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.

Alex is quite in interesting guy. I spent about an hour with him on the phone discussing his journey and his craft. Honestly, it's a compelling story. The story is well known and has been told before so I won't bother to rehash it in great detail. But let me say that I believe that Alex is passionate and talented and that he has something special to contribute to the world of hi end personal audio.
 
I followed the Oppo headphone story closely from the first mention of the product by Jude when the pm-1 was still very much a beta product. Many of us longed for a company to create a comfortable planar magnetic audiophile headphone that would compete with the likes of Audeze and other Orthodynaic big hitters.
 
When the pm-1 was released, it launched to mixed reviews. While there were many that sang it's praises, there remained a contingent that felt it lacked resolution and fidelity of a true flaship product given it's price.
 
I think that it's fair to say that Alex would fall into the camp that felt like the Oppo headphone did not deliver it's true potential. And in that moment, I suspect, Audio Zenith was born. Alex began his journey with the pm-2 in an effort to get the best fidelity possible from the Oppo drivers. If you feel that the pm-1/2 is good but is somewhat overly warm or lush without an appropriate level of resolution, then the pmx2 may be just what the doctor ordered.
 
The pmx2 is quite a departure from the stock headphone. There is an impressive level of modification in the pads alone. Alex has taken the stock velour pads and created several sections of varying firmness and with sections of channels. My understanding is that the pad modification facilitates a wider more open and airy sound stage that admittedly the original headphone lacked.
 
Listening to the stock headphone and pmx2 back to back, I'll confirm that the modded headphone is certainly more airy and open in it's presentation. The stock offered a more intimate stage where the listener is very close to the music. Some would say that the stock presentation is a bit too close and intimate. In this regard the pmx2 has successfully eliminated the problems associate with the stock headphones constricted sound staging. The modded pads are still comfortable and give up only slight bit of the ultimate comfort that I find with the stock pads.
 
One aspect of the pmx2 that is fairly obvious once you ease into the pmx2 is that the modded version carries a fair bit more weight than stock. Right at 490 grams according to my kitchen scale, the pmx2 gets into the danger zone with regard to be too heavy to be worn for me than an hour with pressure point or muscle strain becoming an issue for me. When I mentioned this to Alex he offered a simple explanation to address the problem. Simply reshape the headband for more clamp. After a few attempts to carefully reshape the headband, I was in business. The extra clamp worked wonders to make the pmx2 comfortable for an hour plus while listening. Although I still find the stock headphones more comfortable, the pmx2 is certainly reasonable comfortable for long listening sessions.
 
The time and dedication that Alex puts into each set of pmx2 is impressive. He states that he doesn't really have a firm time table for completing each pair. He simply works each part of the modification until the headphones are finished. I certainly appreciate his hard work and it was evident from the moment that I put them on for an initial trial run.
 
The sound achieved with the pmx2 is both technically impressive and musically enjoyable. Compared to the stock version the pmx2 is first and foremost more neutral. The stock version is warm and thick with the bottom of the signature colored particularly in the sub bass. The pmx2 reigns that color in and presents and wonderfully neutral and accurate signature.
First and foremost, I'm a mids guys. I listen to a lot of vocally centered music. The mids on the pmx2 are a notch or two better than stock. There are subtle nuances that come through easily on the pmx2 that I wasn't hearing with the stock version. These realistic nuances drew me in to the music and made me listen longer. Simply put, the vocals were more natural and realistic, but they are offered more detail and resolved the recording to a higher degree. Mids are not quite so forward on the mod. They are more 4^th or 5^th row instead or 1^st or 2^nd. I enjoyed this change for most genres.
 
Treble, which admittedly has always been a shortcoming on the stock version, shows more extension and presence on the modded version. Hi hat cymbals are not voiced in a subtle way. In fact they came across with good dynamics and extension when called for. This brought new genres of music into play for me, especially classical and stringed pieces with violin.
 
With regard to mid-bass, it's toned down quite a bit on the mod. Sub bass seems significantly tighter and textured. Overall the modification offers a very musically neutral and more cohesive presentation of the music. So is it worth the cost of admission. I confess that I had doubts going into this audition. In the end, I found myself coming away a believer despite my reservations. The pmx2 is an excellent headphone and makes a good product even that much more impressive.
 
Thanks again to Alex for his generosity to share his product and time with me. I really enjoyed our conversation and getting to know, first hand, how you created this wonderful headphone.
 
