I thought I'll contribute something too. So here is a bit about our TBA-04.
My rig measurements:

Note that it's CSD, not Burst decay like Purrin uses:

And that's factory measurements:

I will not go into the detail about sound, as my opinion may count as biased.
Reminds me some vintage full-range speakers, I did not hear similar signature in any other earphones, but I not tried all of them Not neutral for sure, but quite pleasing. Best sound for me is with westone yellow foam.
I do not hear that 4.5kHz dip. Also, CSD may appear as ringing, but its not really bad. May appear with some eartips, and be non-existent with others. And looks better if use Burst decay graph