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Author Topic: Oppo PM-2  (Read 12046 times)

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Oppo PM-2 Review and Measurements
« Reply #30 on: August 14, 2014, 12:21:39 PM »

Big thanks to OJ for selling these to me at a great price when he could have gotten more from other locations! I hope to someday meet him in person and buy him a beer.  :)p5 I've been looking forward to trying the PM-2, perhaps too much, after my experience with the PM-1. I found a lot to like about the PM-1, personally. I loved how laid-back and natural it sounded. Very relaxing and easy to sink into the music effortlessly. Unfortunately, it didn't have quite enough treble or overall detail for me, and the price simply didn't make sense. When I heard the PM-2 would be priced around $700 and later found out about the new pads that seemed to be getting some good feedback, I thought Oppo might have finally nailed it. Did they? Keep reading to find out (or, you know, don't, and wonder forever).

You can read my original PM-1 review and check out my initial set of measurements here: http://www.changstar.com/index.php/topic,1590.msg43635.html#msg43635

Do note that I later revised my compensation curve (my current and "final" version) and posted some updated results here (use these for comparisons): http://www.changstar.com/index.php/topic,1590.msg44503.html#msg44503

Also, don't trust those harmonic distortion measurements on the PM-1 measurements. At the time, I thought ARTA was exporting distortion numbers incorrectly, but, being the dumbass I am, recently realized it was simply exporting them in a different way than I thought it was. Oops! Part of the learning experience, I guess, but I feel I am on rather solid ground now with my measurements. The distortion measurements for the PM-2 should match what I saw in ARTA!

Looks, Comfort, and Presentation

Anyone familiar with the PM-1 won't be surprised by what they get with the PM-2. Despite substituting out the metal for plastic and leather for pleather, I think you'd find it difficult to tell the difference unless, maybe, you had them side by side and/or were tapping them with your fingers. I like the style and looks. Comfort is OK, but they get heavy on top of the head within an hour or two. They seem like they might be lighter than the PM-1. Not bad overall. I might have posted more thoughts in my PM-1 review, and they'd apply here.

Presentation on the PM-2 isn't quite as great as with the PM-1. No wood boxes this time around, sadly. Instead, they come with a fabric, almost denim-like, carrying case. It's a bit small and fits them snugly, but it works and is pretty nice in the end, I guess. It's definitely more practical than a wooden box, but not nearly as pretty.

Sound

I've spent a lot of time lately with headphones like the HD600 (with some extra front and back damping) and the HE-500, and any comparisons I make with the PM-1 will be entirely based on memory. Immediately on the PM-2, I noticed a balance that seemed more in line with the HE-500 or HD600. In other words, the balance seems more neutral on the PM-2 out of the box than the PM-1. Balance up until ~2KHz or so seems to be pretty good. Bass has good extension and decent detail (not too muddy or bloated), but, much like the PM-1, doesn't have a ton of balls. You might almost mistake this for rolled-off bass, like I did originally with the PM-1, but I think it's just other subjective elements at play outside of pure frequency response that are influencing what I am hearing. Or maybe my ears suck. Couple the subjective bass characteristics with the treble performance and laid-back nature, which I'll talk more about later, the PM-2 is still a bi t light-footed, ethereal, and...yes, a tiny bit limp-dick sounding (I know you were all waiting for it), but only noticeable if you compare it to similarly balanced/neutral-ish headphones that have subjectively bigger, more dangerous testicles. Sometimes I wish the PM-2 was simply more powerful sounding, though not necessarily brighter.

The PM-1 and PM-2 both share a certain lack of clarity, or, perhaps, a slightly grey vs. perfectly black sound. Slightly hazy. Don't get me wrong, as it is slight, and I noticed it seemed to vary from amp to amp. Could this be due to the slightly warm overall response? The depressed areas in the upper mids and treble? The harmonic distortion bump around 300-400Hz? I'm not sure exactly, but I'd imagine all of these play a role and, much like the bass performance, some of it is probably due to elements not captured by my measurements.

Despite what I just said, they are fairly fast and clean sounding in most areas and do an admirable job at resolving details given their relatively laid-back nature. Though, compared to the best headphones in this area, resolving abilities are probably just adequate for the price range. For some, this might be a big deal, but I'm less concerned about it.

