Oppo PM-1 Over-the-Ear Planar Headphones Reviewed

Published On: July 23, 2014
Last Updated on: March 9, 2022
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Oppo PM-1 Over-the-Ear Planar Headphones Reviewed

Up to now, Oppo hasn't been a brand that is usually associated with personal and two-channel audio. Oppo made its name in video with market-leading DVD players and then universal disc players. However, just as man cannot live by bread...

Oppo PM-1 Over-the-Ear Planar Headphones Reviewed

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PM-1-Side.pngUp to now, Oppo hasn't been a brand that is usually associated with personal and two-channel audio. Oppo made its name in video with market-leading DVD players and then universal disc players. However, just as man cannot live by bread alone, Oppo has widened its manufacturing horizons with two new audio products: the PM-1 planar headphones and the HA-1 DAC/headphone amplifier.

This review will focus on the PM-1 headphones. With a street/list price of $1,099, the PM-1s are aimed directly at the center of the high-performance, premium-priced headphone market. Just as Oppo's entry into the DVD and universal player market created quite a stir, the company's new headphones could cause an equal amount of upheaval among headphone manufacturers. But are the PM-1s a game-changer or merely another competitive high-quality headphone option? Let's find out.

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The PM-1's design is based around its own proprietary planar magnetic driver. This driver has a large 85mm-by-69mm, seven-layer diaphragm that uses a spiraling pattern of flat conductors on both sides of the diaphragm. This scheme increases the headphones' sensitivity and gives them a higher damping factor. The PM-1 has a sensitivity of 102 dB per one mw and a nominal impedance of 32 ohms, so the power amplifier in any smartphone, tablet, or portable music device should drive these headphones easily. This differentiates the PM-1 from other planar headphone designs. The 32-ohm PM-1 was created to be unfussy (as far as amplifiers go) so that it can perform optimally with a wide variety of devices. I used them with a variety of portable devices, including the Astell & Kern AK100 and AK240, Calyx M player, Colorfly C4, iPod classic, iPod Touch, and my iPhone 5. In every case, the mating supplied the PM-1s with more than enough juice to play as loudly as I could stand with ample room to spare, gain-wise.

The over-ear PM-1 has an open-back design created for optimum sound quality and comfort. Most closed-back headphone enclosures add both weight and inevitable "cabinet resonances" that reduce their comfort and fidelity, but open-back designs have their own set of chronic issues. They do very little to reduce the amount of sound that leaks from your headphones into the outside world, and they do not deliver much in the way of isolation. If your primary purpose for using headphones is for seclusion from outside noise and for privacy, a closed-back headphone or in-ear monitor would be a better choice. Given how the PM-1 headphones can fold up into such a compact package inside their travel case, it's unfortunate for audiophiles who need to travel light that, given the PM-1's open-air design, they can't serve as a universal headphone solution. But augmented by a pair of high-isolation in-ear monitor-types, such as the Etymotic ER-4 or custom in-ear monitors like the Westone ES-5, the PM-1 headphones could still serve a road warrior well, especially in a quiet hotel room at night.

Although they weigh only 0.85 pounds, the PM-1s are solidly built with machined metal parts and lambskin leather coverings. The attention to detail extends to the tinniest details, such as the shiny beveled edges on the satin-finished ear yokes, which even includes a tiny edge around the headphone cable. The PM-1's overall fit and finish rival any luxury product I've seen, including automobiles and designer handbags. The inclusion of two very different and easily interchangeable cables is something that every manufacturer that makes headphones with removable cables should adopt. For travel, connected to portable devices, the shorter, lighter cable works great. At home, the longer, cloth-covered cable has the extra reach to allow for freedom of movement, at least for most folks, most of the time.

