I'm a little late to the party... but I read something that Currawong wrote (waaaaay back on like page 20-something now), and thought I can add a little bit of perspective which might help (at least I hope).
Quote:
...I want to comment briefly on expensive universals versus customs: I understand the thoughts on that, but I think is too general to make a statement about the price against ALL custom IEMs, as they are many and varied. Custom IEMs, as I understand it, came about as a service for professional musicians. Because they started as a special option for professionals, they were the best designs available and starting with the UE10 (or 11?) pro, the most expensive and complex*. I think we have this image in our mind that a custom fit is necessary for the best sound. Maybe it is? I think though that for ordinary people, which is most people here, for those of us in the market, high-end universal IEMs are a more realistic option. Few existed though before the TG334, K3003 and now SE846. I think the idea of top-end customs caught on because there weren't any top-end IEMs and that, in turn, has spurned a market for top-end universal IEMs. It seems to be rather like the arguments about balanced vs. ordinary amps: The only reason we argue about it is because the difference for the end user is very physically significant in that the headphones have to bee re-terminated. With custom IEMs, they have to been moulded just for us, which is very significantly different as well. If those big differences weren't there, the arguments about which is better wouldn't be there either.
So, overall, I think what people are trying to say is that with a custom IEM, one expects to get significantly better sound than with a universal IEM. It's considered a given. So the idea that a universal can achieve that is either a: something that renders a custom redundant, or b: impossible, when neither is actually the case, but more so that companies haven't tried making a top-end universal IEM until fairly recently.
*Though probably not many people realise that Etymotic IEMs, such as the ER4 have been available with a custom mould for years.
If you look back at when Shure made their first dual-driver IEM, there were already plenty of dual-driver CIEM in the industry that's been around for a quite a while. Indeed, these dual-driver IEMs were created to cater to the needs of professional musicians, thus they were the highest quality component available at the time. So I agree with Currawong that part of the reason why we often equate "custom IEM" with the "best IEM" is due to the history and legacy of IEM's development.
In the past couple of years, the line between universal and custom IEMs has certainly blurred, you cannot say for certain that any CIEM could outperform universal just because it was custom. However, there is still one very key characteristic that defines the difference between universal and custom. The magic word is "consistency".
I think we're all familiar with how much an IEM's sound characteristic changes when you use different tips. Even a small change in the way the IEM seals against your ear, or the distance that the sound port is placed from your ear, changes the sound characteristic drastically. I think most (I can't speak for them all, only the ones I know) CIEM companies strive to ensure that the output level of each of their drivers at the port opening complies within a few percentage point of variance to the specification of their design.
This becomes even more complex as you increase the number of drivers in the CIEM, because the placement of those drivers may alter just a little bit due to the shape of the user's ear. So each CIEM is carefully measured and calibrated until they're consistent. Even with all those careful calibration, none of this accounts for the last few millimeter of space between the end of the sound port to the ear drum.
So if you consider all the measurements that goes into ensuring consistency in CIEMs, imagine just how much more variance there are in any pair of universal. I'm sure everyone's also experienced the pain of matching sound signature with IEM tips, and having to make compromises between what "sounds best" and "what's the most comfortable".
With a CIEM, at least in theory, you have comfort alongside of the most consistent sound you can possibly get from an IEM. That's a differentiator against universal which could qualify custom IEM being the "best experience", even if one can debate on the relative sound quality against other universals on the market.
So if the debate comes down to whether a $1000 CIEM is always better than a $1000 IEM, we simply can't make those blanket statements anymore. However, if I was given a choice between both, where the CIEM might score a 90 on some sound test, where the IEM scores 100, I would tend towards getting the CIEM for the sake of consistency and comfort.
Anyway, back to the Shure SE846, which I think is an intriguing flagship product. They're essentially throwing aside consistency to a degree: You can change the filters, you can change the tips, and somewhere in between you might find just the right tweak to get your perfect sound. It's certainly an interesting angle, if you can't get complete consistency with your high-end product, why not just make it more customizable? I like the approach (or risk) they've taken, and being universal doesn't automatically preclude this IEM from being worthy of its price. Time will tell? Maybe?
