“Magnets, bitch!”. Breaking Bad’s Jesse Pinkman isn’t the only one to get excited about the powers of attraction. The rise and rise of Audeze and Dan Clark’s Fostex-modifying MrSpeakers brands are indicative of planar magnetism’s pulling power.
Planar magnetic designs differ from their dynamic driver brethren. A patterned array of conductive material – often very flat copper wire – is attached to a thin membrane (the diaphragm) on either side of which sits one or more magnets. When AC current is passed through the conductive material it interacts with the magnets causing the diaphragm to vibrate. Et voila: sound!
One technical advantage of going planar magnetic is the diaphragm’s more uniform excitement (than dynamic drivers) and the subsequent lower distortion. In this reviewer’s listening experience, planar magnetics tend to serve up greater clarity, especially in the midrange, and a snappier take on rhythmic drive.
Think of it this way: I liken the benefits planar magnetic headphones to that of Magnepan loudspeakers. The Minnesota company isn’t named as such for nothing: they specialize in planar magnetic loudspeakers from which one often hears better speed and transparency than similarly priced box loudspeakers. Magnepans also tend to play better in smaller, more difficult rooms. Notching up negatives on the other side of the balance sheet are size and a more limited aesthetic appeal.
The compromise with many planar magnetic headphones is weight. Magnets pile on the pounds – just ask anyone who owns the HiFi Man HE-6 or a piece from Audeze’s LCD range.
One of my personal favourites, the Audeze LCD-X, weighs in at 612g whilst the closed back LCD-XC notches up a whopping 650g – clearly they’re not everyman headphones. Another of my daily drives is MrSpeakers’ Alpha Prime. They tip the scales at a more acceptable 440g.
Then there’s the dedicated amplification needed to do planar magnetics proper justice. The Alpha Prime’s 90db sensitivity and 50 Ohm impedance has them requiring more get-up-and-go than that provided by your average smartphone or integrated amplifier. Take a look at the Hifi Man HE-6’s sensitivity: an eye-watering 83.5db for which you’ll need some fairly serious muscle.
In soliciting the talents of Igor Levitsky, famed for his work on BG Radia’s planar magnetic loudspeakers, China’s OPPO made quite the splash in 2014 with their PM-1 (US$1099, reviewed extensively here) and PM-2 (US$699) headphones. The latter are (almost) identical to the former but with some niceties – presentation box, balanced cable and extra ear pads – and RRP height removed.
Guess what PM stands for? You guessed it: planar magnetic.
Levitsky’s work for OPPO has resulted in headphones with two significant points of difference. At 395g, the PM-1 are lighter than rival units whilst a 32 Ohm impedance coupled to 102 db sensitivity means an altogether easier drive; news well received by those who spent big on an Astell&Kern portable (or similar) but who aren’t keen on strapping on a second box for beefier amplification.
You don’t need a dedicated headphone amplifier for the PM-1/2 right away but adding one when funds allow nets appropriate performance gains. If you’re one step ahead of me here you’ll be spying the considerably sharper value of the PM-2, the savings from which could be diverted to amplification. A PM-2 + Schiit / Burson will convincingly best the PM-1 driven from an integrated amplifier’s headphone socket.
Open-back designs both, the PM-1 and 2 are for use in quieter environments where two-way isolation isn’t required.
For go anywhere deployment, a closed-back headphone is needed, for which there is an abundance of options to be had, especially around the US$500 marker: the Master & Dynamic MH40 (reviewed here), NAD’s Viso HP50 (reviewed here), and KEF’s M500 (reviewed here) are three that I’ve spent considerable time with and rate highly, each for their own reasons. There is no single ‘best’.
It is into this field that the Levitsky-designed OPPO PM-3 lands. A closed back, 26 Ohm / 102db headphone that sells for US$399 isn’t such big news until you learn that the PM-3 are planar magnetic. OPPO’s entry-level cans STAND OUT from the crowd on topology. At a little over half the cover charge of the PM-2 (US$699), could we have our cake and eat it?
I was fortunate enough to visit the OPPO factory in Guangdong last month to see/hear how things went down. The vibe at the Dongguan facility is closer to a Google campus than the more traditional manufacturing base operated by Rotel across the water in Zhuhai.
For starters, some of OPPO’s 20 000 employees (let that sink in) live on site, the majority of whom work in the mobile phone division. The other thing to strike soon after we arrived was the youthful vibe – 70% of OPPO employees are under 30 years old. Even founder and CEO Tony Chen isn’t much older than 40.
OPPO earned their reputation on manufacturing some of the world’s best Blu-ray players. In Dongguan, production of the BDP-103/5(D) is still going strong. (That’s beyond the scope of this article).
Next to the larger production lines dedicated to Blu-Ray players sits a smaller line where a run of PM-3 headphones are coming halfway to life. The headband and earshells are made in the Chinese factory before being checked, boxed and sent to the Philippines for assembly – that’s where the driver is fitted.
The PM-3 driver shares a similar structure to the PM-1. The inductor coil and ‘FEM-optimised Neodynium’ magnets sit on both sides of an OPPO-patented 7-layer diaphragm. It’s the PM-3’s driver shape and size that differ. Inside the PM-1 sits an oval-shaped driver that measures 85mm x 69mm. The PM-3’s is circular with a 55m diameter upon which the inductor material coils in an inward fashion for greater ‘consistency’.
