OPPO PM-3

Introduction
 
The OPPO PM-3 is my first delve into both OPPO's headphones, and planar magnetic headphones in general. Being fairly new to the hi-fi audio crowd, the $400 I forked over for these cans are the most I've ever spent on a pair of headphones, and I did not do it lightly. My wallet is still a little on the thin side, but I am happy to report that these headphones well warrant their price, and they are really are great.
 
Packaging, Accessories, Etc.
 
The PM-3 comes in a stylish dark grey/black box that has a sort of grain feel to it with a silver OPPO logo placed in the bottom right corner of the top. Inside the box is a hard denim carrying case which houses the headphones themselves. The headphones come with a 3 meter cable and an additional cable for portable use, chosen by the buyer while checking out. I chose the android cable for use with my S5, but an Apple variant and a straight cable are also available. The extra cable comes in it's own packaging, while the longer cable comes in a small drawstring bag which also holds the included 3.5 to 1/4 adapter.
 
Headphones
 
Build Quality
 
The headphones themselves are a combination of metal, plastic, and synthetic leather. The headband and the parts that hold the ear cups are all metal, but the ear cups themselves are plastic. The back of the ear cups have a nice brushed metal look, which I like much better than the original glossy design that OPPO had on the prototypes. The headband is not hinged, and therefore it does not fold inward, but the PM-3 does fold flat either way to become more portable. The ear pads and headband I believe both use the same type of synthetic leather, which, might I add, is the most comfortable synthetic leather I have ever felt. The ear pads are nice and thick while the material within is supple and soft, which makes these headphones very comfortable to wear. While I don't know the exact measurements of the openings on the headphones, I can definitely say my ears fit very comfortably inside the headphone, albeit with little room to spare.
 
Comfort
 
To reiterate what I stated above in the Build Quality section of this review, I find the PM-3 to be very comfortable. The clamping force is a little high, but the pads are soft and thick enough to sort of mold onto the head. My ears fit within the openings on the ear cups, so that also is a big plus.
 
Sound Quality
 
Overall the sound quality of the PM-3 is very neutral, though a teensy bit of coloration was added to give a bit of excitement to the signature. I find the sound signature to do everything very well, but even within the category of "very well," there are still certain things the PM-3 does better than others.
 
The highs on the PM-3 are smooth instead of sharp, which means that you will be hard pressed to find someone who finds these headphones fatiguing in regard to treble. The tradeoff, however, is that they are not as airy and clear as some other headphones. Even though the highs are smooth, this is definitely not an indication that the PM-3 lacks detail or clarity, or that OPPO threw these characteristics out the window when designing the PM-3, because they definitely do exhibit good detail and clarity. I believe the designers of this headphone tried to find a sweet spot between an overly bright treble and a veiled treble, and I believe the resulting signature is very pleasing, though your opinion may differ.
 
The mids definitely stand out on these headphones, as vocals and stringed instruments are clear, detailed, and accurately represented. I discovered new things I had never heard before, and even when I didn't, I was still blown away by how well each instrument presents itself separately instead of being blended into the track. Suffice to say, if you like music with a lot of instrumentation, you are in for a treat.
 
The bass is a bit mixed for me, as it is very tight and accurate, but I feel as though it is a little lacking in respect to the rest of the frequencies. The extension is very good, with most of the low frequencies being picked up without a problem, but I found myself wanting a bit more of a slam in some songs. That being said, I would rather have too little bass than too much bass, so I am completely happy with the signature in that regard.
 
The soundstage is another place where the PM-3 falters a little. The stage definitely isn't as wide as an open back pair of headphones would be, but when the noise isolation and ear cups are taken into consideration, it is much easier to forgive this shortcoming. Even at loud listening volumes, these headphones leak little to no sound.
 
Portablility
 
These headphones can definitely travel. They hit all the checkboxes that one could have for a pair of headphones to leave the house. The PM-3 are stylish, they are easy to drive, they isolate excellently, and they come with a very nice carrying case.
 
