Sorry, I missed this. Two areas find the modded FD01 wanting are bass dynamics and detail, and sound stage. How does the NM2+ fare there? Looking forward to your expanded comparison!
So, a few things about my FDX1 that I wasn’t thrilled about include a “shouty” upper midrange, centered around 4 KHz, that needs mods to help tone down, a poor overall fit (though it can be worn with cable over ear or straight down, but I don’t like the rotating shell design), and lack of impressive soundstage/imaging. The main strengths to me include excellent timbral accuracy, great detail retrieval and resolution for a DD, and a neutral-ish tuning (I actually quite like the cool tonality).
In comparison, the NM2+ maintains or improves on all of these strengths and addresses all of these weaknesses. Despite the looks of the graph, surprisingly, I don’t find the NM2+ shouty. It is almost at my personal threshold, but doesn’t reach it. I’m actually quite sensitive to prominent upper midrange frequencies, so if I can tolerate, and actually enjoy the upper midrange on the NM2+, I think most people will be able to tolerate it as well. No mods needed IMHO. I really like the shape of NF Audio IEM shells. They have long nozzles, but I find that this makes them capable of both shallow and deep insertion. I don’t myself constantly fiddling with these IEMs to get the angle of the nozzle correct, when there are no fixed landmarks, as is the case with the rotating FDX1 shells. It is important to note, however, that the insertion angle of the nozzles and ear tips is important, and one has to find the optimal angle for the best tonality and imaging. The NM2+ shells are very lightweight too.
The imaging is exceptionally good for a single-DD IEM. Instrument placement it accurate and well defined. Soundstage size seems above average, though I’m not good at assessing this. Instrument separation is very good, even during complex passages. It’s not quite as holographic as the best multi-driver IEMs, but it is one of the best I have heard from a single-DD IEM (perhaps tied with the ISN D02?).
Timbral accuracy is exceptional for acoustic instruments, the best I have heard yet. I would consider the tuning to be neutral-ish, though the bass is slightly boosted from true neutral, which is great IMO. I don’t find the tonality to be warm or cool, but really quite neutral. The FR dip around 7KHz doesn’t seem that noticeable to me. The only minor criticism I have of the NM2+ so far, is regarding the bass. It seems more mid bass biased. While the sub bass extension is excellent, it seems to be less than the mid bass. The bass on this IEM is fast and really punchy, with great dynamics, but I apply a little EQ, to boost the sub bass a little, and cut the bass some at 100Hz. This seems to make the mid bass a little less boomy, and quite a bit cleaner. The bass is never muddy though, even w/o EQ. Overall, the bass seems a bit more prominent on the NM2+ than on the FDX1, though the bass is more sub bass biased on the FDX1. While the bass is not as dynamic or textured as beryllium coated drivers tend to be, I think the bass sounds more nuanced, and this definitely has DD bass, with nice rumble and decay. Lastly, the speed, accuracy, resolution, and micro detail retrieval is the best I’ve yet heard from a single-DD IEM. This doesn’t take away anything from how good the FDX1 is, but the NM2+ is just a little bit better, especially with detail retrieval.
The NM2+ is a very impressive IEM IMO, and is especially superb with classical, jazz, instrumental, acoustic genres, as well as with female vocals. While I think it can play all genres of music quite well, R&B, rap, EDM are not its strong suits (I have not yet tried taping the back vent to boost the bass though). The NM2+ could be great with metal, depending on one’s preferences. The driver is very fast, detailed, with great transient response, which is necessary for metal, but I personally find the tuning a bit too intense for a lot of metal, at least at loud volumes.
While I personally love the tuning of this IEM, it is certainly not for everyone. It depends on one’s music preferences, and this is not a universal, all-purpose recommendation.