Hi guys,

would like to share some impressions with those who are on the fence of buying these - may or may not be of help to you!

My PMx2 are rev2 version but customized with velour pads from the original rev1 version. Alex also tuned my headphones to be as neutral as possible (according to his reference pair) which means treble may not be as forward as some of the rev2 pairs out there (but still should be a bit more present and airy compared to a typical rev1 pair). Graph provided by Alex is enclosed. Audio chain I have been using lately consists primarily of Schiit Modi Multibit and Audio-GD SA31-SE, with digital side of things being supported by Jriver MC software and toslink cable for digital transmission from my computer. I would say that the chain complements planar magnetic headphones very well.



Impressions in bullet points:

• Tonality and timbre: A dream come true for me = a hybrid of HE500 and LCD2 rev2. Very mature and speaker-like presentation. Excellent tonal balance from bass to low treble (e.g. HE500 with the original transparent-plastic-ring velour pads) combined with bass, smoothness and intimacy (e.g. LCD2 rev2). Deep thunderous bass, clean and organic mids, smooth but present treble. As expected, timbre is also perceived as somewhere in between those two planar magnetic cans. Every music track I throw at them sounds natural, from EDM to extreme metal. Beware - it is very easy to shift tonal balance of PMx2 rev2 to warmer or brighter side as you move from one audio chain to another (or as you just keep swapping particular components).
• Technicalities: Reminds me of HE6 to some extent - clean and tactile performance. Very smooth presentation from bass to treble that is fortunately not holding these cans back due to accurate transient response. There is no muddiness or unnatural sharpness to their sound, they just sound 'fast' in the right way to my ears. Perceived clarity and airiness of PMx2 rev2 depends considerably on upstream components - satisfactory for me but those in love with extreme openness and airiness of HD800/HE6/Stax may have complaints. PMx2 rev2 seems detailed enough for me next to HD800/HE6 duo to call them 'high-end' but neither my upstream gear nor my music library are 'high-end' enough to reliably confirm this feeling of mine.
• Soundstage: Average in a good sense - does not really lack or overblow dimensionality, width, depth or imaging but of course cannot match enjoyment given by HD800, K1000, MA900 or similar. Stax and HE6 also have advantage here. All in all for sure better developed than Audeze LCD2 rev2 but even HE500 can be a tiny little bit ahead for some due to brighter treble response and more open nature. (PMx2 are rather semi-open than fully open.)
• Ergonomics: Form-factor is almost perfect - transportable but still fully circumaural (unless you have very large ears), a bit heavier due to beefy magnets but still very comfortable to wear thanks to excellent headband and velour earpads. Only complaint here is zero resistance of 'gimbals' holding and enabling cups to rotate. It subjectively makes the phones feel a bit flimsy (even though they actually are not) when you are putting them on/off your desk. Combination of 1-meter long 3.5mm cable with 3-meter long 4-pin XLR male cable is just perfect for me. Provided transport case is just ideal to keep going around with PMx2s.

I will probably get rid of HE6 and maybe even HE500s (HD800 already gone), both beloved cans for the past few years. PMx2 rev2 just seem to be the one headphone I was chasing for a very long time. The neutral one.

Are they worth the current asking price (1899USD)? This is a question only you can answer for yourself. To me, they are very well worth the price. Compared to what is currently on the market, I actually consider them a bargain.

DISCLAIMER: PMx2 rev2 are not perfect, nothing is. But I am having a very hard time pointing out any issues. They just tick all the boxes for me since I happen to value neutral and clean presentation lately over 'brutal' technicalities (soundstage, microdetails, sharpness, ...).

The Standard Intro (stuff you can skip)
 
Disclaimers I borrowed the set of PMx2s used in this review from Alex at Audio Zenith.  Thanks Alex!  Other than that I have no relationship with Audio Zenith or with the maker of any other equipment I used in completing this review.
 
About me I usually listen at low to moderate volumes (about 57 dB casual listening, maybe 67 dB rocking out).  Preferred music genres are 70s rock & progressive, electronica, dubstep, female vocals.  My current primary systems are Yggdrasil\Ragnarok stack and a QuestyleCAS192\DNA Stratus.  Most frequently listened to headphones recently are Senn HD800s (which have never had a treble issue for me) and HiFiMan HE-X.   I also own the OPPO PM1, PM2, and PM3 headphones.
For this review I used the Questyle DAC feeding the Ragnarok via no-name balanced cables through goldpoint switches.  Software is JRiver 21 with no plug-ins.
 
