It’s a good day for anyone with an interest in inexpensive headphone amps! The Liquid Spark, currently available through Monoprice for a penny shy of $100, occupies the same market space as the Schiit Magni 3. I found the Magni 3 to be a great sounding amplifier, and it really set the bar for amps in its price range. I’m happy to say the Liquid Spark is a worthy competitor. (TL;DR at bottom.)

The amps seem near identical in form and function. Both are solid state, have pre-outs, have a gain switch, are of a similar size, and utilize an external power supply. I had no issues driving my HD650 with ease on both amps, so they both have plenty of power to spare for about anything you might toss at them.

That the two products basically do the exact same thing on a functional level is good, because it makes the review easy by allowing me to only focus on sound quality.

If I had to generalize right off the bat, I’d say the Liquid Spark sounds a little more like a good tube amp, while still clearly not being a tube amp, whereas the Magni 3 sounds a little more like a good solid state amp. That said, they sound more similar than not, especially if you take a step back and hear their similar tone and presentation in a broad scope: slight warmth, agreeable treble, but close enough to neutral to not necessarily be called colored.

The Liquid Spark has a more spacious, layered sound and gives the midrange more room to breathe as it wishes. It’s a little more laid-back sounding. Again, not too unlike a good tube amp here. The Magni 3 retains a common characteristic I hear from many Schiit amps in that it’s rather forward sounding and a little two-dimensional at times.

However, the Magni 3 does benefit from its forward nature in that it’s a more dynamic and engaging sounding amp. While I’m likely to give the nod to the Liquid Spark for micro-dynamics and nuances, the Magni 3 excels with a sense of muscle. That’s not to say the Liquid Spark isn’t dynamic. It drives the HD650 without making it sound lean or strained, so it has plenty of weight to throw around on its own.

Interestingly enough, I find the Liquid Spark to have slightly cleaner, tighter sounding bass. It took me a while to get over the Magni 3 sounding more powerful in the low end, a main contributor to a sense of macro-dynamics, but inevitably the lower octaves on the Magni 3 started to sound a tiny bit rounded and bloomy in comparison. Still, both have that characteristically clean low-end as you’d hope to find in a good solid-state amp, so I’m splitting hairs here.

Circling back to my comments on the midrange, that’s where I really found the Liquid Spark to do what it does best. The Magni 3’s midrange and treble response can at times sound a bit strained or have the slightest sheen to it, despite being an overall warmer and very agreeable sounding amp. This is the sort of quality you really only notice in direct comparisons, so it’s subtle. The Liquid Spark, on the other hand, has more of an organic ease to the sound, giving everything a natural tone, timbre, and plenty of space to ebb and flow naturally. It has a more natural sense of space, captures reverb a bit better, and sounds a little more graceful overall.

It’s that quality, along with the spacious, airy nature of the Liquid Spark, which reminds me more of a good tube amp. The downside is one might find the midrange and treble to be a bit softer or bloomier sounding than they would like. Nonetheless, I found the amp to never lose details and nuances, as its overall resolution was quite good and at least as good, if not slightly better, than the Magni 3.

If I had to nitpick in one other, related area, it’s that the Liquid Spark’s airy sort of nature can at time give the sense that its background isn’t as clear or black as it should be. The Magni 3 does well in this regard. Though it would up the cost dramatically, perhaps the Spark would benefit from a LPSU?

Overall, the Magni 3’s characteristics are a little more brute-force-like. This plays into its strengths (power, macro-dynamics, engagement, clarity, sharpness) but also its weaknesses (a little too forward, slightly bloomy bass, slightly strained mids and treble in specific use cases).

The Liquid Spark seems internally work with more ease and less intense focus. Again, its strengths are the tube-like midrange and treble performance, clean bass, spaciousness, nuance, and so on. But those wishing for an incredibly sharp and focused sounding amp may want to look elsewhere.

Personally, I’m a little fonder of the Liquid Spark’s presentation. It strikes a really nice balance across the board to my ears. I wouldn’t go so far as to say it’s outright better than the Magni 3, because tastes will play a big role here. Simply put, they’re both excellent amps with an insanely low price point. I’m still amazed at the sound quality both amps offer given their price relative to common offerings from even a few years back. Take your pick, and either will suit you well!