Amplification
 
The PM-3 is rated at an impedance of 26 OHMs, which means that any smartphone or ipod should be able to sufficiently drive them. In a completely silent room on my S5, I can get to around 11/15 before I have to turn it down because it is too loud, and I listen to music loudly. They might not go loud enough unamped if you were to use them in very loud scenarios.
 
I don't have much in the ways of amplification, but I have been using a portable Fiio E6 with my phone, which can actually make the PM-3 go VERY loud. The second bass boost setting on the E6 (the blue one) is also very good with the PM-3. At home on my desktop I use my O2, which definitely brings out more bass and detail in the headphones. In comparison to just the S5, both the E6 and the O2 make the headphone sound better.
 
Conclusion
 
The OPPO PM-3 is a wonderful headphone definitely worth it's price of $400. With it's wonderful build quality, stellar sound quality, and great portability, the PM-3 nails every mark it sets out to. Though the bass could be a little more present, and the soundstage a little wider, these are minor gripes in comparison to the PM-3's many strengths. If you are looking for a great portable headphone, I would highly recommend these.
 
This is my first review on Head-fi. If you have any advice or suggestions, please let me know.

Oppo PM-3 Review:
 

Intro:
Specializing in high end blu-ray players, Oppo Digital is a relatively new player in the planar magnetic headphone niche, comprised mainly of Audeze and Hifiman (along with some Fostex T50RP modders & Fostex reexploring the tech with their new open TH500). In 2014, Oppo released the PM-1 as their flagship and the more affordable PM-2 with the same sound but less premium materials to much acclaim in this community. Their focus on a stylish design built with luxurious premium materials with an easy to enjoy, easy to drive, forgiving warm rich sound found many fans. I had the chance to demo the PM-1s which I was greatly impressed with, but ended up choosing the HE-560 for my primary pair of headphones.
 
With the recent trend to lighter orthodynamic headphones, the possibility of truly portable orthodynamic headphones seemed ever closer. Finally, amidst much excitement, Oppo has released the first pair of truly portable planar magnetic headphones in the modern era: the PM-3 at $399. I am personally a big fan of planar magnetic headphones and I am really excited about the recent advances & developments made in this field.
 

Image of the packaging
 
Tech: The Oppo PM-3 is a closed over-ear pair of headphones with a 55mm diameter planar magnetic driver using a FEM-optimized symmetric push-pull neodymium magnet system. It has a 7-layer diaphragm with double-sided spiraling coils. The frequency response ranges from 10 Hz to 50 kHz.
 
Design: Build quality is excellent following Oppo's track record. The headphones are made up of metal, high-quality plastic, and synthetic leather. Has an extremely premium feel to it. The headphones can swivel either direction to fold flat. The swiveling action of the earcups are buttery smooth and the sliding action of the adjustable headband feels quite solid as well when you click it into place. The Left and Right channels are labeled above the swivel mechanism with a L & R. A thoughtful touch is a tactile bump under the L label, so you can tell whether you are wearing the headphones correctly without removing them. The single 3.5mm input socket located on the left earcup has a very thoughtful gasket design that gives you very solid click when you connect the cable all the way in. The connection is quite solid and the cable will not be pulled out of the headphones accidentally. Do note that the sound quality suffers if the cable is not fully properly connected. The headphones do look quite stylish in both black and white color options with the metal accents. Extremely beautiful pair of headphones. Overall, a very premium finish and gorgeous design that is typical of Oppo headphones.
 
One thing of note is that many of the other competing headphones in the $400 price range do use real leather as opposed to synthetic leather. The synthetic leather used in the PM-3 do seem a lot nicer than the pleather used in most competing headphones. If I did not read that they were synthetic leather, I honestly would not have known it wasn't real leather. Also, the earpads are non-user removeable, but can be replaced by Oppo.
 