The Actual Review (stuff to read) (or just skip to the conclusions below)
 
About the PMx2
 
The Audio Zenith PMx2 is a heavily modified version of the OPPO PM2, tuned to the standards of Alex Zaets at Audio Zenith.   Alex is a measurements guy and saw a lot of un-tapped performance potential in the OPPO PM1 cans.  When OPPO released the PM2 with essentially the same hardware as the PM1 but at a much lower price point, he saw the opportunity to apply his preferred engineering and sound tweaks to enhance these cans. The result is a definite improvement in sound but at almost double the price of the underlying hardware. Youch! Is it worth it?  What does that $$ get you?  Read on to find out, or jump your ADD self to the conclusion.
 
 

 
Build Quality and Design
 
The PMx2 have the same body and chassis as the OPPO PM2 (or PM1 if you want to have Alex mod those instead).  I consider cans these a hybrid of open and closed back designs.  It’s not an isolating headphone, I can generally hear what’s going on around me.  It leaks less sound at lower levels (duh), but it doesn’t leak terribly at higher volumes.
 
The underlying OPPO chassis quality and finish is first class and in line with flagship headphones.  No loose parts, no rough edges, well thought out hinges and headband.  Opinions may vary on the looks but the phone is well put together.
 
When you get these from Alex the quality remains but the Audio Zenith mods change several aspects of the design.  About 80 grams of weight have been added, putting more pressure on the padded head band.  Padding on the headband appears unchanged from the stock PM2 & is still enough to handle the extra weight.
 
The ear pads (removable on the PM-2) are permanently fixed on the PMx2.  Besides preventing you from swapping out pads this also prevents access to the drivers.  Any future repairs would probably have to go back to Audio Zenith so they could re-pad it afterwards.  The PMx2 ear pads appear to be built with stock PM-1 velour coverings, re-stuffed with multiple zones of memory foam. Per Audio Zenith they were engineered to help with the PMx2 sound signature.  After listening to them I definitely buy that.
 
Audio Zenith has re-badged the stock OPPO chassis with decals, which I think slightly detract from the overall finish.  These are custom cut for the purpose and extend to the carrying case which has also been rebranded.  This is an understandable decision as OPPO used most of the flat surfaces on the cans for branding, and re-engineering those parts would add both cost and complexity to the mod.  I’m not a fan of the stick-on look however and worry about the durability of the multiple badges.
 
Accessories
 
The pair I reviewed came with standard OPPO cables:  A balanced 4 Pin Neutrik and a 1 meter single ended 3.5 mm cable for use with portables.  This is really all you would need to listen to both high end amps and portables.  Since the PMx2 uses standard 2.5mm mono jacks as inputs you can easily buy or build custom cables as well.  HiFiMan has been using these same jacks with their latest cans (HE400S, HE-1K & HE-X for example) so a plethora of custom cabling choices should be available.
 
The PMx2 also comes with a denim carrying case badged with the Audio Zenith logo. The case is snug and adds practically no bulk beyond the size of the cans themselves, making it good for travel as well as storage.  I would love to see a hard-sided case in this design.
 
Comfort
 
Weight of cans is of varying importance to people, for me it’s always a factor.  A great sounding can becomes unacceptable to me at a certain weight (I sold my LCD-Xs just because of that).   The PMx2s are edging right up there at my comfort level. They weigh 483 grams (without cable) which places them above many cans but still well below the heavyweights HE-6 and LCD whatevers.    
 
Since YMMV based on weight tolerance, here is a comparison chart of several other cans right in that weight range:
 
 
 
Note the PMx2 are a lot heavier than the stock PMs.  Something was certainly done in there (and I don’t think stuffing the ear pads is the only culprit!)  The design of the headband wears the weight well. The headband is padded nicely if not excessively, say better than Fostex TH900, same as T1, less than Audeze LCD-X.
 