I am very happy to report that these are not nearly as constricting or over-damped sounding as the PM-1, though it is still there to an extent. At the very least, you can visualize instruments and such to the front left and front right in the listening space, where as the PM-1 sounded like everything was wrapped directly over your ears.

Now, where the PM-2 was close to perfect for me but lacked detail and life, the PM-2 sometimes goes too far in attempting to correct these issues. After extended listening, it became apparent that the PM-2 has a somewhat raspy, rough, and edgy nature while still sounding a bit dark, laid-back, and yet neutral-ish. This seems contradictory, but I suspect it's entirely due to the narrow 8KHz peak relative to the surrounding areas. While different music and amps affect this somewhat, I found it apparent on about everything. While I don't think most will find it to be an issue, as it's not as if the peak extends above the average response, I find things like this to be horribly annoying and grating on my ears after time (or immediately).

In a sense, I think Oppo rushed the PM-2 and these new pads. I believe they could have and should have done better with a longer R&D period, and it would have been worth the wait. While the PM-2 improves on many areas over the PM-1, it lacks the same sort of finesse and cohesive sound. Too rough and raspy. The PM-1 bored me over time. The PM-2 annoys me over time, which is a much greater sin to my ears. Aside from this particularly troublesome treble area, I found the the PM-2 to retain many of the nice, smooth characteristics of the PM-1.

So, how do I feel about it overall? Equally mixed feelings trending towards positive over the PM-1. The PM-1 and PM-2 have both been "close, but not quite" headphones for me, and for opposite reasons at times. But, of course, I'm sure many of you have found me to have particular tastes and sensitive hearing in most regards. In which case, you're also probably aware I rarely stop at the stock headphone. I'm currently listening to the PM-2 with a basic front damping mod. This makes the overall tilt a bit darker up till around the 4KHz point and basically obliterates the 8KHz peak while retaining most of the other measurement characteristics above 4KHz. I've found it difficult in my early experiments to fix the treble problems without making them sound a touch too veiled overall, but if you are at all like me with tastes and hearing, you'll probably find this to be a vast improvement overall and a worthy compromise. I suspect most others will simply find it too veiled up top with my current tweak, but it remains to be seen if I can go further with internal mods. I will report more on this later. If you have any modding ideas to share with me, please let me know!

Measurements

As mentioned above, I believe I have fixed my idiocy (well, a small part of it), and the harmonic distortion results should match what I see in ARTA here. Measurements are attached as follows:

1. General frequency response
2. Left channel FR with harmonic distortion
3. Right, FR + HD
4. Left CSD
5. Right CSD
6. 4 "raw" measurements used to get left channel FR average, 2 taken from each ear
7. Right "Raw" measurements

The frequency response results do seem to indicate the PM-2 has less of a dark tilt than the PM-1, at least up until 2-3KHz or so. Fairly smooth. The large dip around 5KHz may be accurate, or it may be measurements taken from my right ear skewing the results. Hard to say, as they do have slight differences in shape and size, and I have an easier time penetrating my ear holes on the left ear with my dild...my in-ear mic doo-dad.  :)p8  You can see in the raw measurements that the latter two of each channel show this dip, and those are from my right ear. Channel matching is good.

Regardless of that, the PM-2 has a clearly less even treble response than the PM-1. The 8KHz peak is narrower than the PM-1's 10KHz peak, less depressed relative to the rest of the response, and simply has a subjectively nastier characteristic and sound to it than a 10KHz peak (edgy/raspy/annoying vs. mostly a sense of extra detail).

Harmonic distortion looks good, though we again see the spike around 300-400Hz (roughly 3% THD). I don't think this is too problematic subjectively. D2 overall seems to average around 0.4-0.5% THD, if I calculated that correctly, though this could be a limitation of my setup (i.e. PM-2 might actually be or probably is better than this). I also made some recent audio device setting changes to how I take measurements in ARTA, and it might show D2 as a bit higher than before (still quite close, and same look overall). Anyway, aside from that spike, nothing to worry about in terms of harmonic distortion on the PM-2. It's up there with other good orthos and such.

CSDs are pretty clean. Not the best. I think the PM-1 was better, if not just slightly. Not worth worrying about either way.

Raw measurements show that the PM-2 is quite insensitive to placement and fit, which I think is a good thing. Again, my two ears sometimes produce different results like this, and it is evident here. That's why I average them in the end. I've posted details in other threads about how I do measurements, if you aren't familiar with my methods.