 
 
 

Audio Zenith PMx2 Over-ear Planar Magnetic Headphone:
 
*Disclaimer - I am in no way affiliated with Audio Zenith, Oppo Digital, or any public headphone/electronic company. I’m just an amateur enthusiast who works a normal 9 to 5 office job in the import/export field. I usually listen to headphones on average of 2-4 hours per day. My preference is towards slightly warm headphones, with an emphasis on the mids. I was introduced to these headphones at THE Show in Newport 2015, and paid full retail for them directly through Audio Zenith’s website:
 
www.audiozenith.com
 

 
Audio Zenith Background:
 
Founded in late 2014, San Diego, CA based Audio Zenith is a budding headphone modification company which focuses its efforts exclusively on modifying the Oppo PM-2 planar magnetic headphone. While his company has only been around for a little over six months, owner Alex Zaets has been tinkering with Oppo’s planar magnetic headphones for quite some time, as a result of his relationship with Oppo’s lead headphone designer Igor Levitski1. He has been tinkering even longer in the realm of digital signal processing, and previously attended high-end audio shows under the company name of “Acoustic Zen/Million Dollar Sound” to show off his dsp work with. TAS reviewer Robert Greene even went as far as to say, “[Alex's system] was gorgeous, to my ears some of the most beautiful and musically truthful sound at that or any other show. And indeed [he] got the room really out of the system to a startling extent.”3
 
Audio Zenith is the first officially sanctioned aftermarket dealer of modified Oppo headphones. Being a small startup, current production is limited to only a handful of modified PMx2’s per month, and all are modified/tuned to order.  Please contact Audio Zenith for lead times, as they may change based on demand.
 
 
PMx2 Introduction:
 
Pronounced “PM times 2”, the PMx2 headphone is a result of over two years of work, and more than two thousand measurements in an effort to achieve, what Alex considers to be, the perfect reference level sound signature. From fine-tuning the drivers to developing five different zones of pad density, it’s safe to say that developing the PMx2 was a massive labor of love on his part. After spending a few days with the end result, I think it’s also safe to say that his efforts have paid off quite nicely.
 
 

 
Specifications:
 
The PMx2 shares the same specifications as the stock PM-2. 
 

Headphone Specifications
Acoustic Principle	Open back
Ear Coupling	Circumaural
Nominal Impedance	32 Ohm
Sensitivity	102 dB in 1 mW
Clamping Pressure	5 N
Cables	3 m detachable OFC cable (6.35 mm) 1 m detachable OFC cable (3.5 mm)
Cable Connectors	Output: 2.5 mm mono mini jacks Input: 6.35 mm stereo jack, 3.5 mm stereo jack
Weight	PM-2: 385 g (without cable), PMx2: 490 g (without cable)
Included Accessories	Carrying Case 6.35 mm and 3.5 mm cables User Manual
Driver Specifications
Driver Type	Planar Magnetic
Driver Size (Oval)	85 x 69 mm
Magnet System	Symmetric push-pull neodymium
Frequency Response In Free-Field	10 - 50,000 Hz
Long-Term Max Input Power	500 mW according to IEC 60268-7
Pulse Max Input Power	2 W

* credit Oppo Digital 
 
 
Changes vs the Stock Oppo PM-2:
 
- Neutral tuning vs stock PM-2’s warmer signature.
- Custom velour pads, which have been developed to have five different zones of firmness for proper driver placement, seal, and acoustic dampening. *Alex noted that he went through dozens of variations of custom pads to solve areas of uneven air pressure resulting from a circular driver and an oval pad. (please refer to pictures)
- Pads are not removable.
- Driver has an altered magnetic structure, and magnetic field distribution.
- Each driver is tested and matched to the other.
- Minor cosmetic changes such as “Audio Zenith” branding to cover up the stock “Oppo” branding. I’m not really partial to the design, but I don’t think it’s terribly bad either. It still has an attractive, black suit & tie feel to it. 
- Price increase of $700 USD vs Oppo PM-2.
 
Unboxing / Design:
 
The Audio Zenith PMx2 is very similar to the stock Oppo PM-2 in its presentation.  The headphones come housed in same box as the stock PM-2 with only the logo being altered.
 

 
 
Inside the storage box you will find the standard Oppo PM-2 fare:
- Oppo’s denim travel case with the logo being the only thing altered
- Short 3ft cable w/ 3.5mm termination
- Long 10ft sleeved OFC cable, same as the stock PM-2 cable + Audio Zenith branding.
- Soft cable pouch
 

 
 
The headphones themselves share nearly all of the crowd-pleasing aesthetics of the original PM-2 headphones. Although I appreciate Alex’s refined sense of style in not going overboard on altering the design of the already attractive PM-2, I would have preferred an even more subtle branding effort (but that’s just me).
 
