As promised, here is an update on the DUNU IEMs, for those needing to (or wanting to) replace their Monster Turbine Coppers with something else. I'm now the proud owner of a replacement (working!) pair of DUNU DN-1000 and also a pair of DN-2000:
Left to right: Monster Turbine, Monster Turbine Pro Copper, DN-1000, DN-2000.
The DN-2000s come in a more luxurious packaging:
Oddly, there weren't too many other differences between the DN-1000 and DN-2000. The earbuds are a little different, but both have the same (very thin) non-replaceable cables, reminiscent of those on the original Monster Turbine headphones. Neither model comes with a volume remote or microphone on the cable.
There was one surprise. The replacement (sealed, working) pair of DN-1000s also came with a pair of bi-flange tips that were not in the box of the previous DN-1000s, or in those of the DN-2000s. Here they are:
These bi-flanges seem to be exclusive to the DN-1000.
Just for comparison, here are M.E.Electronics' bi-flanges.
And here are Monster's bi-flange tips. Note the smaller bore.
In summary, I really like the sound of both the DN-1000 and DN-2000 headphones. I thought I slightly preferred the sound of the DN-2000, but that may simply be expectation bias. The DN-2000 appears to have a marginally better attack and decay, but I honestly couldn't hear too much difference. I wouldn't be surprised if I failed an ABX (not easy to achieve here, because the DN-2000 earbuds have little metal tabs, so you can feel the difference - these tabs are actually a bonus for the DN-2000 model, as you can tell left and right earbuds apart in total darkness). The FR curves aren't worth plotting, because you won't even see a difference between the two DUNU models. So, in terms of sound alone, I would recommend whichever is the cheaper (the DN-1000).
Their sound is a little V-shaped, and I agree with the left side of that V
I want an IEM that slightly compensates for the fact that I won't feel the ground reverberating beneath my feet when listening to a heavy, driving bass line. But both models also have a notable treble peak at 8-9 kHz. Depending on genre, personal preference and personal audiogram, some people will hear this as bright, clear, revealing, etc.; others might hear this as too bright, harsh, or even tinny. I've learned to live with it and tame it, when necessary, with software such as the excellent Pencil EQ in CanOpener. Their clarity is on par with that of the Monster Turbine Coppers - all three models have comparably-low total harmonic distortion. Bottom line - I really like the sound of the DUNUs. It reminds me a lot of the sound of the old TF-10. A V-shape always makes for a pretty exciting sound
Just be aware that you're not getting an identical Monster Turbine Copper sound signature with the DUNUs. The DUNUs and Coppers are much more similar in terms of appearance than they are in terms of fit or sound.
My last warning about the DUNUs is about ergonomics. I had more luck with the above bi-flange tips than I did with any of the other DUNU tips. However, oddly, they weren't included in my DN-2000 box. I was able, with some persuasion, to get the Monster silicon tips to work with the DUNUs (triple- and bi-flange), but it was hard work and the seal would easily break. I had no luck with either foam or gel Monster supertips - the DUNUs require an airtight seal of the ear canal, which the supertips aren't designed for. The tips that work best for me are the Comply T500, but even these require too much effort. I find myself re-adjusting multiple times to get a good seal. The problem with these thick posts is there's hardly any space left for foam between the post and your ear canal. This is the DUNUs biggest failing, IMHO. Any IEM that requires a good, airtight seal needs a long, thin post. The DUNU posts are too short, too wide, too smooth and require tiny little metal spacer rings that fall off far too easily and will be prone to getting lost. If you can make these IEMs fit, you'll probably love them, but be warned - these are fantastic sounding headphones with horrible ergonomics. I don't think they'll be replacing my Coppers as my go-to IEMs anytime soon, but I will persevere a bit longer with the DN-2000, because I do enjoy their sound. If you need to replace a lost/broken pair of Monster Turbine Coppers, either DUNU model would be worth checking out.
Thanks once again to oldmate for the tip on the DUNUs.