 

 

 

 


 
Comfort: Comfort is extremely excellent. Clamping pressure is firm, but not tight. Enough force that the headphones feel very snug on your head and will not fall off even with some extreme movements. Very comfortable fit for me. Oppo rates the clamping pressure at 5 Newtons. The headband has adequate synthetic leather padding so I felt no discomfort or pressure on the top of my head. Due to the extremely light weight of the headphones at 320g, I could wear them for really extended periods of time without any neck discomfort (unlike heavier ortho headphones like the old Hifiman HE-400 or the Audeze LCD-X). The headband is adjustable & I wear mine at 3 notches up. The headband adjusts out to 12 notches. There isn't any markings for the notches, but the headband clicks solidly into place as you adjust it, so your fit setting will not randomly change while in use. I initially had some reservations about the depth of the earpads as my ears are extremely sensitive. However, the depth and dimensions of the earpads at approximately (H:57mm x W:35mm x D:17mm with my measurements) was adequately deep & large enough for me to prevent my ears from brushing up against the interior of the earpads or the driver housing. The lining of the earpad over the driver is quite soft with foam rings circling the driver, so even when I pushed the earcups against my head to simulate too shallow of a fit, my ears did not hit any hard surfaces and the fit was still quite comfortable. The earpads are made of synthetic leather and are quite soft and plushy but do not compress down too much when worn, so the earpads still gave a lot of clearance for the tips of my ears. The breathability of the earpads are much better than most other synthetic earpads and my ears never felt too hot or sweaty with them on. I do live in a hot climate as well. I've had problems in the past with sweaty ears & a stuffy feeling with the pleather of headphones such as the ATH-M50x and the Sony MDR-1R, but I have not experienced this issue with the PM-3.
 
Do note that comfort judgments are quite personal, so ymmv. However, the PM-3 is among one of the most comfortable closed portable headphones I have tried. Should be extremely comfortable for the vast majority of people. As a point of reference, the most comfortable closed portable headphones out of the ones I have tried (imo) are the Sony MDR-1A/MDR-1R. The PM-3 are significantly more comfortable for me than the ATH-M50x due to the nicer soft & breathable synthetic leather used and the deeper earpads.
 
Accessories: The Oppo PM-3 comes bundled with two cables: one 3m cable and one 1.2m portable cable (available as a 3-button Apple remote/mic or 1-button Android/Windows phone remote/mic or a plain cable with no remote). There are extremely few over-ear headphones that offer 1-button Android remotes (I can only think of the V-Moda M100), so that is a really nice plus for Android users. Both cables terminate on both sides in straight 3.5mm jacks. The longer cable has a screw-on terminal to attach to the included screw-on 3.5mm-to-1/4 adapter. The cables are well-built and not prone to tangling. There is a Oppo-logo velcro wrap for the long cable that can serve as cable management. There is a small microfiber cloth bag included that can fit the cable and adapter. A sleek flat denim hard carrying case is also included. The headphones can fit into the case with the cable attached, but the cable needs to bend at a sharp angle that may put undue stress onto the connectors. I would recommend removing the cables when placing into the case.
 

1.2m Cable with Android One-Button Remote/Mic Cable
 

3m cable with adapter attached & velcro cable wrap
 

Microfiber small carrying bag

 
I feel like the included travel case is a huge plus for these headphones! It is a extremely useful accessory to protect and store your headphones during portable usage. The majority of portable closed headphones even up to the $400+ range do not include hard carrying case. Even the new recently released $400 premium closed portable headphones (MH40 Over Ear & BO H6) only come with a soft cloth case. I do strongly feel at the $300+ price point, a hard case should definitely be included. This is a very thoughtful and welcome addition by Oppo.
 

 

 

Images of the included denim hard case
 

Portable usage: These headphones are extremely well optimized for portable usage!! Easy to drive with an impedance of 26 ohms and a sensitivity of 102db. Very comfortable to wear with a very light weight of 320g. The design is very streamlined and stylish with sleek earcups that do not protrude out at all. They are stylish enough to wear outdoors and in public. The headphones fold flat in both directions which allows for comfortable fit when worn around the neck and fits snugly into the included hard case. Excellent passive noise isolation and no sound leakage at all during normal listening volumes. There is hardly any sound leakage up to painful listening volumes.
 