The Oppo logos have been replaced with Audio Zenith name, and the adjustment sliders now feature the Audio Zenith logo. Alex points out that the logo serves to not only aid in branding, but also to help the user remember the adjustment position. I find that even though it does help, the issue really wasn’t that big of a deal to me in the first place. In the end, the thing that stands out to me the most is the fact that Alex thought about all these minute details, when I would have just overlooked that aspect of convenience.  Overall the PMx2 keeps all the luxurious aesthetics of the original PM-2, while altering just enough to differentiate it from its former self. 
 
 
  
 
 
 
 
 
Sound Signature:
 
The PMx2 has been tuned for a flat response.  Please don’t make the mistake of assuming flat equals boring, because these headphones are anything but.
The PMx2 is Neutral, exciting, and supremely smooth.
 
 
Oppo PM-2 Frequency Response1:
http://www.innerfidelity.com/images/OppoPM22014StockPads.pdf
 
Audio Zenith PMx2 Frequency Response1:
http://www.innerfidelity.com/images/AudioZenithPMx2.pdf
 
Testing for this review was done on the following set-ups: 
- Macbook Pro > Schiit Wyrd > Woo Audio WA7d (stock sovtek 6c45) + WA7tp (mullard 12au7) > PMx2
- iPod Touch 5g > Oppo HA-2 > PMx2
- Astell & Kern AK100ii > PMx2
 
 
Bass:
 
Rating: 9/10 = classical/jazz/instrumental/rock, 7/10 = edm, rap.  
 
At first I was going to award the PMx2 an overall “8/10“ on the bass, but after some more critical listening I decided to split the ratings for the bass quality based on the genre of music. I think it would be a terrible disservice to these headphones to oversimplify the bass rating when each genre of music demands a different approach to bass.
 
Overall the bass is fast, accurate, and detailed, as one might expect from a planar magnetic headphone.  The mid bass is wonderfully rich when listening to classical, jazz, and instrumental music. It hits the low notes of live instruments to perfection, with no bleeding into the midrange. However, it does lack the gut rumbling low-end extension, and sheer quantity needed to really immerse oneself into edm or rap music. When compared to the stock PM-2, the sub-bass of the PMx2 sounds attenuated (as shown by Tyll’s FR charts).
 
 
Midrange:
 
Rating: 10/10
 
While the PMx2 is tuned flat across the spectrum, the sonic signature is decidedly mid-forward. This headphone really shines when reproducing live instruments and vocals… especially anything acoustic. The PMx2 brings out the best in any string instrument, and listening to the piano is just pure bliss. The mids sound balanced across the entire range, with no section being emphasized more than anything else. It is a true “Reference” headphone in every way in terms of the midrange.
 
 
Treble:
 
Rating: 10/10
 
The Original PM-2’s treble was the weakest part of the headphone’s signature in my opinion. It was rolled off, and overly laid back, leading to a somewhat boring listening experience. I’m happy to say that the PMx2 have remedied this.  
 
The PMx2 is absolutely a "top of the line" product in terms of clarity and precision, while still retaining musicality and smoothness. It is supremely clear, without being clinical or overly analytical at all. It is a world-class mixture of silky smoothness, and just enough sparkle to keep things exciting, but not enough to make the music sound piercing. This is just my personal opinion, but I think the treble is some of the best I've ever heard. It can definitely go head to head with anything out there. This includes the LCD-3, Ether (demo'd at Canjam 2015), HD800 w/ grace m920 (demo'd at Canjam 2015), HE-1000K (demo'd at Canjam 2015). Given that the canjam demos were held in loud, stuffy, and crowded rooms, I'll reserve any definitive judgement on it.
 
The best way I can describe the quality & finesse of the PMx2’s treble is with a cooking analogy.  It’s like a perfectly seasoned dish… Just enough sparkle in the treble to make the music feel alive, and exciting, while not overpowering the whole. It makes you want to sit in for another song, and another. Similar to how an expertly seasoned dish should make you want to take another bite, and another. As everyone knows, too little seasoning and it’s bland, but a pinch too much and it’s completely uneatable.
 
Sound Stage:
 
Rating: 8/10
 
Similar to the stock PM-1/PM-2, the sound stage is more intimate compared to other open backed headphones. I’d liken it being at a small dinner theater show versus at a stadium concert. Still, you can definitely sense a feeling of airiness when compared to closed back headphones.
 
Imaging/Separation:
 
Rating: 9/10
 
While the soundstage isn’t as big as comparable open back headphones, the imaging on the PMx2 is second to none. As long as the recording shows it, you will hear every instrument clearly, and can imagine exactly where they would be. Main vocals seem to float right behind your eyes. I can’t say anything bad about this aspect.
 
