The Caldera has been reviewed often and in detail since its launch, so consider this my "update" on the Caldera, focusing on the sound of the new Mantle mesh; the sound of various ZMF earpads for this headphone; and a comparison of the Caldera with another open-back planar, the Final D8000.

Background: My first planar headphone (my first serious headphone, period) was the ZMF Ori. The Ori suited my tastes perfectly and introduced me to great planar bass. When open-back headphones became a priority, I assumed it wouldn't be difficult to find an open-back planar as good as the Ori. I was so wrong. Five years and six open-back planars* later, I finally landed the Final D8000 with the D8000 Pro's "G" pads. It's a keeper. Then the Caldera launched (an all-new ZMF planar!) and I had to hear it. My first loaner didn't work out (medical issues), so a couple months ago I purchased a coffee-stain oak Caldera, the subject of this update. Since then this beautiful Caldera has been shaking up my audio world.


Comfort
The comfort of ZMF headphones has become consistently excellent in recent launches, thanks to the redesigned headband. Yes, the Caldera has large wooden earcups with metal screens and hardware. And yes, it's relatively heavy. But thanks to this headband's padding and comfy, spacious earpads, the Caldera is one of the most comfortable headphones I've ever used. I just don't feel the weight of it.

Visual Design
ZMF's earcup screens have steadily become more interesting and aesthetically pleasing to me in recent years. I think the Caldera's screens are the best ZMF ever did, allowing the Caldera to compete favorably with the Meze Empyrean and Elite, which also have large, beautiful screens. I commend ZMF for designing the Caldera screens with a gentle but noticeable concavity (inward slope) at the center. This restrains what would otherwise be a larger exterior radius of these (already large) earcups. It's a subtle touch that visually streamlines the earcups and makes them somewhat easier to handle.

Beyond its screens, the Caldera is the first open-back planar I know of that marries cutting edge planar design with ZMF's classic, heirloom wood craftsmanship. A number of high-end open-back planars are handsome; this one is simply beautiful to look at.

The Caldera Sound
With the sturdy, comfortable stock pads (the best earpads I've ever encountered), the sound of the Caldera is impressive, often surprising and always involving. The Caldera does four things about as well as any other planar (any other headphone, period): resolution; soundstaging; dynamics; and timbral accuracy. I suspect we can thank ZMF's ADS (Atrium Damping System) for the soundstaging, which outdoes every other planar I've heard by a wide margin. And we can probably thank ZMF's CAMS (Caldera Asymmetrical Magnet Structure) for the rest.

• I've heard other TOTL planars with high resolution, a few maybe even more than the Caldera's, but sometimes resolution brings brightness and a lack of musical realism, sounding unnaturally, excessively detailed (at least to my ears). The Caldera's resolution is very high, with impressive "technicalities," but there's little if any sonic toll. There is a dash of warmth here, supported by deep, foundational bass that gives the sound natural weight, pulling it back from the top-lit, edgy tonality that sometimes accompanies high resolution. I hear the Caldera as "ZMF neutral" done right: it facilitates analytical listening (for those who want that), but always lets the music through.
• Soundstaging is not a quality many planars excel at. Dynamics tend to pull ahead here. But the Caldera is different. Its soundstaging is mind-bendingly good. I never once put on this headphone without noticing how well it renders acoustic space. I've heard two other headphones that use the ADS, the Atrium Open & Auteur Classic; the Atrium has the best soundstaging I've ever heard, period, while IMO the AC and Caldera are neck and neck for next best. Most planars don't come anywhere near the Caldera in soundstaging, although some TOTL planars produce a large, diffuse soundstage that is quite pleasing.
• Dynamics often are a strength of planars. I find the Caldera has better macro- and micro-dynamics than any other planar I've heard except possibly the big Abyss. The Caldera has "jump factor" to spare. This brings to mind the ZMF Eikon, one of the most dynamic headphones I've heard. I think the Caldera is even better. With music that gets loud and crazy, I really need a seatbelt and roll bar to use this headphone.
• Timbral accuracy isn't something I noticed much in planars. It didn't seem like one of their strong points. However, I consistently notice excellent timbre in the Caldera; it nails the inherent sound of every instrument and voice, making them sound like they do IRL. That is exceptional performance by a planar driver.

Considering all four of these things, what I hear from the Caldera is an advance in the evolution of planar sound: the deep, pressurized bass, excellent dynamics and high resolution of the best planars, along with soundstaging and timbre that are usually the province of top dynamics.

Hearing Into the Mix
Hearing familiar tunes with the Caldera, I discovered its high resolution and accurate timbre synergized, allowing me to easily "hear into the mix" and distinguish each track's particular tonal values: warmth vs cold, bass-rich vs not, compressed vs not, natural ambience vs EQ'd ambience, etc. I've never heard these sonic cues so clearly before. The Caldera definitely changed how I listen to studio recordings.

Examples: On the superbly engineered "Morph the Cat" by Donald Fagen, the Caldera makes it evident that Fagen constructed a dense, thick, bass-rich sound, anchoring each track from the bottom up, with the concussive title track employing multiple bass instruments of different types to do it. By contrast, 1960s Blue Note jazz dates deliver slight warmth and bell-like midrange clarity, ideal for conveying instrumental tone. And minimally miked & mixed classical recordings put instruments and voices in large, reverberant spaces with little if any sonic manipulation.

