I've been using the NDH30 for almost 3 months. Here are my thoughts:

Comfort and build

I like how they look (I'm one of the few who still prefer the silver version over the newer black one). They feel like a premium product. The earpads are one of the most comfortable with a 65mm inner diameter and around 22-27mm depth (22 in front where the driver is, 27 behind the cloth where the ear is). I like how soft the velour material is - I'm very sensitive to itchiness and I don't have any issues here. I also find the shape and softness of the foam to be perfect for my head and ears. And the clamping is on the looser side but it's tight enough for the secure fit. I don't feel like they're going to fall off. They're pretty light (367g) with decently large earpads so you don't really need much clamping for the stable fit. They have also very good ergonomics. I'm probably weird but I actually like the cable being on the right, because I also have my amp on the right side of my monitor. And I like that they can fold flat - useful for cleaning the earpads. Although, I would prefer them to fold in the other direction.

I have only 2 complaints:

1. The headband padding is not very good. It's alright from the beginning but in longer listening sessions I can feel those 2 spots on my head. Not that it's stiff - it's pretty soft actually, but the contact area is so small it doesn't distribute the weight very well. It reminds me of the DT900 PRO X. I also don't like that there is rubber on the sides of the headband.
2. The cable is pretty bad. It's too long, a bit microphonic, a bit stiff, and the termination is really bad - it's covered in rubber so it feels really cheap and the adapter to 6.3mm won't stop screwing. You can screw it infinitely. So sometimes I have issues with sound cutting or rather sounding weird and then I realize there is something wrong with the cable and I have to play around with the termination to get it back. At this point, I found the position where it works so it didn't happen for a time now, but still pretty annoying. The worst thing is that the hole for the cable on the headphone is really small so the M40X cable won't fit. So I got used to the stock cable. I mean, it's not the worst so it's still usable.

In terms of isolation, it's what you would expect from a semi-open headphone. They're slightly more open than K712 or DT1990 and DT900 PRO X, but more closed than most open-backs. That also doesn't help when it comes to cable microphonics. It reminds me of X2HR in this regard. I don't have them anymore to directly compare but I remember them also being less open and having clothed microphonic cable.

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Sound

They're about as hard to drive as HD660S2. Or at least they sound about as loud on the same volume with a linear source.

The overall tonality is solid but not perfect. When I was reading about them, I was really confused because some people were complaining that they were too dark and some that they were too bright. Now I understand why. The treble is a bit unbalanced - the lower treble is emphasized and there's not much air in the upper treble so depending on the content you're listening to, they can sometimes sound too dark and sometimes too bright. But most of the time, they sound relatively neutral.

I also read that depending on the position on your head, the treble will sound different. I tried to move them around and while yes, when I put them completely back or completely in front I can hear a difference, but that kind of fit is very uncomfortable so why would anybody do that? While wearing them normally, I couldn't notice any difference when moving them around slightly. Also, because of their design where pads are deeper right behind the driver, there isn't really any more space where you can move them before making it uncomfortable. So I wasn't able to reproduce this issue on my head, or at least not in realistic conditions.

I would describe their tonal balance as Harman-neutral. There's quite a lot of bass for not being a closed-back, they're a bit too bright in the lower treble and too dark in the upper treble. So they sound a bit shouty, glaring, harsh, tense, and fatiguing because that lower treble is always in your face while there's not much sharpness in the very top end making them kind of sound like behind a blanket.

NDH30 on Gras (Oratory) against the preliminary target until we get the correct DF

against Meze 109 Pro

against MM-500

against HD650

against HD560S/HD400 Pro

Their presentation reminds me of DT1990 by having a very intense kind of sound but also with that sense of contrast. They sound lively, engaging, and pretty detailed like they want to force all the details in your ears. But it doesn't sound sibilant, for the most part. You get that underlining thump from impulsive low-end and snappy transience from the transparent lower treble.

Spatial qualities are also what stands out on them. They don't have the best soundstage or the best imaging I've heard, but a very good combination of both. I would compare them to R70X or K712. You get that surrounding kind of experience which is pretty satisfying. They have also a very good sense of depth and scale. Only when the tonality doesn't work for the content they can get a bit claustrophobic and focused because of that tension.

