Oppo Digital • PM-1 Headphones

by John Crossett | March 10, 2015


When I was a teenager in the late 1960s, there were only two things every guy my age had to own -- a car and a stereo (not necessarily in that order). We all wanted a car so we could get around (and hustle chicks) and a stereo because that was how we listened to the music that was so important to us, and because we spent much of that listening time with our friends, sharing and discussing our experiences (while still trying to hustle chicks).

But the past decade -- and slowly over the decades leading up to it -- has seen a paradigm shift in the way most people listen to music. The stereo has been replaced -- first by multichannel home theater, which never really took off as a medium for listening to music, and then by personal listening devices and headphones, which very much have taken off. Both of these methods of listening have taken us further away from human interaction and really listening to the music. Today, personal listening constitutes the fastest-growing segment of the audio market, with all kinds of headphones, earphones, headphone amps, and listening devices proliferating and selling at rates most audio companies would kill to have. Oppo, which started making high-quality DVD and, later, Blu-ray players for the discerning audiophile and videophile on a budget, has now expanded their lineup with a high-end headphone amp, the HA-1 -- and the subject of this review, the PM-1 planar-magnetic headphones, which sell for a not-insignificant $1099.

But the first question we should be asking is: What is the major objective of a pair of high-quality headphones? I believe it should be the same as a pair of good loudspeakers: the faithful reproduction of the original recorded signal, with as little editorializing of its own as possible. Now, perfect reproduction is a wonderful goal to strive for, but as we all know, it’s one we’ll never reach. But that doesn’t mean a designer should not attempt to come as close to the impossible as possible. One thing that gives headphone designers a distinct advantage over speaker designers is that they don’t have to take room acoustics into account. That leaves them freer to concentrate their efforts on the faithful reproduction of whatever signal is fed to the headphones.

Different headphone technologies -- whether dynamic cone, electrostatic, or, in this case, planar magnetic -- have different sonic signatures, just as their speaker cousins do. The drivers of planar-magnetic designs like the PM-1s have just a thin diaphragm that’s easier to drive more evenly than a dynamic cone. In the PM-1, Oppo doubles up on the conductors -- there’s a set for each side of the diaphragm -- to allow more of the surface to be driven. This lets the PM-1s squeeze out even more phase-coherent sound with greater resolution and lower distortion, thanks to the drivers’ lighter weight and shorter, more linear pistonic action. One of the side benefits is that the PM-1s’ impedance of 32 ohms is low enough to make amplifier matching less of a problem.

The PM-1s’ appearance, too, differentiates them from their competition. While other planar-magnetic over-the-ear headphones I’ve reviewed have larger, round earcups, the PM-1s’ oval/rectangular earcups fit over the ears slightly better while weighing less. I found the PM-1s to be by far the lightest, most comfortable planar headphones I’ve tried. You get two different sets of earpads to use, depending on your preference and/or the weather: lambskin or velour. I loved the feel of the leather, even in the hottest weather, so I was disinclined to use velour pads -- although they, too, are comfortable; it’s nice of Oppo to give the user a choice. The earcups rotate sideways, allowing the PM-1s to be easily slid into the denim storage bag Oppo provides, along with a beautiful wooden case.

Oppo also includes two different types and lengths of cable. The main cable is about 10’ long, made of OCC copper, and is terminated with a typical 1/4" plug. It’s sheathed in black fabric that adds nothing to the sound passed through it, even if it rubs against something -- one less thing to worry about. The other cable is maybe 3’ long and terminated with a 1/8" mini plug for use with portable devices. Both cables attach to the PM-1s with left and right miniplugs, so swapping is a breeze. If you wish, XLR-terminated cables can be purchased directly from Oppo in lengths of 2 ($129) or 3 ($149) meters.

I used the Oppo PM-1s with both my Master Electronic Original headphone amp and my HeadRoom Micro amp with DAC. Other headphones were my reference AKG K-701s, as well as my notes on and sonic memories of the Audeze LCD-2 and HiFiMAN HE-500 headphones, which I’ve  reviewed. The sources were digital: either my Pioneer DV-79AVi universal player or iPod Classic. For fun, I plugged that 1/8" miniplug directly into my iPhone 6, with results good enough to tell me I could do this in a pinch and enjoy what I heard -- the Oppos weren’t in the least fazed.

