OPPO's has been raising the bar with amazing product releases year after year. However, these products have been largely focused on universal Blu-ray players with performance that has gained the attention of serious home theater and audio critics. This success has allowed OPPO to pursue other components with the same meticulous passion. Two such products have recently surfaced that have been in the works for a while and have finally been officially released. The PM-1 Planar Magnetic headphones ($1099) and the HA-1 Headphone Amplifier ($1199) which are geared for audiophiles have impressive performance and build quality. We are particularly excited that we get to review both product at the same time since they complement one another.
The OPPO PM-1 Planar Magnetic headphone design has been a long time in the making. The culmination of technological breakthroughs is a result of many years of research led by a team of passionate audio and acoustics engineers, chemical and materials scientists, and audiophiles. The PM-1 planar design generates sound using a very thin and light diaphragm, whose entire surface area is evenly driven in a symmetric pull-push fashion. The use of 100% of the conductor length results in greater efficiency and high sensitivity. The magnetic system coupled with the double-sided spiraling coils on the 7-layer diaphragm allows it to generate a very stable and linear piston-like motion that ensures phase coherence and high resolution audio performance with minimal distortion. The high sensitivity (102 dB) of the PM-1 design allows them to be used with mobile devices (where output power is often limited), while still providing good listening levels.
The PM-1's sonic character can be described as effortless, dynamic, natural and engaging, all while offering a comfortable listening experience. OPPO's manufacturing process ensures that the drivers on the PM-1 are closely matched for optimum stereo imaging and soundstage. The headphones weigh 395 grams, slightly heavier than my Senheisser HD600's, but are still quite comfortable. The standard issue 1/4-inch headphone cable is detachable with each ear cup using 2.5 mm mono mini jacks allowing them to be changed. These connections into the ear cup are tight and snap nicely into place without getting loose. OPPO provided us with the (optional) balanced headphone cable featuring Ohno Continuous Casting (OCC) construction (wrapped in a black fabric sleeve) and a Neutrik XLR connector (shown). A must for the serious audiophile.
The PM-1 comes in a beautiful lacquered box, which isn't too surprising since these headphones are geared more for the high-end audiophile. Inside with the headphones are an alternative set of cloth covered velour ear pads for those who prefer them. The ear pads are mounted on rubber inserts and can be easily cleaned or replaced. This design makes switching between the leather and velour ear pads simple. The standard headphone cable is 3-meters long with a 1/4" plug. Also included is a shorter 1-meter cable with a 1/8" (3mm) plug for use with portable media devices such as iPhones, iPods, or iPads.
Denim Carrying Case
The PM-1 headphones include a Selvedge Denim Carrying Case, which is manufactured using vintage shuttle looms by a supplier for a number of boutique clothing brands based in Europe and Japan. The material is a stylish, high-end fabric that is prized for its ability to weather the elements and develop a unique aesthetic character over time. The slim design of the case is a perfect match with the PM-1’s ability to fold flat, allowing the headphones to fit easily within a backpack or briefcase. The case also protects the PM-1 from damage.
The PM-1 impedance is amazingly constant from 20Hz to 20kHz. The flat conductor pattern does not have any inductive components eliminating inductance related intermodulation distortion, which is especially common in conventional drivers with higher impedance and a large number of voice coil turns. These headphones
have a nominal impedance rating of 32 ohms with a sensitivity of 102 dB with 1 mW. This high sensitivity works great with portable media players with limited output power. Our measurements showed a nominal impedance of 31.1 ohms. There was a peak impedance of 33.1 ohms at 315Hz and a minimum of 27.6 ohms at 20kHz. The near ideal impedance of the PM-1 headphones work well with virtually all good amplifiers.
PM-1 Build Quality
The OPPO PM-1 is designed to withstand normal wear in order to guarantee exceptional performance throughout its life span. Unlike other planar magnetic headphones which are heavy, the PM-1 design is comfortable. Each earpiece pivots within the metal frame giving the user a two-axis adjustment. In addition, each side frame can be moved relative to the headband to accommodate different head sizes. The ear cushions are made out from the highest quality natural latex, which is superior and longer lasting than chemically formulated foam. It is naturally hypoallergenic, retains its mechanical spring-like properties for much longer periods, and resists moisture build up from sweating. The headband and ear pads are made of hand selected lambskin that provides a luxurious look and feel. The PM-1 planar design has impressive sensitivity numbers (102dB/mW), which is significantly higher than my Senheisser HD600 headphones (97db/W). Great headphones need to be driven with great headphone amplifiers, so OPPO didn't stop here. Instead, they introduced a high-end headphone amplifier as well.