Overall, the weight stops these from being ‘wear them all day, forget you have them on” cans.  I can do about an hour comfortably which is a a big change from the lesser weight of the PM2s. This makes them slightly less ‘portable’ cans, just adding that extra bit of weight you need to lug to work daily.
 
The PMx2 velour ear pads are firm but not stiff.  The oval shape makes them half 'on'-half 'over' the ears for me but they are very comfortable.  I wear glasses and didn’t find that an issue with these phones.  They seem to breathe as well & never became too hot while listening.
 
Sound
 
The PMx2 is a beautifully neutral can with flagship performance in all the right areas and no apparent flaws.  Speed, attack, extension, imaging all hit their marks.  Bass is extended low & tight.  The lower midrange is slightly bass forward but retains the beautiful mids of the underlying OPPO cans.  The high end is there and very well defined, never getting out of control.
 
Required car analogy: This is the high end luxury sedan, and not a sports car. End of analogy cause I hate that ****.  Everything is done very well and tastefully but nothing to extremes.  There is no attempt to performance in one area at the expense of another, just to raise all areas to a unified high.  I could listen to these headphones all day and not have a complaint.  (Except that weight factor of course.)
 
Comparison with Ether
 
The PMx2 bass extends further down than Ether with more of a punch.  The PMx2s upper bass range is pushed slightly more than the Ether, occasionally making its sound a little less spacious & little more fat and flat in comparison.  Accordingly, the Ether’s high midrange sometimes seemed more open. The PMx2 treble extends up as high as Ether or above though neither pushed into ‘airy’ territory in my listening.  (Remember, I’m a big fan of the HD800s).  The Ether is significantly more comfortable however, weighing in at over 100 grams less than the PMx2.  The ear pads on Ether are much more squishy & comfortable as well.
 
Inevitable comparison with PM2s
 
The PMx2 extends the range of the PM2, bringing the bass lower and the highs higher.  The extra bass pushes the midrange slightly more forward, but not unpleasantly.   The higher top end opens the can up more on tracks that emphasize that.  Overall there’s a little more zing to the stock cans and a better sound.
 
As a practical matter though this improvement comes at doubling the cost of PM2s.  I say youch again because the price anchoring phenomenon has made me and others I’ve spoken to actually react that way.  Like, out loud.  I get that the cost is probably completely absorbed into the work effort required for tweaking (let alone the parts) and I don’t think that reaction would be there without the PM2 reference point, but there it is.  Mentally this makes a hard sell, especially as the finished product doesn’t produce the bragging rights of being a ‘killer’ in any one area.  Instead you get “more neutral”.  Hrrmm.  As a headphone lover I expect more sizzle when I pay for the all the extras, maybe.
 
The Conclusion
 
Alex at Audio Zenith has taken a very good headphone and made it better, at the expense of weight and, well, expense.  People looking for a high performance, ‘neutral’, all around can should have a listen. These are one of the few cans (the only can?) I can think of that specifically fills that bill.  I'm thinking these would make a good gift for the non-headphone person asking for the “best” all around, high-end can that does everything right and could still be considered a portable. 
 
I would not choose these as my only high-end can, specifically because of the weight and because there are multiple other serious contenders around this price point these days that are lighter, more comfortable, and shine more in various areas.  I’m also not a fan of the decal look; perhaps a special request not to decal the can or to include them separately could be accommodated.

Pros: Build quality and sound quality are top notch, I have no qualms with either.
Cons: Cost, non removable pads.
Tonal Balanced: Balanced
Style: Open circumaural headphones
Listening Set-up: Musicbee (FLAC) -> Matrix HPA-3u
Cost at Time of Review: $1,400
 

Reviewing Process

I’ve had the PM-x2 for a bit over a month now and have put significant head time on them. Over the course of my time I feel that I have gained a solid understanding of the sound and build of the PM-x2 and feel confident sharing my opinion. With that said this review is my opinion and I encourage readers to demo a product when available before buying.
 
Thanks to Alex for graciously allowing me to borrow this pair!
 

Build Quality & Fit

 
Build
To put things simply the PM-x2 are built extremely well from top to bottom with no worries of durability based on the review pair that I’ve had for a month. The headphone is mostly constructed of metal with plastic being only apparent on the outside of the earcup. No squeaks, no creeks, the earcups swivel 90* each way with no groans or resistance and the sliders adjust the headband with a firm click. I have no qualms about the quality of the build here though I am disappointed that the pads are not removable, at least not in a quick on/off way.
 