Remember, this is a closed-back headphone. The inside of the earcup is lined with a polyester fibre that absorbs some frequencies but reflects others. Added to the voicing recipe are three tiny vent holes tucked away out of sight within the plastic ridge located on the lower half of the earcup.
Both the CNC-d aluminium ‘hanger’ headband and earcups are nicely padded and finished in PU (polyurethane) leather. What first stood out to this reviewer during flights to and from China was just how well the PM-3 isolate the listener from external noise, the upshot of which means lower SPLs for proper audible satisfaction and an associated uptick in battery life on one’s portable player.
The PM-3’s sonic personality stems from their core talents with transparency. The entry-level OPPO aren’t as warm or as meaty as the Master & Dynamic MH40 but neither are they as tardy with timing; the PM-3 are lickity split fast with rhythmic charge. If you need a headphone with an abundance of bass weight, the PM-3 aren’t it. On low end oomph you’re better served by the MH40.
Compared to the KEF M500 (which are on-ear), the PM-3 don’t present with as much boisterousness or lower-treble excitement. The OPPO midrange stands a few steps further back from the KEF. The Chinese ‘phones are more considered and refined in their approach to kicking ass with rock n roll. Where the PM-3 truly excel is with acoustic guitar-strum finesse – notable on Talk Talk’s The Colour of Spring – and tighter composure during Fela Kuti’s more furious percussive outbursts. These talents sum to a listening experience that’s equal parts exciting and relaxed. Whether to call this bipolar or balanced, I just don’t know.
The pronged arms that support each earcup is also aluminium but the end pieces upon which the channel markers and OPPO logo are printed are plastic that’s designed to look like aluminium, apparently used to minimise both production costs and weight. The PM-3 headphones enter the ring at 320g; that’s 75g lighter than the PM-1 and 65g lighter than the PM-2.
Back at the factory, a sample is taken from each production run for stress testing. A thousand stretch-and-bend cycles are applied to each pair in the sample set before the batch is approved for shipping.
On portable player matching for which the 1.2m supplied cable was deployed. The cooler, drier Sony ZX-1 moved things too far towards dessication. Its lower treble illumination and short-order bass delivery had things sounding positively dehydrated! Ultimate paydirt was struck with an original AK120 pushing bits over toslink into ALO Audio’s International+. Playing it down the middle with more-than-acceptable agreeability were the Pono Player and the AK120 II. The latter’s richer tonal balance derived from more mid-bass coupled to less treble etch proved to be a terrific fit for the PM-3.
The Astell&Kern romance doesn’t end there – did you know that these headphones will also run balanced? I didn’t…until our factory tour hosts let it slip during a post-lunch PowerPoint punch. For now at least, you’ll need to BYO cable.
Also dropped into the audience’s lap was news of planned colour variations. The PM-3 are currently available in black or white. The red, blue and green variations slated for release later this year are likely to divide opinion.
Many will spy OPPO’s triple-whammy of weight, copacetic impedance/sensitivity and affordability and take the portable audio field goal. Even the Selvedge denim carry case, that sports improved internal moulding and additional padding since its PM-2 inception, strikes just the right side of understated quality – a lot like the PM-3 themselves.
However, it’s the 3m cable (also supplied) that has the PM-3 endzone-bound. Many an integrated amplifier arrives with quarter-inch headphone socket ready to rock, one that comes up short on raw power when compared to dedicated headphone solutions from the likes of Schiit or Burson. The upshot for the listener rolling loudspeaker and headphone amplification into a single box is a pair of Sennheiser HD650 will sound thin and reedy.
Peachtree Audio’s 220SE integrated is no exception. It fails to properly nourish the HD650 for which even the palm-sized Schiit Vali hybrid does a better job. Sounding cooler, smaller but no less refined and delivering far superior top end extension, the PM-3 go where the HD650 cannot. Driven from the lesser-milliwatted Peachtree’s in-built headphone socket, the OPPO cans come alive with ease and the 3m wire takes it all the way to the couch without disturbing those sharing the room.
As one might expect the PM-3’s performance rises with the aforementioned Schiit in play. It’s good to know these headphones can turn it on with better amplification in play but can still please at the hands of the Peachtree. That’s important intel for those who wish to maximise the return on their integrated investment, whether it be a NAD, a Rotel or a Cambridge.
The conclusion extrapolates itself: here is a more affordable headphone from OPPO whose compromises with scale and macro-dynamics compared to more luxurious, open-backed models – including OPPO’s own PM-2 – is easily counterbalanced (and then some) by a go-anywhere, hook-into-anything convenience.
The PM-3 deal a price-performance ratio so keen that they could easily serve as a benchmark against which all other closed-back contenders below US$500 should be assessed. I’m not usually one for penning pull quotes. I’ll go the long way ‘round to avoid writing sensationalist phrases that could be lifted by manufacturers for promotional purposes, but seriously, at the very least, do yourself a favour, take some time to audition the OPPO PM-3 before you buy anything else.
Further information: OPPO Digital