OPPO PM-3 Headphones Evaluation Report
It has a wide range of applications, including power production and power dispatching center, nuclear industry facility operation center, energy production center, traffic operation monitoring center, aerospace mission monitoring center, public safety mission monitoring center, financial trading center, monitoring center, radio and television monitoring center, factory central control room and many other application scenarios. These types of control rooms, Both monitoring center and control center belong to mission critical control environment, which affects the orderly operation of economy and society.Operation method, installation and maintenance of jbkz tank liquid level alarm device. The device is applicable to the monitoring and alarm of high liquid level and overfill cargo tank. Oil Tanker Cargo Oil Console,Petrochemical Ship Cargo Oil Console,Oil Tank Monitoring Console,Tank Gauge Console Monitor Taizhou Jiabo Instrument Technology Co., Ltd. , https://www.taizhoujiabo.com
First, let's briefly review the structure of the flat-panel headphones. In the HiFiMan HE-560, we talked about it. As shown in the figure, the so-called flat type comes from its physical structure and driving method. The conductive printed circuit is printed according to a certain rule, and the diaphragm is evenly placed between the two magnet plates [in the magnetic field] together with the printed circuit. The AC input signal is connected to the circuit on the diaphragm, and the diaphragm is stressed in the magnetic field. It is changed and driven. In theory, its printed circuit drives the diaphragm to vibrate evenly, just like the voice coil is flattened onto the diaphragm, and the magnetic steel is flattened into a flat magnetic pole. Of course, the principle is simple. There are many details that affect performance. For example, the two-sided magnetic poles cover the sound propagation path on the side of the human ear. The consistency and thickness of the diaphragm, and the layout, weight, and thinness of the printed circuit on the diaphragm should be considered. 
The positioning of OPPO PM-3 is relatively clear, beautiful appearance, not large size and suitable weight, low impedance and high sensitivity. OPPO hopes that PM-3 can match with a portable device. Quality headphones. Of course, it is not enough to be assured of the quality of the phone, but also launched a very sophisticated HA-2 decoder. This decoder, we will release the evaluation report in the next few weeks. In fact, the headphone plane vibration Membrane to improve sensitivity has always been the main point of breakthrough in diaphragm technology and speaker unit technology. Because the sensitivity of the previous flat-panel headphones is too low, don't say that it is necessary to mix with mobile phones and walkmans, and the amps need a lot of power. But with PM-3 positioning Similarly, there are actually HE400i/HE400s that HiFiMan has been working on. 
In the technical point of the official PM-3, a lot of features of this earphone are introduced. First, it uses a 55mm circular diaphragm, which actually makes us a little surprised, the long axis of the oval opening of the earphone ear pad. It is about 60mm. If it is a dynamic earphone, use a speaker of 50mm or more, such a cavity and volume is relatively small. Second, PM-3 uses a special process of 7-layer diaphragm, and special printing Circuit technology. Third, the use of a strong neodymium magnet as a magnetic pole. In addition, we talked about the advantages of good frequency / phase, frequency / impedance consistency brought by the plane diaphragm in the previous HE-560 evaluation. Of course, PM-3 weighs only 320 grams, and it is still very beautiful, the appearance of work is very good. Sensitivity 102dB, impedance 26 ohms, which is a very good push headphones for headphones.
Although we soon released the PM-3 headset evaluation report [time between the gallery], but we should have at least 800 hours of headset downtime, the improvement of the headset is more obvious, the sound of the headset will be soft and stretch. Less [although it doesn't seem to be new?]. When I first listened to the HA-2 decoder, I felt that its control was not good when it was big, so I decided to evaluate this headset first. Of course, today's evaluation will also be used. OPPO HA-2 as a reference source.
Corresponding to OPPO PM-3, it should be HiFiMAN's HE-400i and just released HE-400s, but we don't have these two headphones. In the evaluation, we can only use well-known dynamic headphones for reference. Considering the sound style Trends, the Sennheiser HD650 headphones will be used as the main reference in the evaluation, AKG K701, Philips SHP9000, etc. as auxiliary reference. 
Overall impression : PM-3 is a closed-design flat-panel earphone, which is different from the static design of the static earphones and HiFiMan flat-panel headphones that we have heard before. Its sound also has a distinctly closed design style. However, the blunt and fierce styles in the dynamic closed-type headphones are completely unrelated to PM-3. PM-3 is a headset with a certain flat-panel sound trend, but its sound is unexpectedly extraordinarily soft, medium-frequency and medium-high frequency performance. Very balanced, low frequency may vary greatly depending on the style of the sound source. The large dynamic performance is not good for PM-3. It is clear that PM-3 is not a HE-560 earphone at all, so it will not be carried out. Compared.
In the choice of audio source, we will use HP11, Holo Audio amps as the reference for desktop platform applications, and the fly proud X5K player as a reference for mobile players. Unfortunately, the headphone output of HA-2 decoder Control, not as good as the flying proud X5K, after the details of the difference after the evaluation.