Use case and conclusion

They're not my favorite for busy music because of that harshness, but where they really stand out is orchestral/epic/OST music. I also like them quite a lot for hip-hop. But they also sound pretty good for anything that can use that extra sense of contrast, like rock and metal. I just need to always "recalibrate" my brain for the brighter ear gain. The vocals are also very good. Not as good as HD600 but pretty close. Most importantly, they have that "ethereal quality" when it comes to instruments. Especially the pianos and orchestral instruments. Some people were comparing them to ZMF headphones so now I really want to try the Auteur Classic :)

They're also pretty good for competitive shooters. Not my first pick but one of the best for sure.

When it comes to immersion and ASMR, I find them too harsh and fatiguing for both. They're not bad, just not what I would use.

If you didn't know, NDH30 uses the same driver as HD560S, so there are some similarities in their sound, like the spatial presentation and some tuning features, or that intense kind of sound. But while I'm not a fan of 560S, I'm really impressed with the NDH30. It's a good example of how the driver itself doesn't mean anything. It's about how it works together with the acoustics. NDH30 is basically what 560S was supposed to be.

NDH30 is one of those headphones that made me think about selling most of my collection when I first heard them. Now I know that there are flaws, but even after a few months, it's still one of my favorite headphones. Although, there is one headphone I sold because of the NDH30. I finally found something that took the K712 off my throne for orchestral music. I tried so many headphones but there was always something special about K712, so they still held their position as my favorite for that kind of music. Until I tried NDH30.

I can highly recommend the NDH30.

Some examples of what sounds the best on them:

Queen's Gambit OST

Battlefield 1 OST

Joker OST

Game of Thrones OST

Metro OST

this kind of music

Recently, there was an Audeze sale in my local shop so I could get these for 670€. I wanted to try them for a long time so I finally gave them a shot. I've been reading that they are less resolving but more neutral than LCD-2C, which is also what I would say about M1570 in comparison to LCD-2C, so I was hoping they could replace my M1570. Both LCD-GX and LCD-2 Classic are the latest 2021 versions with open-cell pads (the OG version had memory foam pads).

DISCLAIMER: I was writing it like I would talk to myself so when I say for example that headphone A is more comfortable than headphone B, I really mean that I personally find it more comfortable. Everything I say is just my impression I just didn't want to write "IMO" in every sentence.

Comfort

So far, the LCD-2C has the best ergonomics of any headphones I've ever tried. I always thought that LCDs with magnesium chassis were the same in this regard. So considering the GX is even lighter than 2C (457g vs 530g), I was expecting them to be an improvement to the already comfortable 2C. And for the most part, they are the same. The same headband, the same cable, and the same pads, but there is one thing that completely changes the way they feel. Different yokes.

Yokes on the GX have a more aggressive angle and more aggressive offset. That results in a lot tighter clamping and most importantly, most of that clamping is shifted in front of my ears. So whenever I pitch my head forward, the headphones will fall off. Even when I don't pitch my head, headphones will slowly slide forward until there is a gap behind my ears. It feels really awkward wearing them. Because of that aggressive angle, the rods connecting the yokes and the headband are now larger and I need to extend the headband more on the GX. Also, because of that angle, the headband doesn't hold its position but wants to open up all the time so I have to constantly close it to my size (which is 5 notches on the GX and 2 notches on the 2C as shown in the picture).

Also, the back side of the spring steel is sitting on my head because of the aggressive offset. And one last thing, the yokes are now also bigger because they're rounded so when I want to adjust the headphones on my head by grabbing the yokes, I can barely stretch my hands around them because they're so large. None of this was an issue on the 2C design. I can barely notice the weight difference but when it comes to ergonomics, it's really bad on the GX while on the 2C it's the best I've experienced so far. Overall, I find the GX a lot less comfortable.

LCD-GX 2021 vs LCD-2C 2021

more aggressive headband offset (tried to align them with cups)

more aggressive yoke angle (tried to align them with rods)

2C yoke angle when stretched around the same length

GX yoke angle when stretched around the same length

longer rods on the GX - if they weren't longer the GX headband would be too small to fit normal heads

2C vs GX on the smallest headband position - GX would probably fit a cat when stretched

this is how the 2C headband sits on my head

this is how the GX headband sits on my head - btw I have a very average head

Practicality

GX is easier to drive (gets louder on the same volume) than 2C.

In terms of isolation, there's about as much of it as on the 2C, but I would say it feels a bit more closed in the higher frequencies and more open in the lower frequencies. Both are somewhere between open and semi-open in terms of total isolation.

What I don't like about 2C is an aggressive pneumatic effect, so it feels like wearing a closed-back. I can hear every movement, cable is microphonic because of it, and I can even hear my own breath and heartbeat which is pretty annoying. I don't get this issue on the GX, or at least not as much as on the 2C.