This is a good time to mention one of the PM-1's greatest strengths: comfort. They are tied in my personal pantheon of comfort with the Sennheiser HD-600 headphones. On my 7.13-hat-size head, the PM-1s are much more comfortable, especially after more than an hour of listening time, than the Audeze LCD-2 Bamboo or the AKG K-701 headphones. During the two months that I've been using the PM-1s, I have had ample opportunity to "torture test" their cable connections. The PM-1s are so comfortable that, at least 10 times (I stopped counting after a while), I got up from my desk and began to walk away, having completely forgotten that I still had the headphones on, since they weren't actively playing music. The results were predictable yet startling - after a couple of paces, the cable was yanked out, usually at the earpieces. Every time, except for the initial shock, there was no harm, no foul. The PM-1s survived multiple unintentional traumatic disconnections with no damage whatsoever to headphones or cables. That is rugged.

Headphone-PM-1-WoodBox2.pngWhile on the subject of ruggedness, I would be remiss not to comment on the overall build quality, especially at the critical stress areas. According to Oppo's product literature: "Quality control includes cross measurements for various forms of distortion and even clamping pressure. During the EVT (engineering verification test) a sample headband is stretched and its ear cups are rotated 20,000 times by machine to insure structural integrity, then twisted 5,000 times to check for environmental stresses. " Since the parts that can wear out (such as earpads and cables) are easily replaceable, for most users the PM-1s should, as long as they're not abused (such as being worn during a sandstorm), last longer than their original owners.

Another thing that will probably last longer than its owners is the PM-1's packaging. The outer cloth-covered slip case, humidor-quality lacquered presentation box, two cables, two sets of earpads, and cloth portable carrying case increase the shipping weight of the 0.85-pound earphones to over 10 pounds total. That's a whole lot of shipping costs for that big ol' deluxe package. More frugal types will be interested to learn that Oppo plans to introduce a companion model, the PM-2, for $699 without the deluxe packaging and with some of the metal parts replaced by less-expensive-to-machine plastic. Oppo claims the two headphones will sound virtually identical. Hopefully the PM-2 will be as rugged as the PM-1.

Click on over to Page 2 for the Performance, High Points, Low Points, Competition and Comparison and the Conclusion . . .

In baseball, a "utility player" must have a specific set of skills, but his principal skill must be that he is pretty good at everything, but not necessarily superstar-level at any specific skill. The PM-1 is the headphone equivalent of the best utility player I've ever had the pleasure of putting through its paces. While there is no particular sonic parameter where the PM-1 excels, when you add up all the areas where it performs at nearly reference level, you wind up with a headphone that delivers a high level of enjoyment that rarely gets in the way of the music, regardless of the device it's tethered to.

The PM-1 is a very natural- but not neutral-sounding headphone. Music has a relaxed and organic quality, but it varies from ruler-straight neutrality. This variation occurs in the treble region, where the PM-1 sounds slightly rolled off. Compared with airy-sounding headphones, such as the Stax Pro Lambdas, the PM-1 seems slightly less detailed, and the overall soundstage size is somewhat smaller than the Stax's.

Headphone neophytes often complain that headphones don't produce a three-dimensional image like speakers do. Actually, headphones do produce a three-dimensional image, but instead of being "out there" in the room, the image is "in here" inside your head. Some audiophiles never get comfortable with that. It took me a while to get accustomed to the "in-head experience"; but, once you make the adjustment, you'll find that the imaging specificity and precision that you hear with the best loudspeakers is also available through headphones. In this performance area, the Oppos are very good, but not quite as spacious, specific, and precise as the image produced by the Audeze LCD-2 or Stax headphones.

Dynamic contrast and the overall dynamic range of music through the Oppo PM-1 headphones is almost on a par with the best I've heard. This is one performance area where the PM-1s will deliver somewhat better performance when tethered to a dedicated power amplifier instead of a smartphone. When hooked up to the SicAmp headphone amplifier, the PM-1s had slightly more slam and dynamic contrast (as well as a more silent background) than when connected to my iPhone's headphone outputs.