Noise Isolation Tests:

1. Sound Leakage: From a 10 feet distance, the PM-3 is still totally silent up to 11/15 volume on the Samsung Galaxy S5. You begin hearing some noise leakage at 13/15. My normal listening volumes on the S5 is 8-10/15. From a 10 feet distance, I could turn the Lyr 2 volume pot up to the 1 o'clock  position before hearing any noise leakage. My normal listening volume on the Lyr 2 is 9 o'clock for the PM-3. For my hardest to drive headphones, the HE-560, I never go beyond 11-12 o'clock for normal listening volumes.
2. External Noise Isolation: While playing music through the PM-3 at normal listening volumes, I could not hear any external music playing from my Samsung Galaxy S5 at full 15/15 volume from a 10 feet distance. With music playing on the PM-3, it completely masks background noises like the A/C unit fan, the stove vent fan set on high & microwave at a 15 foot distance, and my S5 playing a youtube clip of an airplane jet engine at full volume (link). Voices are also muffled and indistinct. Without any music playing, the PM-3 muffles outside noise approximately 30-50%.

 
Sound Quality:
 
The PM-3's sound signature sits nicely right in between the HE-560's extremely neutral presentation (I consider the HE-560's sound signature to be almost perfectly neutral, though some may consider a tad bright) and the LCD-X's darker bassier version of neutral. Very balanced and well-rounded. I would say perhaps a tad bit emphasis on the mid-range and a subtle smoothness over the treble to prevent too much brightness. Treble is not as crisp and airy as the HE-560, which makes the PM-3's treble sound much smoother and not as sharp. This does make the PM-3 quite forgiving and it does not display any hint of sibilance even on my poorly mastered tracks. The sound signature is actually quite close to the Massdrop AKG K7xx**, which I personally consider to be a very close-to-perfect representation of neutral and an amazing value for its sonics at the $200 price point. I think the PM-3 could pass off as a closed version of the K7xx. Overall sound is quite natural to my ear.
 
The mid-range of the PM-3 is definitely one of its greatest strengths. Very articulate and clean with a good sense of tonality. Piano notes are quite realistic and classical music really excels on these headphones. Female vocals, male vocals, guitars, violins, and trumpets all sound extremely realistic. (Those are the sounds that I have heard live the most so can assess realism better). I really enjoy the way strings are presented on these headphones, you can often even hear the subtle details of the musician's fingers plucking the strings. 
 
The bass is quite tight and clean (no excess bloat or over-emphasis). It is well-balanced to the rest of the sound signature. I would estimate a very subtle bass bump over the "technical ruler flat neutral measurement" as typical of most headphones (in a similar vein to the bass boost of the K7xx - I do believe it to be approximately by the same amount, maybe subtly more due to the additional bass reverb from its closed design). I do think this results in a very natural sounding sound signature and I personally view this sound signature to exemplify neutral. Bass notes are adequately tight with the characteristic planar speed and linear extension. Very linear bass extension that goes quite deep into the lower frequency range, picking up the low frequency rumbles and textures very well. Bass is strong and visceral when the recording calls for it, but never over-emphasized or over-powering. The bass does not bleed into the rest of the frequency response at all. Bass does have enough weight and impact for my listening pleasure. 
 
The treble has the characteristic Oppo house sound. It is a very smooth non-fatiguing treble (that I imagine Tyll would probably immensely enjoy). Not as sharp, crisp, and airy as my HE-560 or K7xx, but it is a very enjoyable presentation of treble. You do lose that extra sparkle or micro-treble detail of the HD800 has with the PM-3's presentation, but considering the numerous complaints for the unnatural brightness of the HD800, I can't disagree with the tuning choice for the treble. (note I personally don't find any issue with the HD800's brightness, but I do think that it is too bright to be a true neutral realistic portrayal of instruments). The tuning of the treble of the PM-3 is very safe and is definitely not overtly bright. Maintains a good level of clarity and detail. I do think the treble of the PM-3 do sound very "sweet" (never get any strident or piercing notes).
 
