells (e.g. Sennheiser IE200; Moondrop Chu) don't present problems to most people. Small-medium shells (e.g. final A3000; Tanchjim Origin; Moondrop Kato, Softears Studio4) could already present problems because that's where the shape of the shell starts to interact with certain parts of your outer ear (concha, tragus, antitragus, antihelix, inferior crus) in earnest. Sharp angles, specific nozzle angles, shallow insertion make or break a set for people. Larger shells, in turn, usually sport a semi-custom looking, ergonomic design (e.g. Xenns Top, Thieaudio Monarch MkIII) but unfortunately, this is not a guarantee of a secure and comfortable fit. Then some large shells are just too big. Most people I heard talking about the Monarch MkII can't wear them too long or at all.
In the background of the above discussion lies the size (diameter and length) of the nozzle. Even if you have large conchas but not so wide ear canals, the Blessing 2: Dusk with its enormously wide (relatively speaking) nozzle won't work for you: fractions of millimeters matter. Lastly, another important point to consider on universal IEMs is the tip (shape, size, material) because it exerts direct pressure on your ears, quickly leading to fatigue, pain, inflammation if something is wrong.
A related image from final audio showing the pressure points of IEMs:
By acrylic you mean resin, I presume? Resin shells are usually quite light, so I don't think you have to worry about those. Some are filled (Moondrop S8), those might be heavier. Metal shells can be equally comfortable and light -- or not. The ikko OH10 is a (very) heavy set, I personally had no issue with it, for others it was a deal-breaker. Metal shells are, however, cold upon touch and could be prone to condensation, these are additional aspects to consider.
Another important consideration is venting or lack thereof. Most sets are vented, meaning the pressure in- and outside your ears is going to be roughly the same. Look for tiny holes on the shell to confirm this. Using unvented sets (usually full-BA sets, like the Softears Studio4 or the Moondrop S8) leads to a pressure difference that's quite uncomfortable to some, rendering the set utterly unusable and potentially ruining one's day.
- Are there any lists of IEMs broken up by what they excel at / target audience?
- I see many lists just ranking IEMs with no context as to what their tuning is, as a noob this isn't super helpful.
Providing detailed context in a ranking list is not very common, however,
Crinacle,
Timmy, and
Precog do provide short descriptions you might find useful.
Jay's upgrade guide could also be a useful starting point.
If you learn to read FR graphs, you'll be able to see the general idea of the tuning yourself, so there won't be a need for the description of that.
- Additionally while it's not always true, for full-size headphones if you want bass you mostly know to stay within Closed territory. Doesn't seem like the same concept exists for IEMs.
Most IEMs, whether they are vented or not, are considered to be "closed," so you're correct, this is not a variable/problem (like open-back headphones having "better" tuning, closed ones more bass) to keep in mind. Nonetheless, semi-open-back IEMs do exist, and they usually offer less isolation.
- How to figure out ear size? Pretty sure I need small tips and from what I've read Baroque and AZLA ASMR tips are a good choice.
Experience and taste in eartips are going to be unique to you and dependent on your anatomy and whether you like the way they change the sound.
The sizing is something you have to try for yourself because your ear canals are one of a kind and the size you need is going to depend on whether the set needs shallow or deep insertion. In general, shallow insertion needs larger, longer tips, deep insertion the opposite. It's best to have a varied assortment of tips. These are going to be your earpads, and are one of main elements that change the sound of a set.
Personally, I think wide-bore tips (AZLA Crystals, TRI Clarion, Whizzer SS20, Tangzu Tang Sancai, Moondrop Spring tips) are usually the best because they don't occlude the nozzle, which could lead to unwanted resonances. In my experience, medium or narrow-bore tips (Softears UC, Tangzu Tang Sancai, Dunu Candy and S&S, FiiO HS18, SpinFit W1, ddHiFi ST35, final E-type) shift the energy from the treble to the upper-mids, potentially leading to a loss of air, more forward vocals and the relative perception of more bass. Most people seem to prefer this (or prioritize comfort over sound), and some sets (like the final E and A-series) are designed with this in mind, so they sound the best with their own tips.
Tunings I'm looking for: I like midbass and subbass to be laying down a foundation in my music that everything else sits on top of which has lead me to really enjoying the Denon D9200 and ZMF Eikon as 2 examples of what I'd consider true neutral that take bass EQ quite well to get into really special territory. Something different but similar enough is the Meze 109 Pro. The king of this sound signature that I've heard is my JM XTC 2.5.
My only points of reference for IEMs are TIN T2s I got 5 years ago but got rid of 3 years ago and Apple AirPods Pro which serve a completely different purpose. These will be desktop used going into an RME ADI-2 DAC. Only other thing of note is I prioritize comfort very highly and intend to wear whatever I get for 5+ hours a day.
From what I've read so far it seems like the CA Bonneville is a semi-safe recommendation but that's also jumping straight into $1k territory and I'm positive there are less expensive and more expensive options that will be better in certain areas.
I didn't hear these headphones and going by "translating" the headphone FR graphs into IEM graphs is difficult, if not downright impossible, so I'd rather not suggest anything specific to you. Instead, I'd advise you to shop around for cheap sets (under 50 or 100 USD) that have very different sound signatures but are representative of a tuning archetype without quirky things, then listen to them with great attention on many genres, and
learn to read FR graphs. It might make sense to concentrate on one aspect or variable, for example bass. Get a lean, a warm, a V-shaped and a "neutral" set, and see which one you like best. After a while it's going to be easy to tell what you like, and using this knowledge and reviews, you can make an educated purchase at a higher price. I did it like this.
Lastly, check out
this page, it might prove to be useful.
