Oppo PM-1 planar magnetic audiophile headphones review

There seems to be much pushing and shoving in the headphone arena. Musical Fidelity and NAD have recently sent earphones and headphones out in to the wild and almost every DJ and fashionista has followed Dr Dre‘s path. Oppo have opted not to seek celeb endorsement, instead they’ve chosen to rely on quality for their Oppo PM-1 headphones. Was this a smart move?

The Oppo PM-1 are planar magnetic headphones, which use large, flat drivers rather than the contoured kind used by most headphones. One of the main benefits of planar magnetic headphones is that – like electrostatic headphones – they generally provide very low-distortion sound.

What sets these planar headphones apart from the rest (yes, there are others out there) is that Oppo claims the high sensitivity of the PM-1 with let them perform “without requiring additional amplification”.

At 395g, they’re reasonably heavy by general headphone standards but, as was pointed out, they’re not really built for joggers but for those looking for a very transparent and comfortable listening experience.

Planar speaking

Here’s the science bit. The advantages of planar magnetic technology are based on the fact that in a planar driver, sound is generated by a very thin and light diaphragm that is driven evenly over the entire radiating area.

Sound, entering your ear, has a planar wave front at the so called ear reference point (ERP), with all spectrum components in phase. A typical dynamic headphone driver, due to its phase irregularity, disrupts that. This results in less than perfect signal peak reconstruction, especially of very short impulses.

Unlike dynamic drivers that are driven from the point at which the voice coil is attached (usually near the center), planar magnetic drivers are forced to move over their entire surface. This means they don’t suffer from the modal break-up found on traditional drivers when the cone surface starts wobbling in undesirable ways at higher frequencies.

A resistive load also ensures that any amplifier will drive the headphones without any changes in spectral balance which means that you can use the PM-1 headphones even with your mobile device even without a separate headphone amp.

This headphone tech has been around since the 70s but it has been held back due to the size and weight of the magnets needed and, as cool as neodymium magnets are, they’re still heavy. The weight and size of a planar magnetic headphone driver could make wearing them a chore. Until now.

I hope that’s clear now – or, at least, clearer.

In the box

Once I had got in to the large (and heavy) cardboard box I was faced with a nicer fabric-covered box. The kind you might get if you bought an upmarket dinner set. Once the lid of the fabric-covered box is lifted the opulence of a highly polished, gloss-lacquered, dark wood presentation case with the Oppo logo inset into the case’s top panel greets you. I also dig the nice touch of an inset push-button release catch that facilitates the unlocking of this treasure chest.

Finally, inside the wood presentation case we find the PM-1 headphones plus a velour bag containing the headphones primary signal cables.

Also included is a padded selvedge denim carry case for the PM-1 which contains a set of velour ear cup pads, and a cable for mobile devices.

In total the package contains:

A fabric-covered outer box.
A lacquered wood presentation case.
A set of PM-1 headphones, which ship with a set of beautiful perforated, hand-picked lamb’s skin leather-covered natural silicon ear cup pads installed.
An alternative set of velour-covered ear pads for “longer listening sessions” or if you just prefer to have fabric against your ears.
A primary 3 metre long signal cable terminated with a 6.35mm TRS-type headphone plug.
A 1 metre long signal cable terminated with a 3.5mm mini-jack headphone plug.
selvedge denim, padded carry case for the PM-1.
A User’s Manual.

Once the gloriously shiny wooden box is opened you can see the PM-1 nestled inside the padded interior which is lined with a soft fabric. Below the cans is a small oblong box sheathed in a black fabric drawstring bag. Inside that small, oblong box sits the primary signal cables which have been specially made for the PM-1.

The whole opening sequence has obviously been designed to give the consumer a sense of occasion and I do believe that they have succeeded.

So, what’s so special about the Oppo PM-1 headphones?

The main thing that separates the PM-1 from the masses is its driver: a 7 layer planar magnetic design motivated by a FEM-optimised high energy Neodymium magnet system.

To improve performance over “average” planar magnetics, this driver utilises a spiralling pattern of flat conductors which are etched on both sides of the diaphragm, allowing twice as many conductors to be placed within the magnetic field. Oppo states that this leads to improved sensitivity, better damping, and more even application of drive force.

“The PM-1 utilizes a planar magnetic driver that sets it apart from the majority of headphones on the market. In our planar magnetic headphone, sound is generated by a very thin and light diaphragm whose entire surface area is evenly driven. The diaphragm is driven in a symmetric push-pull manner, and the magnetic system and conductor patterns have been optimized for maximum sensitivity and consistency.”

I have recently been made aware of other planar magnetic headphones available at the moment so doesn’t that stand for them as well? Not according to Oppo who states:

“Unique to the OPPO PM-1 is the use of a double-sided diaphragm, which allows us to place twice as many conductors within the magnetic field and eliminated any passive return zones where the conductors do not work. This results in the use of 100% of our conductor length, which in turn results in greater efficiency. In addition, our flat conductor pattern eliminates inductance-related intermodulation distortion, common with dynamic headphones, and the OPPO PM-1’s purely resistive impedance means that sound quality is unaffected by a Headphone amplifier’s output impedance.”