The overall speed and control of the PM-3 is one of its greatest sound quality assets. The PM-3 is very fast with every note presented quite tightly with adequate spacing. Great transient response with a clean attack and decay. It also presents a well-balanced sense of control over the macro and micro dynamics over the whole dynamic range. The subtle and acute changes in volume levels are quite perceptible but maintain a smooth coherency throughout. The PM-3 definitely lean more towards an organic presentation rather than an analytical/clinical delivery due to the subtle smoothness of its treble, the hint of richness in the midrange, and its full-bodied sound. The overall resolution of the PM3 is quite good with a high level of detail retrieval and great sense of clarity.
 
Of course, the sound stage of all my open headphones (k7xx, he-560, lcd-x) are better the closed portable PM-3, but I think that is the trade off for sleek closed earcup design & great noise isolation. The passive noise isolation of the PM-3 are extremely good. The PM-3 does still have good imaging and instrument separation, just a smaller sound stage compared to open headphones (typical of closed headphones). I would say the sound stage of the PM-3 would probably not be lacking in comparison to other closed headphones (perhaps the k550 will beat it in terms of sound stage, but I categorize the K550 of having the best sound stage of any closed headphones I have ever heard). I would categorize the PM-3 as having a more intimate presentation. However, this does not mean that the PM-3 is lacking in focus, instrument separation, or imaging. The PM-3 actually images very well and you can distinctly place the location of each instrument and singer. The imaging is quite realistic throughout as during a Yiruma piano track when he began to speak, I could place exactly where he was in the room. During orchestral pieces as well, I could distinctly hear where each instrument was. I would say that primary distinction in sound stage is that the PM-3 does give you the feel of listening in a smaller room or crowded club as opposed to a concert hall or outdoors concert. The stage seems a bit smaller and you feel like you are sitting closer to the music in comparison to my open headphones. Do remember that my comparison of sound stage of the PM-3 is against open headphones (K7xx, HE-560, LCD-X) that have the best-in-class sound stage out of any open headphones! A more fair comparison would be against other closed portable headphones, but unfortunately, I do not have any on hand to do a direct comparison against.
 
Measurements: http://www.innerfidelity.com/images/OppoPM3.pdf (credit: Tyll Hertserns)
***Added onto my review on April 9th, 2015. I have not edited my sonic impressions after viewing these measurements***
Reference here for frequency response correlations to instruments and audiophile terms. (credit: Independent Recording Network)
 

***Please note that comparing measurements from different sources is not as reliable due to differences in measurement set-up. Compare frequency response curves from the same source for the best results. Full list of all headphones measured by Tyll: http://www.innerfidelity.com/headphone-data-sheet-downloads***
 
Direct Comparisons: (the links take you to the head-fi review page for each product)
 
Against the Massdrop AKG K7xx: Biggest difference is that the K7xx has a more spacious presentation compared to the PM-3's more intimate presentation. The K7xx has excellent sound stage for open headphones, so it is not too fair to do a comparison in that aspect. The K7xx does indeed win in the sound stage department hahah. The treble is the next difference. A smoother treble on the PM-3 compared to the airy treble of the K7xx. Approximately the same amount of bass quantity, though perhaps a subtle bit more on the PM-3.
**Note: The AKG K7xx is a special edition headphone based on the AKG K702 65th Anniversary Edition offered by Massdrop.
 
Against the Hifiman HE-560: Similar differences as with the K7xx vs PM-3 comparison. The HE-560 does have a lot better detail retrieval, speed, resolution, and much larger sound stage. Spacing between notes is more pronounced on the HE-560. Much crisper, airy sound on the HE-560. Less bass quantity on the HE-560.
 
Against the Audeze LCD-X: LCD-X has more bass presence, impact, and quantity (more bass emphasis compared to the PM-3) & perhaps a subtly more 'sparkly' treble, but the PM-3 do hold their own in terms of sound quality. Quality of mid-range is quite similar as the PM-3 really excels in the mid-range and provides a similar richness to the texture here. The PM-3 do share the organic tonality of the Audeze headphones while sounding more neutral to my ear. The speed of the PM-3 is quite comparable to the LCD-X. 
 