High-frequency performance : The overall style of the PM-3 is extremely soft. It is different from the softness of the dynamic headphones. The flat diaphragm still seems to maintain a good balance, especially in the middle and high frequency parts. The sound is more stretched. And you can hardly imagine that the high frequency can be so soft under the closed structure of a moving coil earphone. However, the high frequency resolution of PM-3 is not very good, whether in X5K or With a better amp, the Sennheiser HD650 can show better high-frequency resolution than PM-3, and a certain sense of air. It also has to be dominant in dynamic [amp platform]. Of course, HD650 requires More difficult to drive than PM-3, the dynamic performance on X5K is much weaker than PM-3.
Compared with headphones such as AKG K701, the high frequency of PM-3 has a more balanced performance relative to the middle and high frequency parts, and it is softer and more detailed. However, the extension and dynamics of the higher part of the high frequency are weaker. Compared with the HD650, the PM-3 style is slightly similar, but its mid-high frequency is looser, while the HD650's mid-high frequency is more compact. But overall, this part of the sound, HD650 resolution is dominant. The advantages of PM-3 It is easy to drive, and the sound is extraordinarily soft. The relative deficiency is that the resolution is normal, the dynamic deviation, and the sound field are relatively normal. The high frequency of PM-3 is not enough to stretch, but there is no special sensation of HD650, but this is too soft. The performance of us in the AB comparison, certainly more inclined to the performance of the HD650.
IF performance : The PM-3's IF is a very big advantage. This slack IF also maintains a relatively soft, transient slow style. But it's relatively easy to drive, on X5K, even the vivo X5 Max. There is also a very full vocal performance. Compared with AKG, PM-3 has better intermediate frequency thickness and better resolution, and the volume and sound balance of the mid-low frequency interface is better. Under enough sound source [at least Better than X5K, such as Lotoo PawGold], PM-3's medium frequency is more delicate, it can easily detect the difference between it and the closed dynamic ring. Compared with the HD650, the HD650's intermediate frequency is better. The sound is more compact. We have always said that the HD650 sound is relatively rigid in the dynamic headphones, and the PM-3 is more like a slack HD650, and the IF part is slightly better. But the specific style seems difficult to describe in words. This soft, slack feeling is in a different state from the soft and slack state of the moving circle. In general, the MF of the PM-3 performs better than the HD650, K701 and other headphones under the vocal and small dynamics. Also need the support of the desktop amp. Its performance is not moving The circle is fierce, but it has a good control and sound level. But compared with the high-end headphones, it is still behind in all aspects.
Low frequency performance : We did not use Monitor 06 MX as a test platform, because its mid-low frequency taste is relatively heavy, and the driving force seems to be too fierce compared to PM-3, resulting in its low frequency feeling is somewhat too large. In X5K The HP11 and other amps have no obvious problems in this aspect. However, the low frequency performance of PM-3 is not compact enough. It is relatively unsuitable for large dynamic music under various platforms. The low frequency texture is particularly soft and the intensity is seriously insufficient. Thanks to the flat diaphragm, it seems that even so soft is not particularly confusing under the big dynamics, but there has been a slight out of control feeling similar to the closed-end headphones. However, on the three sources we chose, PM-3 The low frequency performance is basically stable. In the middle and low frequency part, the PM-3 is good. Compared with the HD650, its details are more abundant, and the mid-low frequency is more stretched. This is actually very rare in the dynamic headphones, which is also the flat earphone. One of the advantages brought by the low frequency dive, PM-3 is quite general, even with a very powerful amp, it shows a soft style. If the overall style of PM-3 is softer , then the low frequency part is to be counted It is the price paid for it.
to sum up
From the sound performance of OPPO PM-3 headphones, there is no complete grasp of the famous models such as Sennheiser HD650, AKG K701, etc. If PM-3 is a flat-panel headset with a relatively advanced positioning, then it is dynamic and resolving. The aspects are far less than the higher-grade HE-560 we have evaluated. In terms of high frequency, the dynamic headphones have certain advantages [even compared to HE-560], so compared with HD650, the high frequency of PM-3 The performance is weaker. The IF part is the strength of PM-3. If it is aimed at the performance of vocal music, then the advantage of PM-3 is more obvious. The low frequency performance is particularly picky, such as with OPPO HA-2. The low-frequency control is poor. The overall sound performance of PM-3 still has many advantages of planar diaphragm, such as relatively good balance, and relatively real transient performance [PM-3 is somewhat slow and soft, but still moving The looseness of the circle is different], calm, soft sound, medium-band and medium-low frequency partially slack state. Maybe this headset should also consider low impedance and high sensitivity, and make some compromises in tuning and performance.
If you position the PM-3 as a high-quality music listening headset, it doesn't perform well enough, and it doesn't fully show the charm of the flat-panel headphones. But in the OPPO positioning, its easy-to-drive design can be used with mobile phones. In general, it is also a very unique headset.