Dunu Luna - Beryllium Dynamic Driver IEM

Copy+Paste from Dunu:

Over the years, DUNU has accrued a ton of experience building earphones and drivers; a few years ago, we reexamined our core technologies and thought long and hard about how we could make a major contribution to the high-fidelity audio space. The result is LUNA, the culmination of nearly three years of dedicated, intensive research and development. Akin to the Apollo program, the development of our new flagship was tantamount to a moonshot project, acting as a galvanizing force behind much of DUNU’s technological progress and evolving design language over the past couple of years, beginning from the second half of 2017.

So what makes LUNA special and why was it so challenging to develop? It starts with a diaphragm material made from pure beryllium.

Beryllium is believed to be the ideal speaker material. Historically reserved for applications related to aerospace and medical fields, the metal was identified to be exceptional for sound reproduction by way of several of its intrinsic properties, beginning with its extremely high stiffness-to-mass ratio (high Young’s modulus, low density). It allows beryllium to possess a very high speed of sound of over 12,000 meters per second, around two and a half times faster than other commonly used cone/diaphragm materials like aluminum. The very low Poisson’s ratio of beryllium potentiates its ability to maintain pistonic motion of the driver, even at the edges of a diaphragm, and in turn preserves the imaging properties of the music being reproduced. The very high Debye temperature of beryllium also means the lattice structure of the beryllium metal is retained even at very high frequencies, translating to remarkable treble evenness. All these unique properties of beryllium enable audio designers to gain extra octaves of clean, non-distorting, non-ringing, high-resolution sonic output at both ends of the sonic spectrum.

This reputation of beryllium as a wonder material for audio has translated to a bevy of products made to contain beryllium as a diaphragm component. Only a tiny handful, though, use truly acoustic grade, rolled foil beryllium. Instead, most are created via physical vapor deposition (PVD), sputtering a thin film of beryllium onto a conventional polymer diaphragm material like PET within a vacuum environment. This coating technique was first introduced with Pioneer’s famed TAD division back in the late 1970s, when it deposited multiple thin layers of beryllium atop aluminum domes. Our own 17th Anniversary Limited Edition model, DK-4001, DK-3001 PRO, TITAN 6, and upcoming DK-2001 also all utilize speaker diaphragms with beryllium coated via PVD to varying thicknesses.

Beryllium_PVD_Diaphragm_Cropped.png
Computer-rendered diagram of a typical earphone speaker diaphragm
coated with beryllium via PVD. Several of DUNU’s current models use
dynamic drivers that leverage such a technique.​

While this technique remains an economically viable means of delivering a beryllium-like sound quality to the listener, several major challenges are associated with PVD beryllium coatings: durability, limitations to thickness, and non-ideal metal grain structure. These coatings are often brittle, only a few microns in thickness, and possess a relatively coarse grain structure. Rolled foil beryllium overcomes these limitations, and that is why flagship level products in the speaker and full-sized headphone world tend to use this type of beryllium material. It is more durable, thicker, and finer-grained.

The acoustic grade rolled foil beryllium at the heart of LUNA’s 10 milimeter speaker module is sourced from Materion Corporation (née Brush Wellman Electrofusion), the world’s foremost extractor and processor of beryllium metals. Having supplied NASA and the top aerospace conglomerates in the world, as well as major medical device manufacturers, no one has the same amount of experience in refining and processing beryllium. They have a beryllium mine in Utah, a primary processing plant in Ohio, and an advanced processing factory in California. Their TruExtent® speaker domes are used in the highest end hi-fi speaker systems and headphones in the world.

We took the same technology and miniaturized it to the in-ear level .

The major engineering hurdle DUNU had to overcome during the development of the LUNA was the process of getting the rolled foil beryllium diaphragm to be bonded circumferentially to a very thin polyurethane suspension. Doing so required formulating bespoke glues, lightweight and thin enough so as not to impact the total weight of the acoustic system, and reliable enough to be glued evenly against a very thin lip and still confer enough durability to sustain the immense mechanical energy delivered during driver excursion. To harness and control the motion of the beryllium foil, LUNA’s N52 Neodymium magnetic system was custom-ordered with added thickness for much higher magnetic flux across the European-imported CCAW voice coil.