From memory against the PM-1: I do believe that the PM-3 are actually tuned to be more neutral than the PM-1s. I remember that the PM-1s had a lush, smooth, rich texture and a lot of added warmth with very full bass notes with longer decay times (not exactly bloated, but much fuller presentation than the tight distinct lean presentation of bass notes of my HE-560s). This trait on the PM-1s was quite enjoyable, but did make it seem like you threw a warm fuzzy blanket over the recording. The PM-1s seemed to lose a bit of detail, crispness, airiness, and resolution in comparison to the other planar magnetic flagships. The resolution of the PM-1 was excellent, but the warm presentation shifted to focus more to the texture of notes rather than the individual notes and micro-details. The PM-3 do not share the PM-1's warm presentation, but rather has a cleaner, more neutral presentation. The PM-3 also does not have that extra warm texture added to their sound signature, which I personally prefer. It seems like a trade-off with that fuzzy warm rich feeling to the texture but gain a bit more spacing between notes (better attack/decay) & a better sense of detail. Hard to really comment on the exact differences in detail retrieval, micro-detail, and resolution without a direct comparison. Oppo headphones have not been known for their sound stage, and I would approximate that the sound stage of the PM-1s and PM-3 are quite close and comparable. I do remember the PM1s sounding quite intimate, and I do think the PM-3 have a similar presentation. The Oppo house sound also has a very smooth treble rather than a sharp and crisp presentation, so the PM-3 is akin to the PM-1 in that aspect as well.
 
***Update 4/9/15: comparisons against the Alpha Prime, Closed EL-8, and AKG K553 coming soon***
 
Amplification: I tested the PM-3 unamplified through my Dell XPS m1530 & Samsung Galaxy S5 against the Schiit Bifrost+Lyr 2 combo & Bifrost+Woo Audio WA7+WA7tp. Did direct by-ear-volume-matched non-blinded comparisons of short segments of songs that I am intimately familiar with (spent the most time using Heartbeat by Vincetone & Canon in D Major). Switching between different set-ups took less than 5 seconds.
 
I found that the PM-3 performed the worse from my 2007 Dell laptop with a little bit of roughness to the details, a slightly grainy edge to notes, and a looser bass response. (could possibly be due to an issue with my laptop's headphone out or sound card though). Sound was noticeably improved on the S5 with a better overall balance of the frequency response, cleaner details, faster articulation of notes, and a tighter bass response. I do strongly believe that the PM-3 will perform well using most modern day portable devices. The PM-3 do scale up nicely with the addition of a mid-entry amplifier and dac. (unfortunately, I no longer have any entry-level budget equipment to test with). I would say the most noticeable difference was increased bass presence/impact, wider sound stage, richer texture, and a higher level of resolution for micro-details. I had difficulty confirming the exact subtle technical performance differences between the Lyr 2 and WA7, though the WA7 does have an overall warmer presentation. With the refined smooth tuning of the PM-3, I doubt that they will be very picky with external components.
 