Before I, and you, get bogged down with all this tech talk it is also worth mentioning the materials and build quality of the PM-1.

I have already mentioned the hand-picked lambskin on the headband and ear pads but there is also precision machined aluminium parts. All this has been twisted and stretched in line with Oppo’s strict production tolerances, all of which should all add up to a luxurious feel that will last you years to come.

Of course, for those with a bit less to spend, Oppo did mention that they are aiming to bring another set of headphones to market, the PM-2. While the PM-2’s will boast the same driver and acoustic performance as its big brother, a £699 price tag means “materials and processes that are more suitable for quantity production”, i.e. synthetic leather and presumably a bit more plastic in place of the metal parts.

The nitty gritty

The PM-1 are a circumaural (over the ear), open backed set of headphones and therefore provide little, if any, noise isolation and will be leaky. To be honest, as a spectacle wearer, those closed designs that rely on a tight seal between skull and earpad don’t quite work due to the arms of my glasses anyway.

I am happy to see that the PM-1s use detachable cables and comes bundled with 1 meter and 3m lengths with them terminating in 3.5mm and 6.35mm stereo jacks respectively.

“The OPPO PM-1 combines high sensitivity with low weight, allowing it to be used freely with portable devices without requiring additional amplification.”

The drivers are selected in order to give an equal response and having a cable going to each side also aids with the parity of audio between sides.

First impressions

The PM-1 is remarkably sensitive and very easy to drive. In practice, this means you would choose an amplifier, if indeed you even decide you want to use one, more on the basis of sonic qualities than with an eye toward making sure your amp has ‘enough’ power (with this headphone, just about anything puts out ‘enough’ power).

When I first got ‘ears-on’ with these headphones it was through an Oppo BDP-105EUI Blu-ray player and the yet to be released HA-1 headphone amp. That’s me stood up in the grey striped jacket and pale shirt by-the-way.

Naturally the PM-1 would have to sound wonderful through all of that, especially as all of the gear is from the same company. To say that I was impressed though would be an understatement.

My initial feelings, which I tapped out in Evernote as I listened to the supplied disc, was that the PM-1’s midrange is rich and revealing, yet smooth with no apparent peaks, rough edges, or signs of overshoot or ringing. The bass is well detailed and decidedly full-bodied without being obtrusive or loose. Highs are also very smoothly dealt with.

What really struck me was the clarity of the vocals on the non-instrumental tracks. They weren’t shoved forward in the mix, nor were they overpowered by the backing. The singers appeared to have their natural stage, just enough front and centre to give them the spotlight, but in a modest and clear way.

Back home, listening to them through my Musical Fidelity V90 rig (above) and a Cambridge Audio CD player I was hoping that the PM-1 would still shine even though my disc spinner is aged and my DAC and headphone amp are not as swish as the Oppo units at the release stations.

Thankfully my fears quickly vanished on the opening of Portishead’s Glory Box. That weighty, controlled, and well-extended bass was still apparent with the mids sitting slightly forward with a warm and full natural sound which works wonders on Beth Gibbon’s vocals. The brass sections were handled with nicely controlled highs.

Slinging on Addicted to that Rush by Mr Big and snapping on the velour earpads the Instruments felt suspended in their own space rather than being pinned to the spot. Charles Mingus playing Boogie Stop Shuffle could have almost been in the room with me. The horns surrounded me and the urgency of the piano and drums had me lost in a smoky cafe. I did feel that the velour cups gave a rounder bass when comparing like-for-like with the leather ones.

Back to the leather cups and Dog Days are Over by Florence and The Machine graced my ears with an Incredibly crisp, clean and natural experience. The PM-1 carry the energy nicely with a very clean and separated sound. At this moment I realised that I didn’t have to ‘work’ at listening to the nuances of these tracks. Everything about the Oppo PM-1, from the physical construction of the headphone to its sound, is as comfortable and naturally relaxing as a sunny weekend with an empty schedule.

Considering how heavy planar magnetic headphones are said to be the comfort factor is amazing and I could see me, should my actual schedule allow, listening to album after album for hours on end.

Conclusion

When was the last time you saw some headphones bearing the Oppo logo? Usually for first-time products coming from companies this is where I’ll start off by saying something like – You have to keep in mind that X has never released a Y before… But not this time!

Even though I’ve not clocked up many hours with the PM-1 I have the distinct feeling that you’ll be reading quite a few positive reviews from more esteemed audio pundits than little ol’ me very soon.

The build quality and all-around fit and finish of these headphones alone are already enough to set them apart from most other brands. Granted, you’d expect no less for the £1100 asking price but the Oppo PM-1 are made of high-quality materials and show a great deal of craftsmanship.

With the high tech planar magnetic drivers on board and a noticeable attention to detail the PM-1 are well worth the asking price, if you can afford them.

If not, perhaps the promise of the PM-2, a pair of headphones that don’t sacrifice audio performance, but comes in at a more affordable price point of £699 would keep you interested?

Should you have the money then I’d also recommend testing out Oppo’s HA-1 headphone amplifier when it’s finally released next month and, with the PM-1, you’d have yourself a top notch personal listening rig.