After many design iterations, DUNU was able to meet and exceed our target performance metrics in our computer simulations, and further proved by high-speed vibrometry conducted by a third-party entity. The next step was refining the sound tuning, and this step had to start with the housing material. The base material of the housings for LUNA began as grade 5 titanium alloy. Known for its structural integrity, grade 5 titanium alloy is notable for its prevalent, workhorse-type use in aerospace and other industries where the strength of titanium is its highly important. But we reformulated this alloy with a custom-modified composition to minimize the ringing properties of titanium. Doing so allowed DUNU to bring out the natural, ‘colorless’ timbre of its beryllium driver.

Computer analysis of high-speed vibrometry of LUNA’s pure beryllium foil driver.
The domed beryllium foil is bonded circumferentially to a thin polyurethane suspension,
and thus preserves its pistonic motion almost entirely across the full surface area of the driver.​

As our flagship product, LUNA was tuned to a reference sound signature — deep and natural imaging, even and smooth from top to bottom, and maximized for extension at both ends. The result is the most supremely detailed, transparent, sumptuous sounding earpiece ever crafted by DUNU. It is our best representative of beryllium’s full sonic potential, and we are absolutely thrilled to have everyone experience LUNA.

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Here’s my review of the new flagship from Dunu

The Dunu Luna is an all-new in-ear monitor which features Dunu’s latest driver: a 10mm beryllium foil dynamic driver with a polyurethane suspension that allows for cleaner and more controlled pistonic driver movement. The Luna retails at $1699, putting it at the top of Dunu’s current lineup, well establishing it as their product flagship.

The Dunu Luna was provided to me by Tom of Dunu as part of a loaner tour on Head-Fi. I will be shipping this unit to the next person in-line immediately following this review release.

Driver

I’ve gone over beryllium drivers before, in my recent review of the Focal Utopia, as well as my very own headphones, the ZMF Verite, although that Verite driver is a coated-beryllium driver. In this case, Dunu uses beryllium in a rolled-foil form, making it the first pure Be driver that I am aware of. Others, like the Shozy Form 1.1/1.4 that I’ve also reviewed, are Be-coated drivers over a traditional plastic driver film.

The Dunu driver is only 10mm, which is smaller than their DK-series of hybrids, which feature a 13mm Be-coated driver. With the smaller driver also comes a smaller shell, this time machined from a titanium alloy, which is finished in a silver-matte appearance and flows quite nicely with the Luna name and theme. It’s a very simple, yet modern and sleek design which I really enjoy, and looks right in-line with the other Dunu IEMs.

Fit

The smaller fit does present a small challenge in getting a good fit and deal. Having small ears, I usually don’t mind and favor smaller IEMs, but the Dunu Luna’s small round shape and shallow nozzle length made me always worry about it losing seal or dropping out. Now that said, once I established a good combination of fit and seal, I never really had issues of leaking sound or it falling out of place, but the mental thought of it was always in the back of my mind because it didn’t feel very secure. I ended up with using Size Large Spinfit tips with this earphone, and they are also included in the unit.

Accessories

So along with the Spinfit tips in all sizes, Dunu also includes their own generic style silicone tips, as well as foam ones. The Luna comes with a large carrying case that has plenty of room for extra accessories and a small Digital Audio Player if you so choose. The cable is a light silver, almost white color with mmcx connectors to the Luna, and Dunu’s patented quick connector on the source end. The package comes with all 4 available connectors – 3.5mm, 3.5mm balanced, 2.5mm balanced and 4.4mm balanced. It also comes with a 6.35mm adapter.

Sound Remarks

The Dunu Luna has a general sound signature that is warm, punchy while having a focused energy in the lower treble that some may find brighter than neutral. In total, I find it to have a nice balance of punchy bass and a tasteful upper boost, although it can be occasionally sharp. Let’s talk about it a little more in detail.