Conclusion, For Now

Since I seem to be pretty particular with my tastes and sensitivities, I bet most people wouldn't have much of an issue with the PM-2's treble like I do. And if that is the case, I think most will find the PM-2 to improve on the PM-1 in most ways: better balance, less suffocating, more air and detail, and so on. I still think it's a bit overpriced at $700 for the sound you get, but really pretty good overall. I'm just hesitant to say I like it a whole lot, much like the PM-1. Hmm.

If you are like me and have whiny, sensitive, baby ears, I suggest you keep tabs on my future PM-2 posts. Within the next day or two, I should have some early results on a front-damping configuration I've settled with for now. Later, I want to experiment with internal damping and mods to see if I can take the PM-2 even further. Edit: Also going to look into possible pad mods.
« Last Edit: August 14, 2014, 04:59:09 PM by hans030390 »
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Hands

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Quick Mod Teaser
« Reply #31 on: August 14, 2014, 12:29:05 PM »

This isn't the exact front damping mod config I've been listening to, but this is a sort of teaser as to what I'm currently getting from the PM-2. LCD-2, is that you? File name might be a hint what I tried here, haha. Still have some testing and listening to do on what I've got now, and if I end up liking it enough for what it is, I'll post full measurements. Again, this is only front damping mods, and super simple and reversible at that. I will eventually open the PM-2 and take a look there. (Do you think THD looks more accurate here or previously from my first, early PM-2 measurements posted, taking into account differences from the mod? This particular setting uses some mic sensitivity option that will spit out ARTA graphs at the ~90dB @ 1KHz I roughly calibrate at. I can always go back, but results are close either way.)

All four pads on a PM-2. Haven't done any listening yet.
Isn't this a cardinal sin, to measure before listening?  walk the plank     :P

EDIT/UPDATE: One thing I noticed was how the sound got a bit airier and more detailed if I slightly lifted the PM-2 off my ears, just a tiny bit. So, I decided to try reducing the clamp by stretching them out. I think I hear a positive difference, but what do measurements say? Attached those, and that is with my most recent tweak config.

I also noticed these stay in place rather well if you angle the cups, so you get less of a seal in the back. Does some interesting things to the soundstage for sure. Attached measurements of that as well. All were done rather quickly, but the PM-2 behaves well and is consistent in measurements. Good enough for now. Perhaps all I needed was a slight tweak and a lesser clamp! I know it seems like it might be a small thing, but this might have taken them up a notch...very good.
« Last Edit: August 14, 2014, 02:22:33 PM by hans030390 »
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Marvey

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Re: Oppo PM-2
« Reply #32 on: August 14, 2014, 03:36:03 PM »

One thing you can try is to jam a small shim(s) between the pads and baffle, a la Jerg pads. Takes away sub/low bass a few db, but adds more air and openness.

Yes, I heard the "softness" or what I assume you are referring to as "limp-dick" as well on portables, O2, etc. The more powerful "impactful" sounding amps like the Mjolnir and 4-45 did have a Viagra affect on the PM-2.

I didn't have any issues with the treble, at least not with the Alternate PM-1 pads.
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Re: Oppo PM-2
« Reply #33 on: August 14, 2014, 04:13:44 PM »

I was considering that. I'll see what I can do with this unique pad and mounting system. Amps do indeed help it sound more powerful. Like I said, I doubt most others would have issues with the treble. I've found I've just very, very picky and am easily annoyed with stuff like this. Seems I have become more and more sensitive over the years, which is odd.
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Re: Oppo PM-2
« Reply #34 on: August 14, 2014, 05:40:15 PM »

Pretty good review Hans, most of the points are quite correct.
   One thing that stood out for me was your saying that treble spike is in level with overall FR while according to my measurements it is at least 3db higher and therefore combined with a dip right before it they do sound edgy, raspy, rough, whatever you prefer but I call it dirty treble. The immediate roll off after that spike only adds up to the feeling of treble sounding inadequately cheap. All of that was kind of veiled in PM-1 but PM-2 tuning just made it more apparent. As for their bass quality and extension I agree, balls need to grow and to me they are light footed by quite a bit and distortion spike does play a role there.
    As for rushing PM-2 production, I feel with the sound they did all they could, meaning time just wasn't that much of a factor as they had more then half a year to tune. It took you what, couple of days of listening to come up with some mods and I can only imagine what you could do in a half a year using all of their test gear.
   Overall in my opinion both PM-1 and PM-2 have different sets of flaws that keep them from playing in the first league and that's a shame because I know, they could.
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Re: Oppo PM-2
« Reply #35 on: August 14, 2014, 11:16:02 PM »

I didn't have any issues with the treble, at least not with the Alternate PM-1 pads.