***Update (4/9/15)***
Portable Amp/Dacs: I tested the PM-3 with the Resonessence Herus and Oppo HA-2 individually on my S5 and laptop. Greatly enjoyed both pairings and they were adequate to drive the PM-3 without any noticeable clipping. Improved detail resolution and sound stage with both the Herus and HA-2. Precision of the imaging is stellar on both portable devices. The Herus has a brighter presentation than the rest of the dacs I own. This pairing can help improve the treble clarity and sharpness of the PM-3 without any excessive edginess. The Herus would be a good match if the treble presentation is too smooth or recessed for your personal tastes or if you like to subtly dial down the warmth in the sound signature. The PM-3's tuning and presentation prevents the sound from ever getting piercing or strident even with a bright dac. Link to the head-fi Herus thread here. I am still getting familiar with the HA-2; may comment in more detail on its sound later. Initial impressions are extremely positive and I feel that it is a great pairing for the PM-3. So far, the HA-2 does not appear to significantly alter the PM-3's overall sound signature to my ears, but it does improved the overall clarity throughout the frequency response. I immediately noticed improved sub-bass quality, deeper lower frequency extension, and better defined solid bass impact with the HA-2. The HA-2 is more revealing of subtle micro-details in the texture and improved the overall tonality with a realistic weight and presence to the notes. The bass boost feature provides an extremely clean bass 5dB boost frequencies below 100 Hz that tapers to 500 Hz. There is no muddiness or bleeding into the rest of the frequency response. You actually cannot hear a difference in the sound at all with bass boost on/off if you play music that does not have any notes below 500 Hz. I normally have the HA-2 set on low gain, no bass boost, volume pot at 1-2 out of 5 with the S5's volume maxed out. The HA-2 can even drive my HE-560 without any clipping to my preferred listening levels (maxed out volume on the S5 with analog volume pot at 2-3 out of 5 on high gain). Do note that precise volume-matching was a lot harder to do here with the Herus on the S5 having large volume steps, while the HA-2 allows extremely precise fine-tuning of volume levels with the combination of the Sabre dac chip's bit-perfect internal digital volume control and analog volume pot. There is no digital signal processor in the HA-2 and the bass boost is performed by pure analog audio circuits for a clean signal path. Link for HA-2 head-fi thread here.
***End of Update***
 
I will refrain from estimating the exact percentile of improvements in this section as I know that different people have different sensitivities to the sonic changes from different equipment. I am comfortable saying that there is a noticeable difference adding an mid-fi amplifier and dac during a direct back and forth comparison, but they do perform admirably unamped from my smartphone. Additional gear not required to thoroughly enjoy the PM-3 (imo).
 
From my personal experience, I do personally feel like even the best most resolving headphones only scale up to maybe 5-15% with the addition of external components generally. The overall sound signature and technical performance of the PM-3 was largely consistent in a broad sense throughout different set-ups. I never felt like there was anything lacking in terms of sound quality regardless of set-up, but I did eventually notice variations, subtleties, and improvements after extended direct comparisons. I always recommend people unhappy with their sound to switch headphones rather than fiddle with external components. However, if you are generally happy with their sound signature and performance, the PM-3 will go that extra mile with additional investments in your overall set-up.
 
Value Judgment:
You will be paying a premium for these headphones and these headphones do indeed offer premium build quality, design, and sound. I consider these to be in the upper mid-fi portable closed headphone category. The overall mid-fi portable closed over-ear headphone category ranges from $200-$500.
 
I consider well-reviewed $200-$300 options to generally be satisfactory for portable usage and provide a great value for sound. There are indeed other options that offer a more competitive value if purely looking at it from a dollar per sound quality perspective. Examples include the K545 (sub-$200 on sale), K551 ($200ish), Momentum Over-Ears 1st generation (can be found on sale for $150-$200 nowadays), and HP50 ($300) for great high quality sound with a neutral sound signature. 
 
I generally think that $400 headphones are often simply over-priced for their sonics in comparisons to competitors. The more expensive $400 headphones often do not have that much of a sonic improvement over their less expensive brethren, and I do feel like you are simply paying more for the brand name, build quality, and difference in sound signature, rather than sound quality. I do personally feel that way about the B&W P7 and Masters MH40 from my demoing experience with them. I have not had the chance to listen to the new BO H6 yet.
 
From my audio memory (so take with a grain of salt), I will say the PM-3 definitely greatly technically outperform the ATH-M50x, V-Moda LP/M80/XS/M100, Sony MDR-1R/MDR-1A, Ultrasone Pro900, Yamaha Pro500, and P7 (though those headphones may be preferable for some people looking for their specific coloration of the sound signature). The PM-3 significantly outperform the ATH-M50x (a classic reference point for good-valued headphones) in terms of comfort, design, and sound quality. The PM-3 have a more neutral well-balanced sound signature, better imaging/sound stage, quicker transient response, and greater detail resolution, though the ATH-M50/M50x does have a fun v-shaped sound signature that I greatly enjoyed. I do also personally believe the PM-3 also outperform the K545, Momentums gen1, and MH40 (specifically in terms of realism, overall balance, speed, detail retrieval, and resolution). I do feel like the sound stage of the AKG K550/K551 does best the Oppo PM-3 though. The K550/K551 have the best sound stage for a closed headphone that I have heard, though they are unsuitable for true portable usage. I have not gotten a chance to run direct blinded volume-matched comparisons against other closed portable headphones yet, so it is hard for me to say talk about the definite amount of sonic improvements in comparison to the other strong offerings in this category. (note: all the headphones mentioned above I have either owned or extensively demoed & these are my personal impressions so ymmv)
 