With the Caldera, I can appreciate not only the performance and the music, but also the quality of the mix itself. If I was a music studio pro, I'd prize the Caldera for how it reveals the mix without sounding "forensic" or cold.

Tonality
The usual bass/midrange/treble discussion is simple with the Caldera. I hear it as relatively flat from bottom to top with no significant dips or peaks. Because the typical shallow dip in the mids to upper mids isn't present here (at least, not to my ears), the Caldera has a somewhat midrange-forward sound. That's OK because these mids are so expressive and detailed. Note that the Caldera's bass capabilities are so good that with music having strong baselines, it a borderline-bass monster … but only when the music calls for it.

The Caldera's straight-ahead, neutral sound means any peaks in components or music (upper mids or lower treble) come through clearly. That can be problematic for me because I'm more treble-averse than most. That's where the new Mantle mesh comes in:

• My first Caldera (a loaner received late last year) had the original mesh. When there was a lot of energy in the upper mids and lower treble of music, I really heard it. Not a constant thing by any means, but it could become too much of a good thing by interrupting this headphone's otherwise smooth and engaging sound profile.
• My new Caldera shipped with the Mantle mesh installed. I'm not able to directly compare the 2 meshes, but my ears tell me those periodic energy peaks are smoother and less abrupt with the Mantle mesh. Not a huge difference, but a meaningful one for me (I'm more treble-averse than many).

Earpad Rolling
I have four sets of ZMF earpads made for the Caldera. All are perforated. The sonic results of pad swapping were intriguing (and in one case, a revelation) without flat-out ruining the sound, as I've done rolling aftermarket pads on other headphones. The availability of high-quality OEM pads is an real value-add for users inclined to explore different flavors of Caldera sound without resorting to EQ:




Amps & the Caldera
The Caldera is no HE6 or Susvara. Any reasonably powerful amp will get it going. The three solid state amps I tried it on (Violectric V281; Monolith Liquid Gold X; Cavalli Liquid Carbon v2) did very well with the Caldera, as they do with every other planar. The real surprise was my transformer-coupled tube amp, the Icon Audio HP8 (with NOS tubes), which handled the Caldera perfectly and nosed out the V281 for best sound of all four amps.

As with every other planar I've had here, the challenge isn't reaching the desired volume; it's getting the headphone to lift-off, to sound as good as I know it can sound. The Caldera makes this relatively easy. It's not a particularly amp-picky headphone. However, its very high resolution can cause surprises. I heard differences between these four amps more clearly than usual.

The Caldera does scale to a degree with increasing amp power and design sophistication. But it sounds so impressive with all the amps I tried, that I suspect it'll work well with any amp having decent power. This is not a headphones that forces you to 2nd-mortgage the house so you can afford the one unicorn amp it actually sounds good on. For a headphone with such obvious TOTL sound quality, this as a very user-friendly quality.

Caldera vs Final D8000 ("D8K")
For this comparison I used my favorite pads (lambskin thicks) for the Caldera. The Final D8K is Final's former TOTL planar, recently replaced by the D8000 Pro, which is said to have a bit less bass and more energy in the upper mids and treble than the D8000. I replaced the D8K's miserable-feeling stock "F" pads with the Pro's "G" pads, which have perforated alacantra-type material on the face that touches the face. I found the G pads increased both the comfort and sound quality of this headphone. I'm laying all this out because my pad selections may have skewed the results of this comparison to an extent

(Caldera)

• Instrumental separation on Caldera is outstanding. Yet at the same time, the Caldera fully conveys the cohesion of multiple instruments playing together in real time and space. To hear the parts so clearly conveyed as well as the organic whole is something special.
• Caldera bass is a thing of beauty. When you listen to music with little or no deep bass, you'd never suspect how much power this headphone has in the tank. But then cue up a tune with a strong bass part (any bass instrument), and there it is: bass with a heavyweight punch as well as great tonal fidelity, making it easy to distinguish the timbre of upright bass vs electric bass; synth bass vs string bass; etc.
• The Caldera's soundstaging is really bonkers: wide, tall, in front of my head, though my head, sometimes even behind it. There's nothing "stretched" or unreal about the soundstaging. It sounds quite natural, albeit more "present," spatially separate, and distinct than other headphones.
• The Caldera can do "pretty" tone all day long. As great as the dynamics and bass are, this is a headphone that will fully convey the sheer beauty of a string section, a choir, or a solo instrument. When the music is beautiful, the Caldera lets the listener hear the beauty. This is not a characteristic I associate with headphones having as much resolution and clarity as the Caldera, but there it is, easy to hear.
• With stock pads, the Caldera is a powerful, detailed, dynamic headphone that also has real soul. It really swings when the music does. Dynamics with the thick pads are slightly less, but still more than most headphones can manage.

(D8K)

• The D8K requires a little less power than the Caldera. The D8K's perspective is somewhat more distant overall.
• The D8K's soundstaging is in another world from the Caldera's. It pleases me and doesn't sound deficient, but it can't compare with the instrumental separation and spatial clarity of the Caldera. The D8K creates more of a Left/Center/Right soundspace.
• The D8K's dynamics are well above average. This is a very punchy sound. But the Caldera is simply better, with true "jump factor" dynamics. If I'm not expecting this or that loud transient from the Caldera, it might lift me out of the chair.
• D8K's bass is outstanding, absolutely competitive with the Caldera's. D8K's bass sounds a touch "thicker" and weightier (probably due to the "G" pads), though both headphones have killer bass.
• Though I consider the D8K a very resolving headphone, it's not quite equal to the Caldera there.