His impressions sound like the original PM2 pads we heard at the Bay area meet.  Annoying treble with disjointed overall signature. 
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Re: Oppo PM-2
« Reply #36 on: August 15, 2014, 07:19:34 AM »

Pretty good review Hans, most of the points are quite correct.
   One thing that stood out for me was your saying that treble spike is in level with overall FR while according to my measurements it is at least 3db higher and therefore combined with a dip right before it they do sound edgy, raspy, rough, whatever you prefer but I call it dirty treble. The immediate roll off after that spike only adds up to the feeling of treble sounding inadequately cheap. All of that was kind of veiled in PM-1 but PM-2 tuning just made it more apparent. As for their bass quality and extension I agree, balls need to grow and to me they are light footed by quite a bit and distortion spike does play a role there.
    As for rushing PM-2 production, I feel with the sound they did all they could, meaning time just wasn't that much of a factor as they had more then half a year to tune. It took you what, couple of days of listening to come up with some mods and I can only imagine what you could do in a half a year using all of their test gear.
   Overall in my opinion both PM-1 and PM-2 have different sets of flaws that keep them from playing in the first league and that's a shame because I know, they could.

Very interesting that you've measured that peak as higher than the average response. That very well could be more accurate and explain why I found it as bothersome as I did. I think your other points make a lot of sense as well.

I don't want to oversell my mods or my knowledge on the matter. There are a lot of people on this forum alone that know so much more about audio than I do and could surely whip up something better! Much of what I know I've picked up from others. What I've done with the PM-2 is about as simple as it gets...some open-cell foam in front of the driver, and I stretched them out for less clamp. They sit on my head rather lightly now, which makes a big difference in comfort and sound. That's about it! Which I suppose does make me wonder what some of these companies are doing in their R&D process, you know?

His impressions sound like the original PM2 pads we heard at the Bay area meet.  Annoying treble with disjointed overall signature. 

I didn't want to say this myself, but that was actually a thought I had. With all the iterations of the PM-2 pads, the thought that perhaps I received something that doesn't match the latest production run certainly crossed my mind.

Down the road, I hope to get some of the final alternate PM-1 pads for comparison.

I'm wondering what the PM-1 and 2 would have sounded like with better tuned, angled, thicker, velour pads.
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Oppo PM-2 Mod/Tweak/Stretching Measurements
« Reply #37 on: August 15, 2014, 01:59:20 PM »

Not being truly content with the PM-2 in its stock configuration, I set out to see if I could tweak it at all for better subjective performance. Well, in truth, I mod about every headphone I buy in one way or another. I did a lot of rapid experimentation on the PM-2, mostly in regards to different materials rather than wildly different tweaks. For now, I wanted to stick with simple, cheap, reversible mods than only required one to go as far as removing the ear pads. I've settled on something that I think sounds pretty good and is certainly an improvement over the stock PM-2 to my ears.

For this post, I'll detail subjective impressions and provide measurements. Next post will have comparison measurements with the stock PM-2, for your convenience, and details plus pictures of the actual tweaks themselves.

Background

There were two main things I thought the PM-2 could further improve on (keeping in mind MY tastes), assuming one wanted to keep the overall characteristics and sound signature (not trying to make these into something they're not). First, the treble needed to be smoother and had a narrow, sharp peak at 8KHz. As you can see, purrin didn't have a problem with it, but I did. Product and pad variation could potentially play a role, as Anaxilus mentioned. Second, the PM-2 was still a bit veiled, constricting sounding, and lacked air.

Flattening out the 8KHz peak is rather easy. A number of various damping materials, including toilet paper, felt, and open-cell foam do the job. But you'll affect more of the sound than just that, and I found it a bit hard to implement any of these tweaks in front of the driver without veiling the sound too much. That said, a bit more veil to have smoother treble seemed a worthy compromise, at least, if you found the treble annoying like I did.