TL;DR

- Comparing to Magni 3, since they basically occupy the exact same space in market (price, function, etc.).

- Spark is a little more tube-like, with a more spacious, layered sound, liquid mids and treble, and a more graceful sound overall. Better micro-dynamics. But some may find its mids and treble just a hair too soft.

- Magni 3 tends to brute-force the sound more, being more forward, aggressive, having greater macro-dynamics, but also has the benefits of sounding more focused, sharper, clearer, and having a blacker background. But it does sound a little strained compared to the Spark.

- Both have similar overall tone, i.e. slightly warm, agreeable, but not too far off neutral.

- Magni 3 may have slightly more rounded bass.

- Both are a steal at $100. Just pick what suits your preferences best.

- Spark may benefit from LPSU, but you’re looking at a significant price bump then.

OPPO has taken an interesting approach to their product lineup and launch timeline compared to what I feel like I’m seeing from most other manufacturers. OPPO started with the pricey PM-1, which I thought sounded pretty good, if not overpriced and a bit sleepy sounding. They then moved to the PM-2, which was essentially just a PM-1 with cheaper build materials and without the pretty wooden box. It was an interesting choice to start from the top and work their way down, not to mention how infrequently you see this copy-but-made-cheaper sort of product launch. But, anyway, the PM-2’s new pads and slightly refined internal damping, which Tyll at Innerfidelity brought to light, helped bring out a more neutral sound at the expense of some smoothness and refinement that I really enjoyed from the PM-1. I thought both models, while handsome and pleasing in many ways, just weren’t quite where they needed to be for the price.
 
OPPO continued their downward pricing trend with the launch of the PM-3. The PM-3 is meant to occupy a different headphone category than its older siblings. It’s still a planar-magnetic headphone, but smaller and more portable, easier to drive, and, oh, it’s closed instead of open. At $400, it gets close to being half the price of the PM-2. With the closed isolation and frequency tuning, it’s meant for a more on-the-go sort of situation, like in an urban or otherwise noisy environment, while still retaining some level of general balance. When you consider what OPPO was aiming for, I think they did a great job meeting their goals and then some. Sure, I have a few minor quibbles, but for all you get at the price point, there’s not a whole lot to complain about.
 
Comfort, Looks, Build Quality, and General Presentation
 
It’s no surprise that the PM-3 is a nice looking headphone with good build quality. Like the PM-1 and 2, it has a sleek, simple, and modern look. It shares a lot of their physical traits and design elements, actually. Lots of black and grey with a healthy mix of plastic and metal, though now you have the option of a white PM-3. Both color options look great in person. The brushed metal back is a nice touch. The PM-3’s edges aren’t quite as rounded as you get on the PM-1 or 2, but it’s almost not worth mentioning.
 
I do not like that the pads are not removable on the PM-3. I have to imagine there are ways to keep the same level of pad seal while allowing easily removable pads, but, hey, I didn’t engineer these. I just hate pads I can’t remove myself and always will.
 
UPDATE: See comments below. Looks like the pads are removable, but it's not the easiest method around.
 
Comfort is not bad on the PM-3. The PM-1 and 2 are more comfortable due to larger and deeper ear pads. If your ears are on the larger side of things or stick out, you may have difficulties getting the PM-3 to fit around your ears perfectly or have issues with your ears touching the inner lining of the pads. I think most will be fine here, but it’s something to keep in mind. Personally, it’s the clamping force that gets me. It’s a bit strong out of the box on the PM-3. You can bend the headband to adjust for this, but do make note that this may impede the PM-3’s ability to get a good seal and produce the strongest bass it can. If you have issues with its clamp, play around with bending the headband until you get it right. It’s a sturdy headphone, though do treat it with care nonetheless.
 
Like the PM-2, the PM-3 comes in a classy looking box, but not a wooden one, and includes a nice denim case. Coupled with its sleek looks and strong build quality, the PM-3 fits right in with the rest of the OPPO lineup. It feels like a premium product. When you consider the price, I think you get more than what you’d normally expect in these areas. But what about the sound?
 