Both headphones convet music with power and fidelity. Both sound musical, though in somewhat different ways; neither has a cold, forensic sound. Comfort is no contest. My Final D8000 has adequate comfort (better than the stock D8K)—but the Caldera is way ahead on comfort. The D8K's tone is slightly "wetter" than the Caldera, even with the thick pads. I happen to like that, but not everyone does…. The Caldera has a little more treble up top, a little more sparkle. The D8K's treble is shelved down a bit. I prefer that. But pads matter in this context: with the thick pads, the Caldera sounds closer to the D8K.

Both headphones please me to no end. These are TOTL planar designs, and while they look and feel rather different, they arrive at pretty much the same place—excellent, musical sound that pleases me greatly. I need both headphones.

Conclusion
The long wait for ZMF's first purpose-built planar was totally worth it. The Caldera is beautiful; has impressive, musical sound; and more or less laps the field with innovative visual and acoustic design elements. Just my 2 cents, but I believe the Caldera will be seen as the planar headphone design to beat, if it isn't already.

"And now for something completely different"*


INTRODUCTION
In recent years ZMF Headphones launched 6 dynamic driver headphones. The closed-back Eikon and open-back Auteur shared a new biocellulose driver that quickly won praise for incisive neutrality plus the musicality and organic sound ZMF is known for. Now a new ZMF dynamic has arrived: the Atrium. It contains a biocellulose driver plus a new wooden earcup configuration. The Atrium also contains something that actually is "completely different": a new damping system (patent-pending). You can read more about the Atrium and its damping system at ZMF's website:


How does the Atrium sound? Does the new damping system work? Does the Atrium live up to the hype? I'll answer these questions after some necessary housekeeping.


Equipment & Music Used:


The Atrium is a very handsome, heirloom-quality headphone in the ZMF style. IMO the screen is especially beautiful:



So...what's "completely different" about the ZMF Atrium?
After a week of listening to this headphone and putting it through its paces on multiple amps/DACs, mostly with the stock universe pads, I found are two sonic characteristics that are absolutely, undeniably different about this headphone:

A. SPACE (aka "Soundstaging")
The Atrium conveys sonic space in a manner like nothing I've heard before. Most headphones I own, owned, borrowed, or heard at shows convey soundstaging in a way that's familiar to us all. These three elements are always present:

• Left Channel (voices, instruments, notes cluster near or just outside the left ear)
• Right Channel (voices, instruments, notes cluster near or just outside the right ear)
• Center (voices, instruments, notes cluster in between left & right

However, the Atrium renders space very differently from this:

1. The soundstage is larger in all dimensions than I'm used to. Not just on this or that piece of music--always
2. Music occupies the entire soundstage. With the Atrium there's never a shrinking soundstage on this or that cut
3. And the placement of instruments, voices, musical notes and sounds within the Atrium's soundstage is far more exact and three dimensional than I've ever heard

These novel qualities occur all the time, regardless of amp, DAC, and music genre. I've encountered this same tangibility & exactitude of space in the soundstages of large, expensive speakers, the kind that cost more than a good used car. But on headphones? Not until the Atrium. The word "immersive" gets thrown around a lot. Well, "immersive" absolutely describes what the Atrium does with the spatial information of recordings.

I envision the soundstage of the Atrium as a wide column on its side (passing through my head, side-to-side) with each end being gently rounded. The column extends 3-4" beyond each side of my head and a few inches out in front/back/all around my head. Inside this soundstage column, sounds & musical notes are anchored with unmoving solidity. There's nothing vague, suggested or virtual about the Atrium's soundstage.

For example, one of my favorite funk music cuts soundstages on the Atrium as follows:


Beyond the Atrium's three dimensional spatial solidity, musical notes themselves were more tangible and dimensional than I've ever heard with a solid state amp. Each note firmly occupies its allotted space in the soundstage.

For me, headphone soundstaging manifests most clearly with classical music, which is routinely recorded with minimal miking in a natural, acoustic space. Classical music typically reveals the full width and depth of a headphone's soundstage in a way that electrically amplified music or purely electronic music cannot.

But it was the reverse with the Atrium. Its soundstaging and spatial qualities are most evident on amplified blues, funk, or rock; and even better, on thick, murky, swirling electronic music. It's child's play to hear into these tracks and unpack how they were mixed; processing applied to certain instruments; reverb & other effects used.

This cut below is one I keep coming back to. It has a thick, processed, boosted/"pushed" sound--which the Atrium dissects like that frog in 9th grade biology. I can hear absolutely EVERYTHING in the mix; every note shimmers in its own space. That just doesn't happen with other headphones:




This brings me to the second startlingly different quality of the Atrium:

B. CLARITY (aka "Resolution")
The Atrium has easily the clearest, most defined sound of any headphone in my experience. I would guess a lot of the Atrium's clarity derives from its three dimensional soundstage and depiction of space. But this clarity is more than just a manifestation of space.

Over and over with the Atrium, a strange thing happened: I'd be listening to some piece of music I know by heart —and suddenly I hear a thing I've never heard before (a hand clap, foot stomp, spoken word, anything). Sometimes it was something I had heard before, but quite faintly, subliminally—and now with the Atrium, I hear it overtly and clearly in a way I hadn't before.