I began listening with one of my favorite SACDs of acoustic music, the eponymous first album by Tiny Island [Opus 3 19824]. I treasure this disc for its wonderful instrumental music as well as for the plethora of acoustic instruments used, which give me a more exact reference with which to judge whether the piece of gear under review is getting the tone and timbre of the instruments right. Through the PM-1s, the overall sound of Tiny Island was never forced or thrust at my ears; instead, I heard a relaxed presentation that seemed to draw me further and further into the music. Plus, the microdetails that help make reproduced music sound less canned and more real were brought to the fore. For instance, when listening to the maracas, I could hear the beans rolling around in the hollow body as separate entities, each making a distinct sound that could be easily distinguished within the soundfield. Tiny Island also demonstrated that, unlike many planar designs, the PM-1s could reproduce bass. Not earth-shattering, deep-as-Grand Canyon bass, but good, solid, deep, well-defined bass that laid a proper foundation for the music played over it. As I went on to listen to other discs, this phenomenon did not diminish in the slightest.

The PM-1s’ lightweight, quick-moving diaphragms really showed their strengths with dynamic music. For instance, the opening of "Mississippi Queen," the first track of Mountain’s Climbing! CD [Columbia/Legacy CK 86577], features drummer Corky Laing banging away on a cowbell. The PM-1s gave the full feel of stick striking brass, from the opening transient to the last decay of each rap. Even when guitarist Leslie West comes crashing into the song, the Oppos didn’t flinch. They simply reproduced all the power of his chords, with no loss of dynamics. Nor did power -- amplifier power, that is -- cause the PM-1s to even raise an eyebrow. Climbing! just begs to be played loud, and the PM-1s showed that they could keep their composure no matter where I set the volume.

Reproducing voices is a strength of planar speakers and planar-magnetic headphones, and it was for the PM-1s in particular. The Oppos could reproduce voices with extreme realism. With the title track of my friend Eric Hanke’s latest recording, Factory Man (a one-off 24-bit/96kHz DVD-A burn of the album [Ten Foot Texan Records TFT00102]), the PM-1s accurately reproduced the slight nasal quality of Eric’s voice, while retaining the sense of air coming up past his vocal cords and through his mouth as he formed each word. Women’s voices, from Eva Cassidy’s to Alison Krauss’s, were rendered with the purity and realism both singers display and deserve.

The Oppo PM-1s easily conveyed the sense of space from concert venues and the fine touches of various kinds of music. I realized this while listening to Herb Ellis and Joe Pass’s Seven, Come Eleven SACD [Concord Jazz SACD 1015-6]. That this set was recorded outdoors was clearly obvious -- from the first introduction, I got the feeling of voices and notes wafting off into the air. This didn’t keep the PM-1s from differentiating between Ellis’s and Pass’s guitars. Ellis’s lighter, quicker fingering was in stark contrast to Pass’s deeper, fuller picking, and the PM-1s didn’t skip a beat in detailing that difference. The great Ray Brown’s double bass was full, woody, and deep enough to come across as real.

Like most planar headphones and speakers, the Oppo PM1s fell short of perfection by not reproducing bass as deeply or as powerfully as many dynamic headphones. Sure, the PM-1s’ bass was deep enough for most music, and very well defined, but if you like the depths fully plumbed, these won’t do it. The only other nit I might pick is that, as well built and good-looking as the PM-1s are, they may not strike everyone that way -- if, after hearing them, one could call that a weakness.

I compared the Oppo PM-1s with both my personal reference headphones, the AKG K-701s ($499), and my aural memories of the Audeze LCD-2 ($995) and HiFiMAN HE-500 ($699) planar-magnetic headphones. I’ll get the aural memories out of the way first, as they’re the least reliable. My listening notes remind me that the Audezes were more detailed, the HiFiMANs more naturally musical. The PM-1s seemed to split the difference, offering enough detail to make the music I listened to sound real, with a relaxed, unhurried performance that allowed me to listen for hours on end without fatigue.