Sound Quality
 
Remember that the PM-3 was designed to work well for loud environments. It has inherently decent isolation and a tuned frequency response to work best for its intended purpose. When I first put the PM-3 on, I thought it had powerful bass and was a little bit bright. It doesn’t exactly have a U-shaped sound signature, but it’s not entirely neutral either. The slight brightness is certainly outweighed by the low end response.
 
The PM-1 and 2 always had some extra warmth to their sound, but they were generally flat or slightly thick at best when it came to low bass. With their rolled-off top end, both sounded a bit mid-centric and, at times, a bit sleepy. The PM-3 is not that. Compared to the PM-1 or 2, it kicks the bass up a couple notches and has a less warm tonality. Once you get into the low-mids and upper-bass of the PM-3, the response just gets stronger and stronger the lower you go. It has a lot of kick and impact. Generally, the bass on the PM-3 sounds strong and powerful, though at times it can get a little thick sounding. Think perhaps a bit too full-bodied rather than too muddy. But for a headphone being so bass-heavy, I actually think it’s more clean than not. It trends a fine line, really.
 
However, I have heard some say they do not hear the PM-3 as particularly bass heavy. I think there are a few possibilities that can explain this. First and foremost, the PM-3 is very sensitive to getting a proper seal if you want the full bass output. Even thin glasses have a measurable effect on the bass output. I don’t think it’s too difficult to assume, then, that even certain styles and lengths of hair or particular face shapes and features might prevent one from getting a perfect seal on the PM-3. Or it could even be different ear shapes and sizes affecting perceived response. Then you must consider how some judge bass differently. Some focus more on the upper-bass than the low-bass when quantifying it. Some also come from backgrounds with headphones with even more bass or, perhaps more commonly, headphones with higher distortion in the bass (which will often give the perception of more or stronger bass). Let’s also not forget the possibility of product variation, though I get the feeling OPPO is pretty consistent. You can see that trying to understand varying opinions can get tricky quickly.
 
The midrange as a whole on the PM-3 is relatively clean, clear, and neutral. With the strong bass and slightly emphasized treble, it might sound a little recessed to some. I don’t necessarily hear it that way, but there are a couple different ways you could look at the PM-3. I think it could be slightly better integrated with the bass and treble, to a lesser extent, but that’s just me nitpicking.
 
Treble on the PM-3 is interesting. Throughout the entire range, it never quite reaches the strength of the bass output, so any extra emphasis still doesn’t stick out too much. And emphasis or not, the treble is smooth and clean sounding. So, sure, it can be a touch brighter in spots than normal, but it rarely sounded harsh or too fatiguing even for someone with laid-back tastes like myself. The general treble emphasis on the PM-3 lies in that upper-mid to lower-treble transition area, not too unlike what I heard on the HD600. It’s not lit up quite like the K7XX, for those familiar with that headphone. If anything, the upper-treble on the PM-3 is a tiny bit rolled-off. I don’t hear anything as missing on the PM-3, but relative to some other headphones, it might lack that tiny last bit of sharpness, sparkle, and clarity you get from the upper-treble.
 
The PM-3 will never be the airiest or most expansive sounding headphone. It’s closed and on the intimate side of things. The soundstage is well integrated but a bit small. There’s not a ton of depth to the sound, but layering is thankfully not particularly blurred.
 
Sure, the PM-3 might not be quite as balanced tonally as the PM-1 or 2. It’s a bit cooler sounding and has a more “fun” sound signature. But, damn, it’s fun, engaging, and addicting to listen to! I can see this working really well in a louder environment, which I have not yet had an opportunity to really test it in yet.
 
In fact, the PM-3 actually has some improvements over the PM-1 and 2 to my ears regardless of having a more “fun” sound or not. For one, it seems to have more clarity across the frequency spectrum than its predecessors do. Transients seem faster and cleaner. Low-level details aren’t quite as masked. The PM-1 and 2 just have an inherently slower sound in comparison. No doubt, the PM-3’s frequency response plays into this perception, but I think it has some genuine improvements outside of that. For one, distortion seems better on the PM-3, but I’ll get into this in a bit. The PM-3 just seems to sound a bit cleaner and clearer in most ways than the PM-1 or 2. Snappier, if you will. Simple as that.
 