Fit
The PM-x2 fit rather comfortably around the ears with their plush velour pads with a modest amount of clamp. The horizontal pressure is adjusted nicely to my head, though my ears are nearing the drivers. The metal construction adds to the weight though and downward force is certainly noticed. The headphones aren’t uncomfortable, but they never disappear once on my head; there’s simply too much downward force for these to disappear on the head. Neither comfortable or uncomfortable, the PM-x2 are able to be worn for hours at a time without any discomfort.
 

Sound Quality

 
Bass
A lot of people believe that a neutral or balanced headphone is one that lacks bass, but this is not true. A truly balanced or neutral headphone should have a linear bass response that digs as low as the ears can hear, and that is what I hear with the PM-x2. Using the bass shaker test I feel a visceral rumble at the lowest frequencies with a linear bass response up to 200hz and back down. In real world listening the sub-bass is textured in such a way that sounds buttery and thick without sounding sluggish; mild rumble in the deepest notes while maintaining clarity and control. The thick qualities of the PM-x2’s sub-bass make it a perfect complement for the sub-bass driven song Sleep Sounds from Jamie xx, or the Jon Hopkins album Immunity. When tested with James Blake’s Limit to Your Love I feel that the PM-x2 handles the rapidly pulsating bass sequence rather well, but I prefer the PM-x2’s sub-bass with more slower plodding sub-bass driven songs.
 
The midbass is smooth with a touch of warmth, coming off mildly thick but never intrusive. Kick drums are punchy, albeit a bit rounded in texture, while bass guitars are thick and controlled. There’s perhaps a slight sense of hump here, but I may be overthinking things. What I do know is that the qualities of the midbass have sounded great with Madonna, Dawes and Kendrick Lamar alike making the PM-x2 a rather versatile headphone as it carries energy from pop music while sounding lifelike for the alt-country acoustic drums of Dawes.
 
Mids & Highs
The midrange is stellar; this is the most natural sounding midrange that I’ve heard to this date and it does so effortlessly. Every instrument within the midrange sounds phenomenal, but the PM-x2 shines brightest with well mastered acoustic tracks, a favorite of mine being Fleetwood Mac’s Never Going Back. The midrange is quick to decay which allows for each string pluck to be clearly discerned, never sounding cluttered due to sluggishness. Tonality is spot on, with each instrument sounding natural, there are no signs of coloration to my ears. The midrange also has fantastic resolve which allows me to hear the small details like strings buzzing, or the hand changing positions on the fretboard to a great level, furthering my immersion within the song.
 
The midrange reminds me a lot of a refined Sennheiser HD600; improving upon clarity and resolve while maintaining a natural tone throughout.
 
The highs are clean and balanced well with the mids, extending without signs of grain. There’s a lack of air in the highs, though they don’t sound confined either. Neither forward or laid back, the highs are presented as natural and effortlessly as the midrange is.
 
Presentation
The soundstage of the PM-x2 is rather wide, though not airy, which can give it a bit more of an intimate sound than something like the K701. What the PM-x2 lacks in width it makes up for in separation, depth and accuracy of imaging. I haven’t listened to something yet where the soundstage was cluttered, even Modest Mouse’s Teeth Like God’s Shoeshine which is a lo-fi recording that gets rather hectic at the end. A touch of air would be nice, but otherwise I have no complaints here.
 

Conclusion

The PM-x2 are a headphone that I consider to be a direct upgrade from the Sennheiser HD600 and potentially end-game for many people. While the Sennheiser HD800 is a more resolving and airy headphone I enjoy the slight warmth and musicality of the PM-x2 over it. The PM-x2 are balanced while carrying respectable authority in the lows, a truly easy to listen sound signature that is immediately enjoyable without lacking resolution.
 
The PM-x2 are the total package: build quality, aesthetics and sound quality. The only hang up I have with the PM-x2 is the price, but that issue is not one that I have exclusively with the PM-x2. The PM-x2 are a totally valid option considering comparably priced headphones such as the HD800 or LCD-X and between the three they are what I would choose.