It's just a random picture of diffraction. What I mean is sound doesn't 'like' to travel down echoey plastic tunnels, I think the CK10 might use Titanium but I don't have a picture or blueprint of the nozzle.
It will depend on the matter, having a metal nozzle isn't always going to give you substantial gains, tuning of the driver itself is a lot more important. I would dare someone to take out that damper on the CK10 and see if the nozzle is truly metal inside, if anything a replacement damper can be bought and placed inside.
The FR, THD and IR are only important if you're looking for an IEM with flat FR, low THD and fast IR decay........ I'm not sure if that's all we're actually looking for in an IEM.
That's the whole point of using better materials, to reduce resonance which will result in a more even response and low THD, etc.
Even if two IEM's have identical THD levels, or one is higher, or similar impulse response, perhaps they just have different time envelopes
http://en.wikipedia.org/wiki/ADSR_envelope#ADSR_envelope, overtones or harmonics, which in turn result in a different and unique tone in each one..... after all there is no perfect IEM in THD, IMD or IR.
Overtones and harmonics are of the recording, the IEM's work is just to present what's given. Sure an IEM does add a tone as purity is impossible, but the parameters are mostly set by the main criteria in FR, THD, etc. in trying to get close to the source as possible, that's fidelity.
If IEM's all had perfect IR, perfect square waves and 0.00001% THD, IMD... well then they'd all sound nice and transparent, open windows to the recording without any tone of their own (apart from the soundspace size and related 3D perceptions), in reality they all sound slightly 'different' and we can't really anlyze 'how' they sound different.
That's assuming perfection, which isn't a reality, even stuff with very outstanding technicality can be slightly different because of certain small characteristics. We can realize how they're different, one just has to analyze every detail.
Here is an example, lots of THD and choppy square waves -
http://www.innerfidelity.com/content/hifiman-re-262-and-re-272-ear-headphones-measurements, neither graph relates to human perception, and neither graph can
tell me the differences between the RE262 and RE272
Which makes perfect sense, since graphs like that can't really
tell me the difference between a clarinet and flute either, only
show me a nonsensical difference.
Sure it can, they share the driver but the RE262 has more laid back midhighs and treble, focuses more on bass and midrange. I can deduce that by just looking at the FR graphs, HRTF will relate it to human perception. If you can't make sense of it, that's another matter, if you're expecting it to tell you how you will perceive the sound and all the subjective factors involved, you're making ridiculous requests.