I also noticed that simply lifting the PM-2 off my ears a little bit brought a better sense of detail and air. This coupled quite well with basic front damping tweaks. So, I bent the headband, at the top and where it starts to meet the cups, in order to widen the space between the cups and dramatically reduce clamping pressure. They sit very lightly on my ears now, just enough to make a good seal without effort. This also improved comfort a lot, but they will slip off your head more easily. If you have a smaller head than I do, you may already be good to go here. I am, after all, taller than most at 6' 3". It generally follows I also tend to be proportionally bigger than most (am very skinny, but not a "small" person). Maybe. *shrug*

Sound

With my basic front damping tweaks and having reduced the clamp to a considerable degree, there is simply a clear improvement across the board on the PM-2 to my ears. A more natural and effortless sound. Less strain, and a bit blacker. Tonality and timbre seems good, if not ever so slightly rough or lean. Mids seem to be filled in a tiny bit, but still on the laid-back side. Treble sounds smoother, more detailed, and more airy. Soundstage has noticeably widened, and placement of elements has gone up a notch. Better separation. Excellent balance overall and a joy to listen to. If I could fix one or two things, I think the treble still has a slightly rough quality to it, and the bass could use a bit more power and weight. Bass has been reduced a bit with the clamping reduction, and it still retains their light-footed nature.

This is what the PM-1 and PM-2 should have been, to my ears, IMO, YMMV. I wonder how the PM-1 would have done if I had simply done the same clamping reduction tweak, as it had an overall smoother and better looking response. Just tilted to the dark side too much. Hmm...

Measurements

As you can see, the 8KHz peak is no more! Instead, we now have a broader, less su bjectively troublesome peak at 10KHz. As I hear it, this is nicely balanced with the rest of the spectrum and greatly helps with giving a better sense of detail and air.

The dip around 5KHz is better filled out. Personally, I think my measurements from my left ear better captured how the PM-2 performs here. The first two "raw" measurements of the left channel, blue and green, are taken from my left ear and have less of a dip around 5KHz. In the case of the PM-2, I think the results from my left ear are a closer match to what I hear subjectively, and they do skew the averaged result in the end. Worth keeping in mind, though you may disagree subjectively if you hear the PM-2 yourself.

I did make one slight further tweak to my settings in ARTA for measurements, and I think that's accounting for most of the lower harmonic distortion you see here vs. the stock measurements. Stock should probably show THD results closer to this. However, it is my experience that front damping mods often help with reducing THD, so it's probably a mixture of both. Either way, aside from the known HD spike, you simply don't have to worry about distortion on the PM-2 regardless of what my measurements indicate. Simple as that.

CSDs still look good. A little better than stock in some ways, but it's close enough that it could just be measurement variation.

Listening to these as I write, and, again, a very good, natural sound. More details in next post.
« Last Edit: August 15, 2014, 04:45:59 PM by hans030390 »
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PM-2 Tweak Details
« Reply #38 on: August 15, 2014, 02:17:16 PM »

I used two specific materials for my tweaks. (BTW, this site is great if you want to experiment with a lot of different foam materials. Pretty cool seeing how they all affect the sound in different ways. I bought a bunch of random crap in bulk for cheap.)

White Poly Open-Cell Foam, 1/4" - http://www.foambymail.com/P/poly-foam.html
Charcoal Open-Cell Foam, 1/8" - http://www.foambymail.com/CF0-125LF/1-8-inch-charcoal-regular-foam.html

First, I cut a donut shape out of the white foam that would fit in the ear pad's bottom opening. The hole in the middle is cut for the driver's nipple-nub. Next, I cut a smaller circle out of the charcoal foam. I put this on top of the white donut's opening. This was then inserted into the bottom opening of the pad. I only took pictures of it on top of the driver itself so you could get a better idea what it looks like. Easier to put it in the pads when installing, plus it's cut to fit that anyway.

Then, I simply stretched out the headband and such to reduce clamp. They sit very lightly on my ears now but still seal perfectly. Done! The clamping tweak was what did it for me in the end. Otherwise, the damping mods, while the really smoothed the treble, were too subjectively veiled.

Clearly, this is super simple, cheap, easy to do, reversible, etc. etc. It's also pretty easy to make variations based on this to better suit one's personal tastes. Could someone else with more knowledge and better materials come up with a greater mod? I have no doubt. Still, I'm really enjoying them with these simple tweaks. I'm not even sure it will be worth tinkering with the insides at this point.
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Re: Oppo PM-2
« Reply #39 on: August 15, 2014, 03:29:23 PM »

It looks like a Paradox now.
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