All in all, I think OPPO came close to nailing what they were aiming for. The PM-3 is not inherently meant to be the most neutral headphone ever, and that’s fine. It has a really engaging sound and seems to make some technical strides over the PM-1 and 2. Ideally, I think the treble response could be evened out a bit more so it’s not quite as bright sounding, and the mids could sound a bit thicker and better integrated, but I’m really nitpicking and don’t have much room to complain when you’re already getting so much at $400.
 
Let’s take a look at how they measure for me.
 
Measurements
 
First, I would like to mention a couple things about my measurement setup and methods:
 
- I use an in-ear mic for measurements, and my results only compensate for an inherent bass roll-off from my mic’s PSU. As such, these results are meant to at least somewhat match what I hear, given the coupler is my own head and ears. Since your ears and head likely aren’t physically identical to mine, you may hear things differently. My results are more meant to emphasize my point of view, not be some sort of averaged or absolute truth for all. Also note that flat on my setup generally means flat. No need to over complicate reading these.
 
- If possible, I take measurements of each channel from both ears. Given the PM-3 has a flat style ear pad, this is possible. I take four measurements of each channel from each ear, totaling to eight measurements per channel. These are then averaged.
 
- Harmonic distortion results are inherently limited in my setup and really only good for showing major problems. Results below 100Hz can be hit and miss as well and are the most limited or bottlenecked portion of my measurements.
 
- If you’ve seen any of my other measurements floating around on the internet, the PM-3 measurements are only comparable with other results from this year. Why? Because I got a new in-ear mic that I can fit deeper into my ear canal. This generally means I get more treble in measurements with my new mic. So, if you see anything from me that I measured last year, just make note that it’s not entirely comparable to results of anything I’ve measured from this year. There are more similarities than not, but for the sake of keeping things simple, try not to worry about comparing ’14 and ’15 measurements.
 
Now, with that said…
 
Frequency response results show a strong bass emphasis that is about 8 or 9dB up from the 1KHz point at 20Hz. It has a fairly linear decrease to the 300Hz point. I think the PM-3 could use a bit smoother transition from bass to mids, even if it meant you get more warmth in the midrange. It’s not that the bass sound disconnected, because it doesn’t, but the tuning does make the midrange sound a bit thinner than it could otherwise. The midrange is largely pretty good, though you can see that upper-mid through lower-treble emphasis I heard during listening tests. Personally, measurements are what they are, but I didn’t hear the PM-3 as rolled sounding at the top end as the graph makes it look like. Lacking air, yes, but not particularly rolled.
 

 
If you look at Tyll’s measurements for the PM-3, you can see how one might hear parts of the midrange as a bit depressed and disconnected relative to everything else. And depending on how you look at his results, especially the raw results, you might be able to see a bit of that upper-mid through lower-treble emphasis relative to some other headphones.
 
Here’s a quick look at how the response changes when I wear thin glasses. As you can see, even a small leak in the pads, and I do mean small, causes a noticeable drop in bass. Ignore that the response doesn’t look exactly like the graph above. This was just one quick measurement take for easy comparison’s sake, not a full set of averaged measurement takes. This was also just from one channel (left, I think).
 

 
Harmonic distortion results are pretty good as a whole. Keep in mind that the bass distortion creeps up because the response as a whole becomes more and more elevated as you go down the spectrum. It’s all relative. But, still, my setup is limited here and generally is the bottleneck for bass distortion results in low-distortion headphones. Tyll’s harmonic distortion results look pretty good and, interestingly enough, get very low at 100dB! Oh, and what’s this? No 300-500Hz distortion spike like the PM-1 and 2! Might play into the PM-3’s clean sound.
 

 

 
CSD results for the PM-3 are pretty good. Not the absolute best I’ve seen, but nothing to complain about. Naturally, the treble spots that are a bit emphasized aren’t going to decay as quickly as other spots. Left and Right, in that order.
 