It's audio myth (and cliché) that "the sonic window suddenly loses its haze and becomes crystal clear, so that all is revealed as never before." But with the Atrium it's not myth or cliché. It happens every day on random pieces of music. After a week of this I got used to it, but at first it's downright spooky to hear utterly new things in familiar music.

Example: listening to the well-recorded 1st album by trumpeter Blue Mitchell (1963/Blue Note/Van Gelder Studios), the instruments appear suddenly--I mean right there, precisely fixed in space. It's as if a miniature trumpet is being played 2"-3" in front & to the right of my right eye (this is on a solid state amp, not a tube amp that adds 3D space and layering). I could easily hear how hard Mitchell blew the trumpet to play soft passages. As each note came out of the bell of the horn, I heard how silky smooth it sounded and how it softly rang the brass of the instrument. I know this recording by heart but never heard such resolution before the Atrium.

This kind of hyper-resolution happened again and again on many different instruments, voices, and genres.

I found the Atrium to sound planar-like in the speed with which notes appeared, then disappeared against a black background. With planar drivers that effect results from a combination of:

• low distortion, planar drivers being directly driven and thus well-controlled and less prone to ringing
• and the discrete/precise manner by which planar notes are launched magnetically

I'd guess the Atrium's planar-like sound results from its new damping system and perhaps also from the angled positioning of the driver to fire at the ear rather than directly into it.


Net Result: The Atrium's highly evolved spatial characteristics and clarity make this the most "forensic" headphone I've yet heard. IMO music professionals would kill to have a headphone that so easily allows them to distinguish every element in their mix. The Atrium lets you dissect any piece of music like that frog in 9th grade biology.


Definitely not. This is one of the very few headphones that lets you have it all: high resolution, all the "plankton" you could want, and an unforced, natural sound that puts music first.


Now let's go over the traditional bass/midrange/treble dinstinctions often employed in the evaluation of headphones:

Bass: With stock pads the bass can be epic and impressive. Bass lines suddenly appear with such speed, impact and distinctness that I jumped in my chair a few times. It's a very Atrium thing to hear bass parts swell up from underneath and suddenly be right there, anchoring the entire soundstage and other instruments.

The Atrium has sub-bass for days: if there's any sub-bass in the recording, you'll hear it all. Besides excellent bass depth and impact, the Atrium also resolves the timbre & tone of bass instuments as well as, if not better than, any headphone I've heard. It's easy to distinguish bass notes from a upright string bass vs electric bass or synth. I could also rather easily hear subtle differences between various electric basses. IMO the Atrium with stock pads is a must-audition for bassheads.


Midrange: This is where most of the music lives, and it's where the real magic of the Atrium happens. The Atrium's midrange is a large, spacious place. Most of my listening focused on the mids. That's not because the Atrium is midrange-centric. It isn't. In fact, with stock pads, the Atrium is an unusually neutral and balanced-sounding headphone. But the mids are where the Atrium's unique soundstaging and clarity come through most clearly.

Treble: My hearing probably doesn't go as high up as many here. But I detect no roll-off or "ceiling" in the treble of this headphone. In classical violin concerti where the violin ascends to the very top of its range, I heard every note clear as a bell. And speaking of bells, on carillon tunes (music for brass bells & chimes), I hear the full "shimmer" of the higher notes' harmonics. This is excellent treble, unaccented and unexaggerated.


AMPLIFIER MATCHING
The Atrium is not amp-picky in the least. I got terrific sound out of all 4 amplifiers used. Due to this headphone's exceptional clarity, be prepared to hear more deeply into your upstream gear than usual. That's a plus in my book.

"VOICING" OF THE ATRIUM
This headphone definitely has the ZMF "house sound." It reveals the timbre of voices and instruments—not just the accuracy of reproduction, but their musical quality (the beauty). Via the Atrium music flows in a most natural, organic way, as it does with other ZMF headphones I own or owned. With stock pads especially, IMO the voicing of the Atrium is impeccable, near-ideal.

But if you feel like deviate from the Atrium's stock sound, just try either of the other pad options I heard:



Earpad conclusion: I believe ZMF chose the stock pads for good reasons. To my ears they are the most revealing of the Atrium's remarkable clarity, resolution and soundstage, while also conveying the musical, ear-friendly ZMF "house sound."


COMPARISONS
I spent most of the time listening to the Atrium. But there are two other excellent headphones that IMO it should be compared to:

1 – Final D8000 (with the Pro's "G" earpads)
This very fine open-back planar is the most sonically similar to the Atrium, at least in terms of frequency voicing. And since the Atrium has distinct planar-like sound in certain respects, this strikes me as a natural choice for comparison. I hear some very interesting things when comparing these headphones:

• The Atrium's soundstaging is qualitatively better than the D8K's, but not by much. The exceptionally anchored and dimensional nature of the Atrium's soundstage takes the day here. Which doesn't change the fact that the D8K has the best soundstage I've ever heard from a planar, and among the best I've heard, period
• The very high resolution of the D8K slightly pulls ahead of the Atrium. Not a surprise, really: this planar has just about the best resolution I've ever heard, other than the next headphone listed here
• Comfort-wise the Atrium trounces the D8K. Again, no surprise. Comfort with the D8K is acceptable, but not nearly as evolved with the Atrium
• Both headphones combine high resolution with a slightly warm, natural musicality (Atrium w/stock pads). This one's a toss-up