The PM-3 does offer significant sonic improvements over the more value-oriented options, but you are now definitely in the area of diminishing returns. I do personally find these headphones to be worth the premium price for me, but I would recommend you to do your own listening evaluations.
 
For shoppers interested in planar magnetic headphones at this price point that do not require noise isolation/portable usage, I would highly recommend checking out the Hifiman HE-400i ($499 msrp, $425 open box at razordog). I greatly enjoyed the HE-400i and feel like they offer a tremendous performancerice value. The other open planar magnetic options in this price range include the HE-400, HE-500, Fostex TH500, and PM-2. For people interested in a closed-back planar magnetic for non-portable home usage and require noise isolation, there is the $1.8k Audeze LCD-XC and Mr. Speaker offers modded Fostex T50RP ($299 Mad Dog, $449 Mad Dog Pro, $599 Alpha Dog, $999 Alpha Prime) that receive a lot of positive feedback around here. Audeze has also recently released the $699 EL-8, available in open-back or close-back configurations, that will be a good option to consider for at home usage. The extreme weight (460-480 grams) and bulky larger size of the EL-8 would make me hesitant to recommend them for true portable on-the-go usage. I will hopefully get the chance to demo them in a few weeks and run some direct comparisons, so I will update this review after that. After that, the only planar magnetic headphones currently available on the market are the premium flagship-type options from Audeze (LCD-2/LCD-X/LCD-XC/LCD-3), Hifiman (HE-560/HE-6/upcoming HE-1000), Oppo (PM-1).
 
For people just looking for a closed portable pair of headphones regardless of technology, my personal favorite mid-fi pick is the AKG K545 for the best sound quality per dollar value. I am also personally greatly interested in trying out the new Momentum Over-Ears Gen2, Audio-Technica ATH-MSR7, and BO H6. For people looking for home usage and do not require portable usage at all nor noise isolation, I would recommend looking into the multitude of stellar open headphones available on the market.

Conclusion:
 
Sound signature is quite close to neutral with a full bodied and well-balanced sound comprising of 'sweet' smooth treble, deep fast bass, and an excellently rich articulate midrange. Sound quality maintains a high level of detail retrieval, resolution, clarity, speed, and imaging.
 
Greatest strength is the attention to detail paid to its portability function: very light-weight & comfy, sleek stylish design, easy to drive, great passive noise isolation, and included hard travel case & bundled remote/mic for your choice of device. Very solid option for people who require portability or noise isolation.
 
Greatest con is that its sound stage does not match the performance of open headphones. I would approximate that its sound stage is at least better than average among the majority of closed backs if not better than most closed headphones. Would require more in-depth direct comparisons though to really rank its sound stage among its closed back peers.
 
A great & very competitive offering even among the extremely crowded $200-$500 closed portable mid-fi headphones niche. One of the most inexpensive planar magnetic options out there for people interested in trying out orthodynamic headphones (prices for planar magnetic headphones start at $300 for the old Hifiman HE-400 and goes up to $2,000 for the Audeze LCD-3). One of the few closed planar magnetic headphones options out there (only others are the upcoming Audeze EL-8, Audeze LCD-XC and modded Fostex T50RPs like Mr. Speaker's line-up). Currently, the PM-3 is the only truly portable modern planar magnetic on the market.
 
Highly recommended for anyone looking for a closed portable pair of orthodynamic headphones with a well-balanced neutral sound signature and excellent overall sound quality!!! 
 
product link: http://www.oppodigital.com/headphones-pm-3/
 

Image of all my gear used during testing