 

 
Next up is the eight measurement takes that I averaged together to get the full frequency response measurement. Differences in various takes are largely due to in-ear mic insertion depth, though the headphones placement and fit does play a bit of a role too. Whereas Tyll moves the headphone to account for different placements, I have tactile feedback to let me know if a headphone is fitting right and like I’d normally wear it. Maybe you’ll find these raw results useful, and maybe not. But here they are.
 

 

 
Conclusion
 
I think the PM-3 does really well for its targeted, on-the-go sort of sound and price point of $400. I find them very fun and engaging to listen to, if not a touch brighter than I’d like at times. Think of them a treading that line between being somewhat neutral and natural sounding and the typical U-shaped, fun sound signature. It’s more the bass emphasis that makes them less than neutral than the slight treble emphasis, but, hey, the bass can actually be pretty fun. Measured results look pretty good for my setup. No terrible surprises or anything of the sort.
 
With the generally good sound quality, sleek looks, strong build quality, and overall premium presentation, I think the OPPO PM-3 is a great headphone and worth your consideration if you’re in the market for this sort of headphone. Sure, I’d like to tweak a few things before calling them perfect, but I highly recommend the PM-3.

Disclaimer: I received the Brainwavz HM9 under the condition I would write a review for it. I set the purchase price at the current going rate on Amazon, which is roughly $120.
 
Introduction
 
The Brainwavz HM9 was always a headphone I was curious to try, but my curiosity wasn't strong enough to warrant a purchase. Thanks to the review sample provided by Brainwavz, I was finally able to check them out! Sure, I always thought they looked stylish, but I had no idea how they would sound. Onto the review and analysis!
 
Looks, Presentation, Comfort, Build Quality, Misc.
 
I really like the look of the HM9. They're a bit more unwieldy on my head than I initially expected, but, eh, they look like fairly high quality and classy headphones with the black and silver scheme and overall design. I was surprised to find they're more on-ear headphones than over-ear. In fact, I can't get my ears in these at all! The cups and ear pads are smaller than I expected (the unwieldy aspect comes with how wide they are from cup to cup). Ah, well, no worries. The pads are quite plush, fairly comfortable, and still seal around the ears once you give the foam a few minutes to warm up and conform to your head and ears. The cushioning on the headband also seems plush enough to make these comfortable for a good while. They're not the most comfortable headphones ever, but they do well enough.
 
Going back to looks, I have to admit that the HM9 feels cheaper than it looks. The cups are clearly made of a thin plastic, and there is a bit of creaking in areas of the headband assembly. It feels sturdy enough, though, and I'm not worried about them breaking. And while the headphone does fold up, I wish the cups could swivel from side to side, as they are stuck sitting parallel to your head. This makes getting a good, comfortable fit a bit harder than I'd like.
 
I do like the accessories that came with the HM9. Removable cables are always a nice touch, and the HM9 comes with plenty of them! One cable even has an inline mic. The carrying case is nice and works well too! I'm always happy with the accessories Brainwavz includes with their products. It's a nice touch.
 
Sound
 
Based on the HM9 descriptions and some other impressions I had read, I expected a fairly warm and colored headphone. That turned out to be true (and then some), but I was still a bit underwhelmed with the HM9's overall sound quality. It's not that it isn't enjoyable, but it isn't very refined even for a colored headphone, and I know of at least one direct competitor with a similar sound signature that does better overall. Let me go into further details.
 
The first thing I noticed about the HM9 was the bass. There is lots of bass, and in particular lots of mid-bass. This gives the headphones a sort of thick, "wooly" quality that even bleeds into the midrange. In a sense, it's as though everything is going "woh" or "woof" even when it shouldn't be. I also thought the left channel had subjectively more bass than the right. My guess is it's caused by the single-entry cable in the left cup that is causing leakage and internal cup differences.
 
The midrange and treble seemed to be a bit better balanced than the bass, but some aspects were still off. Something in the low-to-mid treble was a bit rough sounding, whether it be some sort of peaky nature and/or extra resonance and ringing in that area. On the other hand, it sounded like the top bit of the treble was noticeably shelved, so the headphone sounded both rough, dark, and laid-back at the same time. And bassy.
 