 
Headphone Comparisons: 
 

 
 
PMx2 vs Audeze LCD-3:
 
- The PMx2 sounds more forward in the midrange and treble, while being slightly lighter in the bass department.
- Both headphones are excellent in terms of clarity and imaging, with the LCD-3 having a slight edge on the imaging. 
- The PMx2 is also more aesthetically attractive, and comfortable to wear. The LCD-3 is kind of attractive in a steam-punk sort of way, but I wouldn't wear it in public. They are also very heavy, and uncomfortable to wear for long listening sessions (*the aftermarket "Lohb" strap fixes this issue).
- In terms of soundstage, the LCD-3 is the clear winner. The LCD-3 sounds very airy and open compared to the more small theater feeling of the PMx2. 
 
PMx2 vs Fostex TH900:
 
- The most obvious difference is the bass. It is the defining quality of the TH900. It's plentiful in quantity, rich and digs down deep. The PMx2's bass is much more refined and reserved in comparison.  
- TH900 is unabashedly V-shaped, and the PMx2 is decidedly flat. Both have top of the line qualities for their respective styles. 
- The TH900's treble is somewhat sibilant to sensitive ears vs the smoother signature of the PMx2. 
 
PMx2 vs Sennheiser HD650: 
 
- I think the HD650 and the PMx2 share much of the same qualities. I view the HD650 is a slightly less refined, looking and sounding, PMx2.
- Both have fantastic performance in the midrange and treble. The HD650 has an edge on the quantity of bass, but the PMx2's bass is faster, and tighter. 
- Both are top notch headphones regardless of price, but when you do consider the price... the HD650 is the clear winner. It can be found for ~$280.00 usd when on sale at various websites now days. 
- The PMx2 is a great upgrade for those of us who already own the HD650, but didn't necessarily get along with the stock HD700 and/or HD800. *Note I emphasize stock. I've heard some amazing modified examples of the HD800. 
 
 
Conclusion:
 
Overall Score: 9/10
 
The PMx2 is nearly a perfect headphone in my book. It takes an already attractive looking headphone and boosts the sound quality to another level. I would have rated this headphone a perfect 10/10 if it were not for the attenuated bass (one of my favorite parts of the original PM-2), and the small-ish soundstage of the PM-2.
 
Is it worth the msrp of $1398.00 USD?
Yes, if you’re in the market for a top of the line headphone, with a budget to match. If you’re a person who needs that last 10% of sound quality, then absolutely these will satisfy your “upgraditis”. I believe these can hold their own with the current line up of TOTL headphones such as the HD800, Ether, LCD-3, HE-1000 etc., and even be the preferred choice for some (when taking into consideration sound, price, comfort, aesthetics, etc…).
 
No, if you’re on a budget. In this situation, I’d highly…. highly suggest the HD600/HD650 (when on sale for  $225/$280 usd respectively).  The PMx2 is very similar in signature to the HD600, just more refined in sound and looks.
 
 
Critical Listening Song Choices:
*All songs were played through Tidal or ALAC files for testing, but I’ve attached the corresponding youtube links as well.
 
1) L. Boccherini - La Musica Notturna delle Strade di Madrid - Op. 30 n. 6
 
2) Yo-Yo Ma - Prelude from suite No. 1 in G Major for Cello, BWV 1007
- The always amazing Yo-Yo Ma. The cello sounds lifelike and vibrant with the PMx2. 
 
3) Post Modern Jukebox - All about that bass – jazz cover ft. Kate Davis
- My wife loves these guys… ok I’ll admit I kinda like them too. It’s definitely a guilty pleasure. The PMx2 makes the stand up bass and piano sound incredibly life like.
 
4) Stevie Wonder - If it’s Magic
- Silky vocals, great soundstage, and amazing sounding harp.  
 
5) Matoma & The Notorious B.I.G. - Old Thing Back (feat. Ja Rule and Ralph Tresvant) - ** Explicit Lyrics/video is NSFW **
- my current go to song for checking out bass quality.
 
6) System of a Down – Revenga – Mezmerize
- Need a track to test the speed and accuracy of your headphones, while listening to some killer vocals? System of a Down’s surgical precision will satisfy you.
 
7) Dragonforce – Through The Fire and Flames – Inhuman Rampage
- Torture test. Herman Li and Sam Totman on the guitar can be awesome on the right set of headphones, and painful on the wrong set.
 
8) James Horner – Glory – Closing Credits
- RIP James Horner.
 
 
Sources:
 
1) Innerfidelity.com - T.H.E Show Newport 2015 Highlight: Audio Zenith PMx2 
 
2) Audiocircle.com - The Show, Newport 2012
 
3) Direct Q&A with Alex Zaets via telephone.