GX comes with an extra boom mic cable which retails for $180. The mic is pretty good. Sounds better than most integrated mics but not as good as the dedicated FOX mic I use. The boom mic cable is terminated with CTIA wiring where the mic and ground are inverted (common in China). But there is an adapter that fixes it to OMTP wiring where the ground is on the sleeve and the mic on the ring (common for the rest of the world - works with Apple dongle, phones, or any other amp). There is also a splitter if you want separate jacks for headphones and a mic. The splitter is wired for CTIA input so you should unplug the adapter first.

Sound

When compared to 2C, the GX has a more linear midrange which results in more cohesive imaging.

Unfortunately, it comes with a big cost of treble being very dull. It's not just slightly less detailed, it's a lot less detailed than both 2C and M1570. I would say it's competing with headphones like M1070 or Verum 1.

In terms of dynamics, it's still one of the more interesting features of LCD-GX but in comparison to other headphones for less money, it's really nothing special. M1570 or Verum 1 are more engaging than GX. I guess it's mostly because of that dull-sounding treble that makes everything sound compressed. It still has pretty good transience in the midrange and still sounds somewhat large, but it lacks that tactile feeling from the treble.

The soundstage feels a bit more intimate than 2C. I guess that could be also because 2C sounds generally more U-shaped so it feels more distant and more separated between left and right. I don't find 2C to be particularly spacious anyway. The soundstage is decent but nothing special. Comparable to something like Sundara.

The bass is similar but less noticeable and less textured on the GX.

Imaging, while being better than 2C, is still nothing special tbh. I tried them for competitive fps and while I didn't have spatial distortion like with 2C, I didn't find GX to be very competitive. Pretty average.

So all in all, LCD-GX are IMO very average-sounding headphones and that's the biggest issue considering how expensive they are. There isn't anything that makes them special. Anything interesting that's better than on other headphones. The best thing about them is that they don't sound offensive in any way. Their tuning is pretty casual and they're OK in every aspect. But there are cheaper headphones that are also OK...

Comparisons

LCD-2C is more detailed, more dynamic, more spacious, more neutral (general midrange to treble balance), and more comfortable, but also more U-shaped so they can get a bit too sharp at times and their upper midrange is a bit too dark and distant. That results in slightly unnatural imaging where you can't tell if something is in front or behind.

M1570 (lambskin pads) is more detailed, more dynamic, more neutral, and more comfortable (despite being very heavy at 689g), but the midrange is slightly less linear. Spatial qualities are similar.

Verum 1 is more neutral, more dynamic, more comfortable, and with better imaging, but the soundstage is slightly smaller. In terms of detail, they're fairly comparable.

M1070 (lambskin pads) is more neutral, but slightly less resolving, less dynamic, and there is a hole in the upper mids. Spatial qualities are similar. Trading blows with comfort.

Avantone Planar is slightly more detailed, significantly more spacious with a lot better imaging, but probably even darker and less comfortable than GX. Hard to compare the dynamics since Avantone is a bit rolled off in the sub-bass but more present in the mid-bass. I would say it's similar but different.

Thieaudio Phantom (without front foams) is significantly more spacious (probably even more than Avantone), and a lot more explosive, but less detailed and has a very weird tonality so it's brighter and more muffled at the same time, which results in inconsistent imaging.

HD660S is more neutral, more detailed, and with better imaging, but has a bit smaller soundstage and worse low-end.

HD660S2 is even more neutral, even more detailed, and with even better imaging, but still has a smaller soundstage. Low-end might be better on the 660S2. Feels more punchy for the very least.

Use case

I tried all kinds of genres of music, competitive shooters, ASMR, immersion, everything, and I really struggled to find anything that would sound impressive on the LCD-GX. It doesn't sound bad, but it didn't impress me at anything. The best experience I had with them was for immersion while watching some movies. But in the end, I still preferred M1570 or HD660S2 which are both cheaper.

Value

Even if there wasn't a boom mic making LCD-GX cheaper for $180. And even if it was on sale for 670€ like I bought them, I still don't think they're worth it. They are competing with headphones in the 200-400€ price range and they're more than twice as expensive...

Conclusion

As you can probably tell by now, I am very disappointed with the LCD-GX 2021. They aren't bad and I could enjoy them with certain content on lower volume. But I would expect this kind of experience for a lot less money.