When I popped on the Dunu Luna and some tunes, my first impressions where that it was very resolving, with a good amount of detail retrieval, and a surprisingly punchy and warm sound, that I may not have expected just from staring at the graph and focusing on that lower treble peak. Yes, there’s no denying it’s not present, but it’s not nearly as bad as it may look. I also found the Luna to have quick, yet very controlled transient response that I’d expect with a Beryllium driver.

Bass levels are just above neutral, with a bigger focus on mid-bass than sub-bass although it can reach low. There is definitely a punchy attitude to this IEM, although its slam factor isn’t gigantic, it can still provide some when needed. Like I mentioned, bass response on the Luna is very agile, providing good clean and fast response that is good to bring out micro-details from songs. Texturing is good, and overall, I enjoy the bass, though I would prefer more focus on sub-bass than the punchy and warmer nature of the mid-bass boost of the Luna.

In “Cherry-Coloured Funk” by Cocteau Twins, the very opening of the track kicks off with a powerful bassline that is played back with the expected grand nature on Luna. This attribute does lend itself to the mid-bass and warmer style of the IEM, however I did find Liz Fraser’s vocals to be a bit too strained and peaky. Her voice is ethereal already, and headphones and IEMs that exaggerate upper mid-range and lower treble frequencies can make her voice stand out and become overly harsh and fatiguing and the Dunu Luna does hover that fine line.

In Chrvches’ “Get Out”, I found the general sound was very punchy although only had a decent amount of slam. During the bridge, however, I felt the bass and mid-range textures were presented very well on Luna, but again, my main concern is that the chorus, where Lauren Mayberry echoes her “Get Out” song title over and over again, to sound a bit bright and fatiguing.

This isn’t necessarily going to be a problem for every song or style of music, but I do find that the Luna’s 3-6KHz region is over-emphasized and I wish it was tamed down a few decibels so it wasn’t so far removed from the midrange.

This extra presence isn’t always bad though. In the bluegrass pop tracks, “Gravity” and “Restless” from Alison Krauss & Union Station’s early 2000 record, “Lovely Runs Both Ways,” I find that the strings, whether they are guitars, mandolins, dobros or fiddles – they have a nice exacting sound that has nice harmonics that flow and are well conveyed with emphasis. Yes, it can be a little sharp at times, but in general, I don’t find it troublesome at my lower listening volumes. In addition, here, the angelic sound of Krauss’ famous voice is placed in the entire spotlight.

The mid-range has a little bit of warmth to it, which I wasn’t necessarily expecting. It’s not thick by any means, but it has enough body that it doesn’t sound thin. When I listened to some live tracks by the band, Brad, the late Shawn Smith, sounded excellent. His bravado voice carries a lot of the energy I expect. His vibrato-style of singing comes in with good detail and texturing. Stone Gossard’s guitar-work is also clean and precise, and imaging seems to match what I see on-screen well.

In Air’s “All I Need”, vocals sound more forward than other in-ears. The synth melodies the French band produces are very energetic and occasionally shrill, while guitars are well-defined. This song has a lot of textures and layering built-around the keyboards and guitars and I find the Luna plays them back well, however, music like this can be fatiguing over time.

“Rain on Tin” by Sonic Youth, however, sounds excellent. I wish this band were still together, but alas, we still have their wonderful back catalog to choose music from, and like I’ve mentioned before, the Luna’s strengths are its precise string-play, good instrument separation, and (for better or for worse), it’s lower treble harmonics. With Sonic Youth’s abundance and mixture of electric guitars, all on different filters and effects, playing various riffs in full harmony, the Luna does a good job of separating the guitar chaos into a coherent rock song.