The only real surprise here is the bass. As planar-like as the Atrium is, and as good as its bass is, the D8K wins by a nose due to the heavy/weighty feel of its bass notes. Planar bass usually beats dynamic bass, at least for me, and that's the case here. Still, the Atrium comes very close, indeed…


2 – ZMF Verite Open (silkwood + stock earpads)

The VO is my current favorite headphone, and it, too, is relatively similar to the Atrium in terms of frequency voicing. This is what I hear:

• The Atrium's soundstaging is better than the VO's, but again, not by much. The VO's soundstage is a bit less wide to begin with, and it can't match the solidity & anchoring of notes/voices/instruments that the Atrium routinely does. The Atrium pulls ahead with music that has a strong bassline and beat, though the VO's natural staging of classical music is very pleasing
• The Atrium's bass is better, deeper and harder hitting. But the quality of the VO's bass is exceptional, particularly how it conveys tone & timbre of bass notes/instruments
• The VO takes the prize for overall tonal purity. I continue to be impressed by the musical, flowing, organic tone of the VO. More than any other headphone I know, the VO fully communicates the sheer beauty of music. Its sound on classical music is particularly ravishing

Desiderata

• Comfort: With my aged cherry/black hardware Atrium, I found its comfort to be the best I've ever experienced with a ZMF headphone (I have 3 and have zero complaints about any of them). It feels light; the clamp pressure is ideal; and the newly contoured headband works like magic.
• Complaints/issues: There's just one and it's minor. I find it too easy to remove the ear pads just by brushing against them. Even a slight sideways tug will completely remove the earpad. The reason is that the groove behind the baseplate (where each pad's backflap inserts) seems shallower than I've seen on other headphones. Usually it's 3/16-1/4" or so deep; here it seems to be in the 1/8" range. That's a small difference, but it means the pads are held to the earcup less securely. Note that this issue doesn't matter at all when the headphones are on my head--only when I'm handling them.

IN CLOSING
I think the Atrium is an extremely good headphone: handsomely constructed, well-designed, and very good sounding. I also think it represents a paradigm shift in headphone soundstaging and clarity, courtesy of driver positioning and the innovative new damping system. If the sound of the Atrium is any test, that damping system succeeds completely and will hopefully appear in future ZMF headphone designs.

Regarding the rating: the Atrium is very very good, but it's not perfect. So giving it a 5.0 out of 5.0 seems excessive. I chose a rating of 4.5 as the most accurate/reasonable alternative.

Over the past year or so, I heard 3 iterations of extensive HD650 mods from Jupiter Audio Research (the "JAR-650," aka "J-Mod"). A month ago I received the finalized J-Mod that is the subject of this review, plus a stock HD650 for comparison.

I'm late getting to the Sennheiser HD650 party. It's easy to see why so many love this headphone. Had I not heard the J-Mod, I could happily live with the stock headphone. It's voiced perfectly for my tastes and scales up readily with better sources. And as my review of the J-Mod will show, it has considerable potential for even better sonics.

Regarding mods: Modding HD650s is a major indoor sport in the headphone community. I'm not very familiar with any of those mods: I haven't heard any, also haven't done any myself. I do know certain elements of known HD650 mods are used in the J-Mod—ie, removing the inside foam layer covering the driver; removing the dome covering the driver's outside center. Nevertheless, the J-Mod is more extensive and ambitious than any discreet mods I've heard of:

• The stock grill is replaced with a proprietary, 3D-printed, custom-damped, dimensional screen

• Internal damping is added and some stock materials selectively removed from each earcup

• Each physical element of the J-Mod has been rigorously/repeatedly auditioned & adjusted for best sound (over a period of several years)

The J-Mod represents a true evolution of the HD650--a complete re-imagining & re-voicing of the stock headphone.

Disclosure: I paid market rate for my J-Mod & have no business relationship w/Jupiter Audio Research or this mod.



SUMMARY/CONCLUSION
I'll get right to the point: the J-Mod sounds amazing. I was unprepared for how compelling the J-Mod is. My usual J-Mod experience went like this: put them on, get lost in the sound--then have trouble taking them off.

The J-Mod changes the stock headphone's sound for the better in multiple ways, all positive (details below). I can't hear any downside to the J-Mod. The stock HD650 already has impressive sonics, and the J-Mod takes it across the finish line into near-endgame territory (surely as close as one could hope at this price). I definitely prefer the J-Mod over stock.

The J-Mod is strongly recommended. Choosing the J-Mod over stock is a true no-brainer IMHO.

Figure 1: J-Mod




Figure 2: Stock (left) vs J-Mod (right) – inside view


Figure 3: Stock (left) vs J-Mod (right) – outside view




Figure 4: Stock (front) vs J-Mod (back) – Side View




THE DETAILS
As many of you already know, the stock HD650 is a somewhat bassy, warm, yet relatively articulate & resolving design. There's little or no sub-bass. The midbass has a "hump" and bleeds into the mids somewhat. The midrange is the star here, carrying most of the information (in a musical fashion). Then comes the well-known "Sennheiser veil" in the upper mids/lower treble, and to my ears, a drop-off in the treble (which sounds pleasing, but really isn't the main action).

What does the J-Mod do differently vs stock?

1 – Better damping: The single biggest difference I hear between the J-Mod and stock is the near-complete elimination of reverberation, note-blurring, and other time domain sonic anomalies. As pleasing as the stock headphone sounds overall, after hearing the J-Mod I realized stock is somewhat under-damped and reverberant.