Even with these issues and the bass clouding things up, you can still sometimes get a good sense of speed and detail. It depends on what you're listening to and listening for. There will be moments you are listening for something and are surprised by how well it comes through, and other times where you're listening for something and it doesn't manifest itself so well or at all. Interesting. I also found the soundstage to not be too bad and the sense of reverberation to be decent. This was surprising to me given the bass boost and treble veil in some areas, but I'll take it.
 
Aside from the boosted bass and rough treble area, there are still some promising signs. Bass can be a bit one-note sounding, but still has OK detail and never gets too boomy or rumbly. My guess is it has decent distortion and just a boosted bass response. The mids and some areas of the treble sound fairly detailed and clean, but they are easily clouded by the poor aspects on the headphone. Some genres do work better on this headphone than others due to its colored and rough characteristics.
 
In the end, I still found myself enjoying the sound of the HM9, but not so much that I could really recommend them. For the sound signature they were targeting, I think they went a bit too overboard in spots, and there are some rough aspects that make the HM9 sound much less refined than some similarly voiced headphones. For example, the Logitech UE6000 has a similar bass boost, but it is cleaner and better integrated with the rest of the spectrum. The mids and treble on the UE6000 are fairly balanced and clean as well. So, it's voiced in a similar way, but it just sounds so much more refined than the HM9. Given you can find that for less than $100, I find it difficult to consider the HM9 as a super viable purchasing option. (I have taken measurements of the UE6000 several months ago, but I will need to re-do them if I ever want to post them publicly. They did confirm what I hear subjectively.)
 
Measurements
 
Frequency response measurements are not surprising. Large bass boost centered around 100Hz. At its peak, it is about 11dB higher than the 90dB point at 1KHz (left channel), which is where I calibrate my headphone on the left channel for measurements. Channel imbalances also match what I heard, but it's not too bad above the bass. Treble response is pretty rough and uneven overall. There's an emphasis around 3KHz, a peak around 7KHz, and a large treble recession around the 10KHz area. Even for a fun or colored headphone, much of this is fairly poor.
 

 
Harmonic distortion is generally fairly low relative to the frequency response. I do see some spots where it hits around 1% THD in the bass, and 3rd-order distortion starts to creep up a bit below 200Hz, but these results are not too bad overall.
 


 
CSD results are a bit skewed given how depressed the treble is relative to the bass. Still, it looks like the HM9 doesn't have too many resonance or ringing problems except for that ~7KHz peak area (don't worry so much below 1KHz). I've heard ringing that is more sustained over time than this on other headphones. Since this ringing spot decays before 3ms, you will hear some roughness and extra edge around that area, but it won't sound so much like it is continuously screeching at you at that point. (Pics are left and right channel, in that order.)
 

 

 
Raw measurements indicate a headphone that is fairly stable when it comes to bass performance, which is good given how these are basically on-ear headphones. Treble performance does show some variability with placement and fit, but nothing too wild. You might be able to find some positions on your ears that sound slightly better.
 

 

 
Conclusion
 
I like how the HM9 looks, and I like the accessories it comes with. It did feel cheaper in quality than I expected, but it doesn't feel like it will fall apart easily. I did find the sound enjoyable despite the issues I mentioned, but it still has too many rough patches and perhaps too exaggerated of a bass response for me to recommend it even if you are looking for a colored, bassy headphone. I don't hate or love it by any means, hence the middle of the road review score. The looks and accessories brought the score up a tiny notch. If you want a bass-heavy headphone around $100, the UE6000 will fit the bill with a much more balanced midrange and treble response (it comes with a carrying case and inline mic on the cable as well).
 
(I did try some damping mods on the HM9 and was able to get the bass response much lower, but the treble response is still quite uneven and difficult to improve. I thought they might have some modding potential, but I was left disappointed there. But, if you have an HM9 and are looking for some damping ideas on how to lower the bass response, feel free to PM me.)

