Portable Luxury at a Lower Price: The Oppo PM-2 Measurements

Click on graphs image to download .pdf for closer inspection.

The graphs above are for the stock PM-2 with synthetic leather pads. All commentary in this measurement section will be regarding the above graphs for the PM-2 as shipped. Graphs for the PM-1 and PM-2 with all pads can be found by clicking the links below:

Raw frequency response plots of the PM-2 with stock pads shows a headphone relatively immune to changes in frequency response with headphone movement. Slight changes below 30Hz should be fairly inaudible. However, some significant changes occur between 3kHz and 12kHz to me indicating that breaking the seal on the ear pad might be spoiling the Q of the acoustic volume between the driver and the ear. One enthusiast has noted that adjusting the clamping pressure to be very light improves treble response and imaging. I suspect this is again a case of spoiling the Q of the resonance and allowing cleaner response in this region.

Compensated frequency response shows a very flat headphone from 20Hz to ~1.5kHz. My preference would be a slight (2-3dB) bass boost below 120Hz. I like that the response is fairly flat between 1kHz and 2kHz as this area is important for giving a sense of presence to vocals. Other than the peak at 9kHz, the treble response rolls-off fairly quickly after 2kHz and remains about 5dB lower than ideal.

30Hz square wave has excellent shape and coupled with the low bass distortion seen in the THD plot verifies the excellent quality of bass response heard in listening.

30Hz square wave shows an initial leading edge spike of about the right size, but having some modest subsequent ringing. This is where the artificial sound heard in listening tests may make its appearance. I think it's worth drawing your attention to the PM-2 with PM-1 original leather pad measurements where we can see less of this ringing while retaining a nice clean impulse response. The PM-1 leather pad was my preference with the PM-2.

THD+noise plots show a similar mid-range bump in distortion as the PM-1, but with the PM-2 damping changes the distortion appears to be slightly higher in level. I did hear the PM-2 as slightly more confused sounding than the PM-1 on complex music. Otherwise, bass and treble distortion are fairly low, and good separation between the 90dB and 100dB line show good power handling at the extremes.

Impedance a phase plots show a 33 Ohm headphone with one bump at 300Hz. The Oppo PM-1 has two bumps in this neighborhood. I suspect the change in damping behind the driver accounts for this difference.

Isolation plot shows some modest isolation above 2kHz; it's somewhat unusual for an open headphone. With 58mVrms needed to achieve 90dBspl in the headphones, the PM-2 is substantially more efficient than most planar magnetics and will be driven to solid levels by portable devices.

I see these measurements as marginally worse than the PM-1. With the PM-1 leather pad measurements are slightly better, and to my ears the PM-1 with Alt pads and PM-2 with PM-1 leather pads are very comparable.

Oppo Digital
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Za Warudo's picture

I'm fine with that, but I think a lot of dedicated readers who own them as well as people are interested in the new planar magnetics are very interested in a review of the new Hifimans. Plus, you've reviewed other headphones that didn't meet your personal tastes like the P7, SRH1540, and the Q701.

Sound Maniac 13's picture

PM2 OR Fidelio X2?
I know that the X2 has more bass and it is not comparable to PM2.
I only can afford one of them, so PM2 OR X2?

Thank you :)

Tyll Hertsens's picture
I liked those cans you mentioned for their very articulate and controlled treble, even though it was elevated above my liking. I didn't like the way the new HiFiMAN headphones responded in the treble...but I acknowledge it might be within bounds for others. I simply see no good reason (except for the good page view numbers a popular headphone would garner...and that's a bias I'd prefer to leave out of this equation) to produce a negative review for a product that quite a few others seem to like.

veggieboy2001's picture

You mentioned the HE560 in your article, but I wasn't sure if you had a chance to hear the 400i...I thought the treble to be very well done to my (less experienced) ears.

AsSiMiLaTeD's picture

Tyll, what are your thoughts on the Oppo cans compared to the Philips X1?

ManiaC's picture

Tyll, what are your thoughts on the Oppo cans compared to the Philips X1?