Stacked up against my AKG K-701s, the Oppos had the same ease of presentation, but with a different sonic texture -- a more laid-back, smoother, even presentation, that drew me into the music, as opposed to the more forceful presentation AKGs. The PM-1s went deeper in the bass, but bass has always been the AKGs’ weak point, despite their detailed sonic signature. There was an evenness to the PM-1s’ sound that the K-701s couldn’t quite match. Up top, the AKGs seemed to require a bit less effort to reach the highest highs than did the PM-1s, though it was close.

If the price were the same, it would be the Oppo in a cakewalk. But price isn’t dismissed that easily -- if dollars matter, listen to both. If cost isn’t much of an object, grab the Oppo PM-1s and never look back. I don’t think you’ll be seeing (or hearing) anything gaining on you soon.

Do the PM-1 planar-magnetic headphones live up to Oppo's hard-won reputation? They do. They live up to their planar heritage with a detailed and natural presentation, and they offer good looks and intelligent design. If you’re looking for planar-magnetic headphones, or headphones in general, should you make a final decision without having heard the PM-1s? Absolutely not. Toss in the fact that they’re easy to drive -- I could drive them straight from my iPhone with good results -- and they make your choice of amplifier less important, although the better the amp you use, the more the PM-1s will reveal in your music.

The Oppos offer stiff competition to other planar-magnetic headphones I’ve heard, such as Audeze’s LCD-2s and HiFiMAN HE-500s, and in some ways surpass those two planar icons. The PM-1s are definitely the lightest and most comfortable of the three, and with a sonic signature that offers enough of a contrast to either, the Oppos should be on your list of must-listens before you lay down money on a pair of high-quality ’phones.

Once again, Oppo has shown that when they enter a field, they don’t come just to play, but to lead. In the field of planar-magnetic headphones, they’ve started off right near the top. The PM-1s are one of the finest headphones of any technology I’ve heard.

Price: $1099.
Warranty: Three years parts and labor.

Oppo Digital, Inc.
2629 Terminal Blvd, Ste B
Mountain View, CA 94043
(650) 961-1118

More on the PM-1s

Before even one note comes from their earpieces, the Oppo PM-1s draw attention. They are one of the most stylish headphones on the market, looking both classic and contemporary with their combination of black-and-silver earpieces and lambskin earpads and headband. If Gucci made headphones, they might look a lot like the PM-1s. Once on your head, they almost float, gently resting instead of grabbing and squeezing. They are undoubtedly one of the most comfortable headphones on the market today, lending themselves to long, comfortable listening sessions.

They are sonic winners too, offering the coherence and midrange purity expected from planar 'phones, along with sufficient high-frequency air and bass grunt. Their sound is on the smooth, silky, ethereal side of the equation, more so than the planar Audeze LCD-3s, which are the costliest headphones I've heard. Well-recorded music of all kinds sounds extraordinarily lithe and lively with the PM-1s, and jazz especially opens up.

I've expressed my issues with Blue Note's many RVG CD reissues, because as a group they sound overly lean and voiced toward the treble. They can sound downright nasty with unforgiving components, but not so with the PM-1s. I wouldn't summarize the sound of these 'phones as euphonic -- as in grossly colored -- but rather graceful, more about touch and texture than ultimate sparkle and punch. The PM-1s won't have you thinking that they challenge the bass weight and power of the Sennheiser HD 650s, for instance, whose balance will seem bass heavy to some listeners, especially those who hear the PM-1s immediately before. Like the rest of their presentation, the PM-1s' low frequencies are naturally rendered, not excessive, and they are integrated well with the rest of the sonic spectrum, underscoring the coherence of the planar-magnetic technology in general and the PM-1s in particular.

Overall, the Oppo PM-1s are among the very best headphones I've heard and easily the most comfortable. If you want high style and refined sound from your personal listening rig, Oppo has succeeded as well with the PM-1s as with any of their DVD or Blu-ray players.

-Marc Mickelson

Associated Equipment

Digital sources: Apple iPhone 6, Pioneer Elite DV-79AVi universal disc player.

Preamplifiers: Audio Research LS17SE.

Headphones: AKG K-701.

Headphone amps: Master Electronics Original, HeadRoom Portable Micro with DAC.