I agree with your review, the Luna is an impressively capable IEM and pretty close to my idea of perfection. Actually, the only one thing that kept bothering me during my evaluation was that slight upper mids glare. I listen to a lot of classical music, and orchestral pieces tend to have plenty of energy going on in that range.
So I decided to do something about it and tried out narrow-bore tips, like Sony hybrids. However, the result didn't sound convincing, so I went on to play a bit with damping. (Obviously, equalizing the 5kHz range in Neutron on my LG V30 would have done the trick too, but whenever feasible, I prefer something that works consistently with all my sources.)
In the end, I found a simple damping solution that subtly tones down the highest peaks, but leaves the Luna's overall sound signature fully intact:
(High range > 1kHz, DF-compensated) red = stock, purple = narrow-bore tip, orange = damping mod
Btw, it's easy to see why the narrow-bore tips didn't really work, they just cut down on treble extension, but left the peaks pretty much unchanged.
However, the damping mod succeeded in taking just a smidgen of energy out of the peaks, yet without taking the sparkle and shimmer out of cymbals and chimes (i.e. the 7-10kHz valley remained widely unaffected).
Here's how I did it: I used a foam filter, harvested from an old ChiFi IEM:
I cut the filter in two halves and shoved them into the Spinfit tips (from the rear side).
Fortunately, the Spinfits have a slight narrowing in their stem, which prevents the filter from sliding out at the front.
That's basically it, very easy to perform and takes some of the edge out of the Luna's upper mids. Pretty sure it will work with cotton swab as well, just in case someone wants to try it and doesn't have a foam filter at hand.
Conclusion: with its high range ever so slightly tamed, I now feel confident to state that the Luna is the overall best dynamic driver IEM I've heard to date. I've auditioned several TOTL DDs in the past, which ultimately failed to impress me: the CA Vega, Beyerdynamic Xelento, IE800S, they all left me rather underwhelmed when compared to the much cheaper JVC FDX1. And while the latter still rules (for me) in terms of bang-for-buck, I have to admit, that sonically, it has now met its match with the fabulous Dunu Luna.
So, thanks
@DUNU-Topsound for having me on your loan tour, the Luna is one exceptional IEM that undoubtedly deserves a place my collection.