HA-1 Headphone Amp
The OPPO HA-1 Headphone Amplifier is built around a solid and well made chassis with a beautifully refined finish. The unit features a high performance ESS 9018 Sabre32 Reference DAC built on the success of the highly regarded BDP-95 and BPD-105 audiophile universal Blu-ray Disc players. The HA-1 combines a Class A balanced headphone amplifier section with linearly regulated power supplies. The front display on the HA-1 offers a contemporary look with an easy to read 4.3-inch screen. Users can choose between an analog looking VU meters, a frequency domain (spectrum) display, or a simple status screen showing source, audio format, audio level, and volume setting. The display is used to configure the unit and can also be dimmed. Both standard 1/4" unbalanced and XLR balanced outputs are provided. Black or silver finish is available.
HA-1 Back Panel
The HA-1 has both analog and digital interfaces, accommodating virtually any source unit. Analog inputs include balanced (XLR) and unbalanced (RCA) interconnects. The digital interfaces include professional AES/EBU, coaxial, optical (toslink), and a USB DAC to interface to your computer. The USB DAC supports PCM audio with sample rates of up to 384 kHz with 32-bit resolution and DSD256 audio. The HA-1 also has a Bluetooth interface (with a high quality aptX CODEC for improved audio quality) allowing it to connect to a variety of portable devices including iPod, iPhone, iPad, and Android devices. Analog outputs are provided (balanced and unbalanced) giving the user maximum flexibility. Trigger (in/out) interfaces are also provided.
The analog outputs (both balanced and unbalanced) allow the HA-1 to operate as a preamplifier into a power amplifier or as a high-end DAC for another audio component. This versatility makes it much more than a headphone amplifier.
Inside the HA-1
The HA-1 offers some impressive design features that can only be appreciated with the cover removed. While the unit has excellent sound quality, the design topology confirms why the HA-1 achieves this level of performance. The hand-picked and paired discrete components ensure symmetry for optimal audio performance. The linear power supplies with a toroidal transformer keeps the secondary power forms as clean and quiet as possible. Linear voltage regulators provide the cleanest power generation with large bulk capacitance for plenty of energy to keep the power rails constant under the heaviest of demands. The HA-1 can generate a lot of heat with temperatures measured as high as 115 degrees Fahrenheit (46 degrees C).
The design is separated into several functions. The main controller and USB audio transport board is the brains of the HA-1 and includes the Bluetooth interface. The audio input board has the digital and analog audio interfaces. Just below this are the pre amp output buffers. The motor driven analog volume control is located just above the discrete class A power amplifier section. The ESS Sabre32 reference ES9018 DAC with input selection and gain control are centrally located on the main board. Finally, the linear power supply with the custom toroidal transformer provide the cleanest power to the high performance electronics. Protection circuits are also provided.
The remote is thin (3/8") and has a metal body with a nice feel. The remote operates from a single CR2032 3V lithium battery. Standard buttons for power, volume, mute, dimmer, and input selection are provided. There are also play/pause and next/previous track buttons that only work when using the USB DAC, Mobile USB, or Bluetooth audio inputs. The HA-1 automatically reduces the volume when switching between (normal and high) gain levels.
The PM-1 headphones are exceptionally good at revealing detail in playback material. Chesky offers some of the best two-channel recordings we have heard with 24-bit/96 kHz sample rates. Livingston Taylor's Ink DVD - Isn't She Lovely is a great example of clean acoustic guitar layered with superb vocals that have excellent resolution and fantastic dynamic range. The singer's deep vocals along with his fine acoustic guitar textures provided a great listening experience. The PM-1 provides fast and articulate bass response with a fully transparent midrange. The sounds of the acoustic strings being plucked and the harmonics were complex, but reproduced well with the PM-1 and HA-1 combo.
Another great recording (albeit 16-bit/44.1kHz) to listen to with this system is Billy Cobham's Billy's Best Hits. Track 6 - Slow Body Poppin is a wonderful recording offering his unique style of slap bass.
This OPPO PM-1/HA-1 combo was one of the more memorable reviews we have had to date. The PM-1 Planar Magnetic headphones have the ability to reveal incredible detail while being comfortable during longer listening sessions. The full sonic potential of the PM-1 headphones was made possible with OPPO's HA-1 headphone amplifier. This made for a great listening experience with plenty of high-end Class A amplification behind the high resolution music. The performance of this combo never let us down during the review period. Like many high quality playback systems, this combo has the potential of uncovering issues with poor recordings. You will likely become more critical of the content you listen to. For those on a limited budget, OPPO has also recently released the affordable PM-2 Planar Magnetic headphones ($699) offering much of the same high performance sound for significantly less money.