I don't know how accurate the trends will be, from submissions to your spreadsheet; as it's the opposite of random polling.I have hinted at my issues with my pair of FDX1 and it is time to share with you and try to get a better picture of the situation.
Short history:
I have had the JVC FD02 for 8 months and modded them with some micropore tape, documented here: https://www.head-fi.org/threads/jvc-ha-fd01-class-s-solidege.868414/page-13#post-14870966
The FD02 is exactly the same as the FDX1, except of a fixed nozzle, a stainless steel driver cage and a different cable. Also in Crinacle's measurements the FD02 and FDX1 measure basically identical below 1kHz.
Based on my very positive experiences with these IEMs I ordered the FDX1, hoping for a better cable and liking the idea of being able to quickly change the tuning.
I received the IEMs about 10 days ago and noticed that the rotating mechanism is much looser than on my FD02, so much so that they would easily rotate, even when just inserting them into my ears. On one of the ear pieces a gap opened when pulling the shell parts apart. The other thing I noticed immediately was a very thin sound, with none of the nice sub bass I was used to from my FD02. What followed was a lengthy discussion with @james444 who was extremly helpful and patient, supporting me through the process.
I have a simple measurement setup with Dayton IMM-6 microphone and 3d printed coupler, which is by no means very accurate but serves well for comparative measurements.
the first measurement showed that one earpiece had a somewhat weak bass response, the other even less. The measurements looked like a leak in the shell, so I tried to find it and see if I could fix it without returning the IEMs.
I tried taping the seam of the rotating mechanism and any potential source for leaks.
The worse of the 2 ear pieces improved to about the same level as the better one of the 2 when I taped the front vent with micropore tape, which could mean that the filter behind the vent had an issue. But other than that no amount of taping any potential source for a leak showed any effect on the measured frequency response. In the end the IEM looked like this:
In the end I ran a series of measurements of my FD02 (unmodded), the 2 FDX1 ear pieces with empty nozzle and as a reference also my Sony EX800ST to have a clear picture of how the 2 FDX1 measure. I was very careful and measured each ear piece twice to verify that I had good repeatability.
In the meantime I have been in contact with the very friendly, fast and helpful from Drop, who offered me an exchange or refund.
I really want to have a good pair of FDX1, but based on my experiences and other statements in forums I am wondering if I just got unlucky or if these are wider spread issues.
Therefore I created a simple GOOGLE DOC spread sheet to get some statistically relevant information.
Id' appreciate your support to fill this in, also if your samples are good
https://docs.google.com/spreadsheets/d/1veF86mHF-A9imr9IcfDANUJIGiqpo_tug73aI_QsKbc/edit?usp=sharing
Finally my last measurement, normalized at 1kHz (App shifted curves to -25dB?)
FD02: Light blue curve "2a" - only one ear piece since both measure virtually identical
EX800ST: green and yellow - for reference
FDX1-1: red, "2e"
FDX1-2: purple, "2d"
Dark blue: artefact of the APP, didn't manage to avoid that.
If Drop were open to swapping your HA-FDX1s for the HA-FD01, that could be interesting; as it would allow you to see if the Japanese reviews (on Amazon) of the various nozzles do make a difference.
https://drop.com/buy/jvc-ha-fd01-iem
For me, the total cost would be a major factor. Would you end up paying for your respective country's import fees and taxes twice, if you accept the option, for a replacement ?
Good luck
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