Bass extension through the PM-1 is good; but, for those devotees of dubstep who want enough of the "sub-bass" energy to get a full dose of deep throbbing, these are not the most bass-centric headphones around. I found for my musical tastes, though, that the PM-1's bass capabilities were more than adequate. Bass definition was good enough so that the essential organic character of the acoustic bass on my own live recordings came through clearly with minimal editorialization from the Oppo in the way of bass bloat.

The upper bass and lower midrange through the Oppo are a bit more prominent than ruler-flat, giving the PM-1 a slightly warmer-than-neutral harmonic balance. Although not as warm as some, such as the V-Moda M-80, the PM-1 will augment dry, cool mixes with a bit more richness and weight. Many of the 128-Kbps Internet radio feeds I listen to sounded especially good through the PM-1s - the radio feeds' tendency toward splitchiness was reduced slightly by the PM-1's harmonic balance.

The PM-1's most seductive sonic characteristic is undoubtedly its smooth midrange. Aided in large part by extremely low amounts of intermodulation distortion, the PM-1's midrange presentation has an exemplary clarity and lack of additive coloration. While not the ultimate in extreme low-level detail resolution, the PM-1's lack of midrange distortion makes it easy to listen to individual elements within a mix. Unlike some detail-oriented headphones like the Stax Pro Lambdas, whose greater treble energy output can make some less-than-pristine sources sound worse than they really are, the PM-1 tends to "improve" inferior source material by allowing the midrange to emerge with a level of finesse that counters some of the source's sonic inadequacies. If most of your music library is made up of 320 and lower MP3 files, the PM-1 may be a better overall sonic option than a more revealing pair of headphones.

Headphone-PM-1_sideview.pngHigh Points:
• The PM-1s are efficient and easy for even a smartphone amplifier to drive successfully.
• These are among the most comfortable headphones on the planet.
• They are built to last with pre-tested pivots and yoke.

Low Points:
• Treble extension is slightly truncated.
• The PM-1s, like all open-backed headphones, do little to isolate the listener from their environment.
• The packaging is more deluxe than many prospective owners might like.

Competition & Comparison
If your headphone budget is slightly more than $1,000, you have many purchasing options besides the PM-1 headphones. If you desire more treble extension and a bigger bottom end, you should consider the Audeze LCD-2 ($995) headphones. For some audiophiles, the LCD-2's additional weight and less comfortable fit are out-pointed by their excellent sonics.

Another somewhat less-expensive headphone option is the Mr. Speakers Alpha Dog headphones. This $650 closed-ear design provides excellent isolation from external noise, as well as a very natural, articulate sound. Although not quite as comfortable or easy to drive as the PM-1, the Alpha Dogs are an excellent all-purpose headphone that delivers the best imaging I've heard from a closed-ear design.

If you have some upward stretch to your budget, the newly released Audeze LCD-X ($1,699) is another fine reference-quality headphone option. With a higher sensitivity and lower impedance than the other Audeze headphones, the LCD-X can be driven by a smartphone as easily as the PM-1.

If you are looking for the most revealing, highest resolution headphone regardless of fit or amplifier compatibility, the Oppo PM-1 will probably not make it on your short list. However, if you want easy-to-drive, ruggedly constructed headphones that are so comfortable, it's easy to forget you are even wearing them, the Oppo PM-1 may be just what the audiologist ordered. Although I had at my disposal several more revealing headphones during the review period, I often chose the Oppo PM-1s over those headphones because they are supremely comfortable and their midrange presentation is so clean and uncolored. For some audiophiles, labeling the Oppo PM-1 as "a music lover's headphone" might be the kiss of death, but I think that a large portion of audiophiles will find that the Oppo PM-1 ranks as the best all-around, general-purpose headphone currently available and can deliver more long-term musical enjoyment on a wider variety of sources and devices than the vast majority of "reference" headphones. After an hour with the Oppos, you may find, just as I did, that taking them off is the last thing on your mind.

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