From how I'm reading the stars:
- While the IE900 extends slightly lower the Darks Sky is slightly more mid-bass focussed. (Un)fortunately you can't tell from the charts the quality of sub-bass and sub-bass so it's most likely down to preference.
- The IE900 seems to have a milder difference between male and female vocals while the Dark Sky might border shoutyness on female vocals, and likely be less unforgiving with s and t sounds, hats, etcetera.
- I think the IE has quite some brightness up top as well, but both have ample compensation in low frequencies so it may be balanced out just the way you like it.
- You're not likely to hear the 15 kHz peak on the IE900 as being excessive.
In general (and a huuuge FWIW):
- Single DD IEMs are either notoriously hard to tune from the upper-mids and higher and/or driver limitations are playing a part, often with softer materials not extending far enough (early treble roll-off: Zen) and harder materials often being a bit brighter/harsher up top (noticed by some but definitely not all in FD7 and Turii).
- I can probably safely claim that nobody on this rock has read as many IEM reviews over the past month as me, as with zero access to any IEMs preparing is all I could do. I tried to make those reviews educational reads though and because I was wondering whether looking at FR charts would provide a shortcut for my pre-selection process, for every single review I read I ALWAYS had Crin's charts open in another browser window to see whether I could see reviewers' remarks being backed up by the charts. Since for myself I'm allergic for having anything too much (think bass boosts, forward/shouty vocals, treble boosts, and any very apparent cut-outs including early roll-offs) after perhaps reading 500 reviews (?) I have learned that on average reviewers are discounting IEMs when the FR starting at 1 kHz hits above Crin's target curve at any specific place. When reading 10 reviews for an IEM 7-8 reviewers would have similar remarks about those "offenses" while for 2-3 of them it was absolutely perfect. With myself striving for avoiding "anything too much" if I see charts like for the IE900 or Dark Sky I lose interest (possibly too soon), while a Zen Pro would stay on my research list. Remember: I'm extremely limited in being able to audition anything for the next half year and may have to go for a blind buy or wait until eternity. As such I want to avoid as much risk as possible. This is completely different to most of you here, so while I have taken IEMs off my list based on charts alone YOU don't have to do anything absurd as this and simply listen, listen, listen.
- From the same "research" I think I have learned that Crin's charts have meaning between 200 Hz and 1 kHz as well but in a different way. First, crossing his target line sub 1 kHz from reading I think will lead to lesser allergic reactions. But how far the actual FR is above/below his target is all relative to what happens in the bass and treble. First I thought that if the FR was below his target note weight and body would be greatly influenced, but that doesn't seem to be the case. I'm sure it can be but it doesn't seem to be a rule at all and is depending on how the tuning is balanced out over the whole range among other things. For the mids I have noted that if sub-bass rolls off quite fast around 200-250 Hz and then stays flat until 1 kHz this more often than not is associated with very clean and detailed mids, while if the mid-bass extends all the way to 400-500 Hz before coming down the sound is often considered to have muddied mids. Again, this says absolutely nothing about quality. I mean, look at the Traillii that comes down very late from mid-bass to mids and apparently one of the best regardless. Another great example calling this exercise pure BS is the UM Mason FuSang which has an exceptionally slow roll-off from mid-bass to mids of which I might have said it can't even sound nearly correct. Turns out it has some of the very best mids possible! So be careful with reading too much into the mids.
- Sub-bass and mid-bass are very different to read from charts as well. From reading I think I have found out for myself that if sub-bass hits more than +5 dB over Crin's flat target it will most likely be too much for me and I think I would be happiest with a +3 dB bass shelf in the sub-bass, followed by a slow roll-off to that 200-250 Hz range. Also BA bass seems to be quite okay with a +5 dB max while a DD setup might be too much already even though they measure the same. I assume this is because of note weight and decay but I'm quite possibly wrong on this. While when setting out I mostly focussed on Crin's target for sub-bass and mid-bass as well I now tend to think that such a reading is not supportive enough to reach a truly engaging sound because of the lack of weight and balance. Mind you: Reference monitors might have a much leaner, faster, and more correct bass because of this (their raison d'être after all), but whether that's enough to create a "complete" reproduction across the FR that is still consider musical I'm not so sure any longer.
Repeating myself once more: A FR chart tells you exactly NOTHING about the quality of the presentation. But you may be able to spot potential allergy issues and then read up a bit to see whether that's confirmed by people of whom you know where they come from reference-wise. And still you may disagree with their assessment because of different sonical preferences, other music preferences, other allergies, the rest of your reproduction chain, etcetera.
All in all I think reading reviews, staring at the star-- sorry, charts, reveals that as a group we're not exactly crazy and on average quite nail it. But that perfect average may not reflect your preferences at all and become useless because of that. Still very educational and it leads to great interaction with people that are in the same boat, even while most likely being on a different course.
drftr