2 – Resolution & clarity: Considerably better in the J-Mod, in part because of better damping. Notes stop and start quickly & with authority, almost as planar drivers do. On the J-Mod I can more easily/clearly hear subtle spatial/ambience cues, reverb "tails" & sounds buried in the mix. I wouldn't hesitate to recommend the J-Mod for studio monitoring (not something I'd recommend for stock).

3 – Dynamics/"jump factor": With reverberation under control in the J-Mod, dynamics take a leap forward. This is lively, exciting headphone audio, far more so than stock. The J-Mod really nails dense/multi-tracked music such as well-recorded studio rock/pop, hip-hop, reggae, Afropop, Latin jazz, R&B. And with those old sonic standbys for the stock headphone, acoustic music and classical, improved dynamics produce a seemingly uncompressed, life-like representation of the original venue.

• I have some smokin' hot Latin jazz tracks w/brisk tempi, dense rhythms & multiple/layered percussion parts. Those tracks are killer on the J-Mod: instruments seem to pop out of nowhere, and percussion surrounds my head in a precise, well-spaced array (see "Soundstaging" below). Sometimes it's hard to sit still when listening the J-Mod, not something I can say about stock.

4 – Soundstaging: The strong basic capability of the HD650 driver is the key here. Both stock & J-Mod have soundstaging of the "intimate/defined" variety (vs huge & spacious). But with the J-Mod's flatter, less reverberant sound, soundstaging is even more precise & exact (ie, this instrument is right there & that one is right here). The soundstage is close to my head, but it's so precise that, especially with multi-track recordings, there's quite a lot of side-to-side soundstage movement. IMO soundstaging is a strength of the stock HD650, and the J-Mod makes it even better.

5 – Tonality: The stock HD650 sounds to me like a gentle, upside down "U"-shaped curve, with falloff at either end and slight elevations in the midbass & midrange. By contrast, the J-Mod sounds level: the mids are excellent, yet there's more/better performance in the bass and treble. Thus the J-Mod sounds flatter, more precise & controlled--yet not hyped or tiring. Instrumental and vocal timbre really comes through on the J-Mod--again, aided by its reduction in resonance and resultant colorations.


All these positive changes work together to make the J-Mod a very compelling headphone. As much as any headphone I've heard (at any price), it sounds like real music.


OTHER OBSERVATIONS

• Burn-in: The J-Mod definitely benefits from burn-in. I burned it in for ~80 hours, and during that time, the bass and lower midrange deepened and became more present—a perfect match for the incisive, high-flying treble. The resulting tonal balance is just about perfect IMO.

• Amping: I listened to the J-Mod on 4 solid state amps (V281; LC v2; Lake People G109-A; M Stage Matrix HPA-1); and an OTL tube amp, the Woo WA3. The surprise was that I preferred solid state amps by a large margin. Not sure why, but the J-Mod is amp-agnostic and can sound very good with less-than stellar sources (it sounded fantastic on the HPA-1, my cheapest & least powerful amp). I heard the expected differences between these familiar SS amps, but those differences were not spotlighted by the J-Mod. Balanced cable & amp sounded better than SE, but again, margins were not large.

COMPARISONS
How does the J-Mod measure up to other open-backs? I wasn't able to compare it to high-end flagships like the HD800, Focal Utopia, ZMF Auteur, or Stax SR009. Those comparisons would be fascinating; the J-Mod may well give these far more expensive TOTL designs a run for their money.

The J-Mod is clearly on a higher level than another open-back dynamic, the slightly less expensive Fidelio X2, which is lots of fun, but less resolving & with more diffuse/imprecise soundstaging than the J-Mod. I also find the J-Mod sounds better in every way than the Onkyo 800A (comparably priced).

At or just below the $1K price-point, though, things get very interesting:

• I heard the Hifiman Sundara and Beyerdynamic Amiron Home at CanJam (both ~twice the price of the J-Mod). I believe the J-Mod handily outperforms both

• I also heard the MrSpeakers Aeon Flow Open (a planar that's ~2X the cost of the J-Mod), and believe it's nose-to-nose sonically with the J-Mod (differences being relatively minor)

• A headphone that begs comparison with the J-Mod, based on similar voicing, is my LCD-2.1, a pre-fazor open-back planar with terrific sound. The two headphones compare quite well in overall tonality, soundstaging, and resolution. The LCD-2.1 has the sub-bass both the stock HD650 & J-Mod lack, and is just a bit better in other ways. Still, differences are rather small; the J-Mod matches very well with this legendary Audeze design

So the J-Mod is comparable to (or better) than headphones costing up to 3X its price. The J-Mod impresses me as a sonic over-achiever that pushes the limits of mid-fi, even getting into high-end sound.


Pricing/Contact Info
J-Mod is the brainchild of Jupiter Lee at Jupiter Audio Research (@ext1 on Head-Fi). Please contact him for quotations and additional information.

The price of a new J-Mod/HD650 is $390 USD (not incl. shipping). Jupiter will mod currently owned HD650s for $100 (not incl. shipping) upon request.

Takeaway: At these prices, there's no good reason to choose the stock HD650 over the J-Mod. Sonically, the J-Mod is a must-have headphone.