Comparisons

The Dunu Luna is a single dynamic flagship IEM and so the comparisons expected are probably to other higher-tier solo dynamics. Unfortunately, I do not have any on hand to demo side-by-side. From memory, I find the Luna to be a cut above the Campfire Vega and Atlas and unfortunately, I have not had the chance to listen to the other new beryllium driver IEM, the Final A8000. While both the Vega and Atlas have much more bass emphasis, I find both to be a bit muddy and lacking clean texture. The Vega is also a bit harsh and sibilant, and extremely fatiguing to me. The Atlas seemed to sound different from the first time I heard it and the following times. That said, I think it’s respectable, but still falls short in the major technical areas that the Luna stands out on.

When comparing to IEMs I do have on hand, I find it’s closest in sound to the Hidition Viento, which I now own both in universal and custom form. While the Viento is a 4-BA IEM, and does not feature a dynamic driver, it does share similarly large pinna gains, though it’s not as boosted in 5KHz as the Luna is. I find the Viento to have a more natural tonality than the Luna and perhaps even image a little better. The Luna is punchier and slightly warmer, and generally presents bass more naturally though both are on the quicker side of things. Viento actually reaches deeper in sub-bass though. In terms of just raw resolution, I think the are both quite close with perhaps a small edge to the Luna, as it mixes both clean raw resolution with a more natural harmonic sound, even if it’s slightly bright. I still prefer the Viento over the Luna though, and that’s based on tonality being more accurate and the better subbass extension.

The qdc Anole VX impresses more in resolution and bass response, while the Luna has a nice well-controlled punch sound that the VX sometimes doesn’t have – punchiness, as opposed to control. That’s something the VX may top Luna in, though again, it’s close. The VX’s bass is weightier and has nice subbass rumble, while also have nice clean texture and resolution, something that the Luna can do too, but without as much weight. I think both have slightly off-skew tonality when it reaches the treble region, with the Luna overly bright around 3-5KHz, and VX having a sharp peak at 7.5KHz which, in both cases, can cause some music to sound a bit plasticky or sharp.

Conclusion

I did not know what to really expect when I got the Luna in. I had not really looked at other reviewer impressions nor had I taken a deep look at the frequency response. I always wondered how a full Be driver could behave in an IEM after experiencing the benefits on the Focal Utopia and Stellia in full-sized headphones. For the most part, I think Dunu succeeded with many of the technical aspects of in-ear audio. I find the Luna has good resolution, transient response, and a nice punchy bass.

Where it does lack is overall timbre and tonality. I wish there was just a little bit more sub-bass boost, and a little tamer lower treble. It’s not as bad as other IEMs I’ve tried in the past, but it can be a little fatiguing at times. When I gave this feedback back to Dunu, they mentioned that dampening the driver to tune down the treble peak would reduce a lot of the technical aspects that the Be driver and limit the potential of the driver.

As it is for most things, it’s a game of compromises. Just like the qdc Anole VX, which excels in technical performance, it does give way to some minor tonality aberrations. The Luna’s trade-off between technical performance and the minor treble peak and inconsistencies is a question for each listener to answer. Besides that, I find the overall package of the Luna to be great with the big complement of accessories, a large well-designed case, and a beautiful cable with quick-connectors for every source.

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That peak reminds me of the RHA CL2, is this targeted or tune more towards the Harman preferred curve?

It does remind me of that, but the RHA CL2 measure with more energy there, and from memory, it’s brighter and what I want to say, incorrect. The Luna is also stretched there but I don’t find it nearly as problematic as what I recall the CL2 was. I measured CL2 on a different rig so I do not have comparable measurements unfortunately.

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Just so everyone is aware, @antdroid’s excellent review of the Dunu Luna has been published on the headphones.com main page here:

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The Dunu Luna is an in-ear monitor (IEM) using a single pure beryllium diaphragm dynamic driver (DD) in each earpiece. The Luna retails for $1700. I had the opportunity to listen to the Luna through a review tour organized by Dunu.

The Luna has an upper-mid forward tuning with an odd presence region emphasis. It is hyper-resolving across its frequency response and boasts effortlessly quick note articulation. In terms of its technical performance, it is competitive with high-end multi-balanced armature IEMS. It benefits greatly from a sub-bass EQ boost.

My extended impressions, along with additional images and measurements, are available on my blog:

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