Tyll Hertsens's picture
X1 is a basshed can. The Oppo isn't. No comparison really. I've got the X2 in the house, and will be reviewing it soon.
AsSiMiLaTeD's picture

Can you give us a quick one line sneak peak on the new X2 vs the X1?

Chrisknos's picture

Will you be boasting about the removable pads in the X2's?

ManiaC's picture

Thank you Tyll

tony's picture

There you have it , LCD2 performance at the low power level , an entire Audiophile grade music system that fits in a glove box , look how far it's all come , in our lifetime !!
The Harvey guy can say that we've already got there with his IEMs but who wants to go-in for Ear Molds and not sharing ?
Still , the Shure Universals or EtyMotic Universals all use those tiny Pico amps to good result .
Today , a thousand bucks goes way-far into outstanding !!
Used to need $2k or $3K to get a start on a good pre-amp , a baby Wilson system will crush $50k of spare slush fund cash commitments to create a foundation for a decent system , a lot of money for bite-bar imaging and lease breaking sound levels , not to mention the Spousal accommodations in way of relationship Capitol expenditures ( shopping trips to Gay Paris and Hermes Silk Scarves , etc … )
We all seem well adjusted to iPhone sized electronics , something like an ODac or other JDS Labs combo package or any of that cutie Pico stuff or lots of other little electronics could suffice , if stolen or broken they represent only a small loss . Blow a Woofer on your Wilson with an Amp Problem and you're in for a bill like the front brake job on a Ferrari .
These Oppo 1s or 2s take plenty of pressure off anyone trying to get a good start in Headphone Audio .
Thank You for taking the time and effort to show this stuff to us , what would we do without your clarity ?
Tony in Michigan

TMRaven's picture

What makes you like the HD800 so much despite its extreme brighntess that you can't give a review for the HE-560 or 400i Tyll? Have you grown incredibly sensitive to treble in the recent months? Seems like only headphones with 10db shelves after 1-2khz are automatic wall-of-famers for you these days.

Claritas's picture

It's misleading to call it portable in the title as it offers almost no isolation. "Portable" might be how Oppo wants to sell it--and it can be driven very easily but scales very little--but you can't take this thing anywhere unless you want to go deaf from cranking up the volume. Very useful review otherwise. Thanks.

Tyll Hertsens's picture
I think you're right. Probably didn't strike the right balance there.
Impulse's picture

I think transportable might be the more accurate description, easy to carry around (like for use at a hotel etc) but not something really portable in the typically defined sense (good for use while out and about, in public places).

CarterB's picture

Thanks for the review--I can imagine your frustration doing all those swaps. Do you think the OCC cable made much of a difference with the PM-2?

lukeap69's picture

That's a good question. I want to know too.

Limp's picture

There's a ~6dB difference between left and right channel at ~9kHz on all your PM-1/2 graphs. I also noticed a similar discrepancy in your latest Sennheiser review.
Has your measurement system developed a quirk?
Good write-up none the less. Seems like the PM-2 might be the reference home listening headphone I've been looking for.

Tyll Hertsens's picture
I don't think so, but not sure. FWIW the AP is going home for a refresh and recalibration sometime next week. Won't be taking any measurements until the end of Oct. That 9kHz blip is really sensitive to ear pad position sometimes. Dunno, sorry.

And I wouldn't consider them reference as much as a really pleasant listen.

Limp's picture

That's plenty reference-y enough for me :)

I guess the human input is the most likely weak point, here as most place else.
But it is consistently the right channel that receives the cut, so it might still be systematic, even if it's human.

orel1994's picture

Hey Tyll, will you ever review the HD700?

Tyll Hertsens's picture
Way too uncontrolled in the treble.
orel1994's picture

I read that HD800's anax mod can be used on the 700 to tame the treble

Seth195208's picture

In fact, the distortion is so astonishingly low everywhere else on the Oppo, that the THD peak at 300hz "looks" much worse than it actually is, in comparison.