Background: I've been impressed by the inexpensive Marantz MPH-2 ($39.99)—especially its bassy, non-fatiguing sound. The MPH-2 is one of 5-6 "clones" (re-licenses) of the original ISK MDH9000 design. I've owned 3 pairs of them (kept one MPH-2, gave the other plus a LyxPro HAS-30 as gifts). As long as they use the same quality pleather earpads found on the Marantz & LyxPro, the clones sound identical. Recently I became impressed by the intricate, imaginative mods posted on Head-Fi by @Slater. He also likes the MDH9000 clones—so I asked if he'd do a top-to-bottom mod of a new one.

His mods included:


This review compares his modded Akai Professional 50X headphone to my stock Marantz MPH-2. I listened to the mod for weeks on a range of music (studio pop, blues, R&B, funk, rock, jazz, Afropop, reggae, a bit of classical). To identify mod vs stock differences, I switched these headphones repeatedly (same cable, amp, volume) to compare their sound on the same music cuts.


CONCLUSION:
(didn't think I'd make you wait for it, did you?)
The modded headphones are significantly improved in nearly every way vs stock. It's one of the most fun headphones I've heard (my feet tap whenever I hear it). It's an understatement to say @Slater's mods were successful: these mods showed me just how good this driver & enclosure can sound (details below…)




Frequency range/sonic profile:
The greatest change in the mod vs stock is here, something I least expected. The basic sonic profile of the stock headphone is retained in the mod, but with many changes:






Resolution: Compared to stock, it's as if 2-3 layers of cotton have been removed. The clarity and resolution of the mod are far beyond what the stock headphone can do. IMO this is the most surprising benefit of the mods. I hear "into the music" on the mod in ways I can't on stock.

Dynamics: The stock headphone has a pleasing sound but isn't particularly dynamic, with soft/loud differences not very good unless the volume is cranked. The mod improves on this, with dynamics that range from above average to excellent, depending on the source. Improved dynamics combined with greater resolution make the mod compelling and exciting to listen to.

Soundstage: The stock headphone's better-than-average soundstaging is one of its best qualities. Still, the mod is better, as expected with open-back conversion. The headspace is larger; notes are a bit further from my head all around, and sound placement in space is distinct. The channel separation is also improved (didn't expect that). The net effect is that notes surround my head; on the mod, percussion in particular sounds very distinct & well-anchored in sonic space.

• One advantage of the open mod is a more relaxed feeling when it's on my head…less of that "pressurized" feeling I get w/stock. As a result, I can listen longer.
• Despite being open-back, the mod is still relatively isolating, perhaps because the grill/opening is <1/2 of the total outside surface of the earcup. However, anyone needing complete silence in a shared workspace may have issues with the mod (not the stock headphone--it's dead quiet).

COMMENTS
Clearly I like @Slater's modded Akai. But I also want to understand where it fits in the headphone landscape. Did the mods make the Akai the equal of the Sennheiser HD800 or Focal Utopia? Of course not. Even fully modded, this headphone is middle-of-the-road audio, falling short of the finesse & refinement of TOTL designs. In the more affordable realm, I've heard 3 headphones whose sound is roughly comparable to the mod.

In other words, these mods pushed the sonic value of the Akai to ~5X–15X its retail cost. That's just one person's opinion—but still, it's quite an achievement for the mod to match up with costlier headphones.

Finally, there is even some user-customization available in the mod (Figure 8). One simply removes the earpads and covers more or fewer of the 18 exposed holes that ring the driver (9 holes on each side). The mod came to me with a total of 8 of the 19 holes covered (4 covered on each side). @Slater explained that I could increase bass (and simultaneously drop midrange level) by uncovering holes; or do the reverse by covering more holes. I played with this enough to know that I couldn't really improve on his tuning.

INTRODUCTION: A couple months ago I happened to see these headphones on Amazon.co.uk. There were many more reviews on Amazon.co.uk than Amazon US: most were very positive, with few coming from product give-away. I also viewed 3-4 YouTube videos about these 'phones. The common theme seemed to be young listeners using them at work, with mobile devices, or in some cases in home studies, and being rather shocked at how good they sounded. Most reviewers weren't sophisticated audio types or headphone fanciers, yet many spoke about sound quality, as if surprised to find themselves doing so. That interested me, so I ordered them from ebay; total cost, incl. shipping - $78.58.
 
Appearance:
I thought they'd look garish (that candy-color cord certainly does)--but they actually look understated and, beyond the chrome outside of each earcup, rather handsome. The 1st pair had a dead left channel, so after 3 weeks waiting (return/credit/reorder, this time from Amazon for just $59.99), the 2nd pair arrived. I'd never actually heard them, so after attaching am aftermarket cords (because that stock red cord looks like a Twizzler), I plugged them into my Matrix M Stage HPA-1. Would they work? Would they sound ½-way decent?

 

Yes...oh, yes! In fact, on that 1st day I had trouble taking the Yenona's off my head. They were shockingly good. That's with zero warmup, straight out of the box. I was really unprepared for how good they sounded.

 

Several weeks later, after ~125 hours of warmup, I had listened to them with a range of music (classical, pop/rock, R&B, blues, reggae, world music, jazz, American songbook singers) on 3 different amps:

 

-- DAC/amp, FiiO 10K

-- Matrix M-Stage HPA-1 (fed by Audio GD NOS 19)

-- Lake People G109A (fed by Audio GD NOS 19)

 
Usability:

Unique among headphones I've seen, these not only have a detachable cable, but one earcup has a 3.5mm jack and the other a 6.5mm jack. That silly-looking red cable addresses this design: one end has a 3.5mm jack, and the other a 6.5mm jack. This gives considerable flexibility for mobile vs home listening.

 

I never tested that cable & in fact, quickly ran into issues with the 3.5mm jack while using my excellent Ghent Audio 2M, 3.5mm to 6.5mm cable: the Yenona's 3.5mm jack is rather  loose--my cable fell out repeatedly. Finally I gave up and plugged the cable's 6.5mm jack into the Yenona's 6.5mm input on the other earcup. That is solid & secure.

 

Still, the low price of this product has to be evident somewhere, and input jacks seem to be the place. I would hesitate to repeatedly plug & unplug cables with these headphones on daily basis, tempting though it may be.

 

These headphones are rated at 32 ohms and were easy to drive with any headphone amps on hand (I didn't test them with a mobile phone or other miniature device).

 

The final picture above shows the 6.5mm end of my Ghent Audio cable plugged into the Yenona's,

 

Comfort:

Once adjusted for my rather large head & ears, these headphones were extremely comfortable. I haven't weighed them, but I'd guess they're in the 250-300 gram range, considerably less than the  Fidelio X2's. The pads are soft (though not squishy) & quite deep; my ears don't touch the drivers. Clamping pressure is low and the padding inside the headband is more than sufficient. After awhile, I simply forgot they were on my head. My ears do get warm during extended listening, as the seal is good and the pleather pads don't breathe much. Also, the soft foam of the earpads may eventually become a problem, though it hasn't been yet. I'll try replacing the pads w/extra thick Brainwavz HM5s (which may be slightly large for these 3.9" diameter headphones). But that's hardly a necessity…right now, it's all good. Overall, these are relatively light, manageably sized headphones.

 

Tonality:

The Yenona's have a warm sound, more of a welcome flavor than an overpowering coloration. Also, it changed as I moved from amp to amp, with more warmth on the FiiO, most of all on the HPA-1, and least on the Lake People.

 

The bass is good. VERY good. I'm not sure how much sub-bass there is (the Fostex TH-X00's definitely had more)--but the bass range is all there, strong in quality & quantity. If you want accurate reproduction of string or electric bass, the Yenona's will give you all of it. They'll also reproduce high-impact bass waves from well-recorded studio music with large bass transients: such the title cut of Donald Fagen's MORPH THE CAT, where the opening note is a huge pulse w/Freddie Washington's Bass, Fagen's Fender Rhodes, and no doubt over-dubs of each + 1-2 uncredited synths. At high volume, this cut is a real speaker killer. The Yenona's transmitted that full pressure wave…I really felt the bass (not all headphones can do this).

 

Interestingly, th bass didn't seem to bleed into the midrange or affect the balance of these headphones. I listened to much classical music on the Yenona's—a cruel & revealing test for typical  U-shaped, "fun" headphones—and was surprised how consistently good they sounded with this very different music. Every instrument in the orchestra sounds like it should. Again, not all headphones can pass this test. 

 

However, the Yenona's bass can become boomy & overblown when the amp itself is warm & bassy. This happened occasionally with the M Stage HPA-1 on certain recordings.

 

Treble is very nice: there's a little bite when it's present in the recording, and otherwise a nice sparkly  sheen. Just about perfect. Definitely not fatiguing or hyped, nor does it sound shelved or recessed. Particularly on the Lake People amp—the most "honest" of my HP amps—I could clearly hear more upper midrange & treble energy in some recordings, yet it never became bright & sibilant. The Yenona's have a graceful, non-aggressive way of signaling brightness in recordings…a neat trick.

 

Resolution:

To my surprise, these headphones have real resolution, far more than I expected from these inexpensive closed headphones. I could listen deeply into familiar recordings; details had subtlety & texture (this was  a big surprise).

 

Again, it was classical music that revealed resolution, as I could distinguish subtle instrumental timbres, the difference between singers, small sounds in the orchestra, etc. Also, in closely miked studio recordings of singers, intimate breath sounds, lips touching the microphone, etc. could be readily heard.

 

These aren't top-shelf Sennheisers or Grados. Still, the Yenona's seem to have more resolution than other headphones I've heard, including the Philips Fidelio X2's and Fostex TH-X00's.

 

Soundstaging:

Another pleasant surprise: the Yenona's have real soundstaging, admittedly not as much as open headphones, but more than other closed headphones I've heard, including the Fostex TH-X00's. There's real depth and space here. This was especially clear in classical recordings and naturally miked studio jazz recordings.

 

CONCLUSION: After all the analytical listening was done, I find myself grabbing the Yenona's every time I feel like using headphones. They're so light, comfortable, and easy on the ears that they've displaced the Fidelio X2's as my go-to 'phones. I've forgotten all about their low price and how they shouldn't be/couldn't be this good…I just put them on and listen. STRONGLY RECOMMENDED.

 

 

Footnotes:

1. If you search for the Yenona's, you may see a white-stitched variant lacking the red design highlights and shipping with a black cable, not red. For those in the U.S., be advised it's difficult if not impossible to purchase this variant (I tried). The pair you get in the U.S. is the red design.

2. I like the earpads of the Yenona's well enough to email the manufacturer and ask if I can purchase a couple extra pairs. For those who buy aftermarket earpads, you know the rarity of good-quality round pads (all the terrific Brainwavz being oval; and the Beyer rounds being velour, not usually desirable when replacing pleather originals).