Disclaimer: I have been talking with Zach of ZMF Headphones quite a bit over the past couple months with some ideas that might help him refine the ZMFxVibro headphone based on my thoughts and analysis of it (have tried a couple pairs and couple revisions), so there’s bound to be some inherent bias in my opinion. However, I do strive to minimize any bias and take pride in trying to provide the community with honest, transparent reviews and at least a somewhat objective, but digestible, analysis of products. In other words, I'm trying to break the mold compared to what you get from typical industry insider and/or overly-excited reviewers. I am in no way affiliated with Zach or his ZMF Headphones company, nor have I or will I receive anything whatsoever from our discussions, any ideas we've shared, or this review. 
 
This is a loaner pair that I am reviewing. This review is based on the latest tuning as of mid-September, which should be the final revision except for a couple other changes that won't affect sound quality. More on that later.
 
This review was posted elsewhere on the internet a few weeks ago and has been edited and refined in some ways.
 
Introduction
 
I wasn't sure what to expect from the ZMFxVibro when I first got a chance to listen. It had a lot of promise, but I thought it needed a couple tweaks to smooth out the treble. I experimented a bit and found something that really made the ZxV sing...just some basic front damping. Zach happened to contact me, we had some good discussions about the headphone, and we tossed some ideas around. A few weeks later, he sent me a set of revised headphones with some internal and external damping changes, including some new front damping (the key factor). I was curious to hear how his changes sounded compared to the previous pair I tweaked on the front side a bit, which I had quickly grown fond of. I was happy to find that the changes with the new pair were to my liking...surprisingly so. I thought they sounded pretty darn good! But, let me not get too hasty with those details just yet, so I'll get back to the sound and even offer some Alpha Dog comparisons in a bit.

Looks, Comfort, Build Quality, Presentation, Misc.

I have to say, I think these are a good looking set of headphones, though I like the look of some of the other pairs on the ZMF site even more (Zach wasn't crazy about how porous the type of wood on this particular pair was). On this tour unit, the blue finish and particular type of wood makes for an interesting and, in my opinion, beautiful look. You’ll recognize the classic T50RP headband, and ZMF offers custom re-finishing on the metal railings as well. There is a nice set of finish options, both wood and railings, to choose from. Here's a shot of this particular pair, though it doesn't do it justice in any way (screenshots on the ZMF site are much better):
 


The variable bass-tuning port implementation works fairly well and does what it is supposed to. Essentially, it offers 4-stage tunable bass with the 3 ports (fully closed to fully open). While I prefer the implementation that allows you to finely tune the Alpha Dog, the ZxV’s venting options is much more convenient to utilize despite being less granular. And where as the AD isn't meant to be tuned more than once or twice, and is harder to get perfect without fine tuning, the ZxV's solution lets you adjust the tuning on the fly. Of course, there are other headphones with tuning options, and I even remember seeing some early T50RP mods with similar ideas.
 
I found I preferred having one port open per channel on the ZxV, as having them all closed made them a bit too weak sounding, and any more made them too bass heavy for my tastes. Having more ports open can be fun at times, though, and I think it's great to have that option for those with varying tastes. To be fair, Zach was targeting a headphone that could be rather bass-heavy and lush sounding. My impressions and measurements were done with my preferred configuration, only one port open. One downside to this venting setup, however, is that it’s pretty easy to lose the dowels if you aren't careful. A good example would be if you're adjusting the headband sliders and rub your hands against the dowels. There's a good chance some will pop out.

Thanks to the alpha pads and padded headband, the ZxV is a fairly comfortable headphone. I still think the Alpha Dog itself is a bit more comfortable and fits better on and around the head with the suspension-like comfort strap, as the ZxV’s wood cups and overall method of construction make for a more rigid headband and fit. The main factor, as I see it, is that since the cups are entirely rounded, there is no recessed spot for the headband rails to bend near the top of the cups for fit purposes. The way the headband screws into the cups might also be too rigid. Good thing the T50RP headband can be bent without much worry. With some brute force, I was able to bend the headband to a shape that gave me a good fit and seal, if not yet quite perfect like the AD.

Overall, the Alpha Dog feels like a more premium, well put together product, and the ZxV has a distinctly hand-built look and feel to it. Still, the ZxV does have its aspects of beauty and is certainly more than functional in all the non-sound areas, so I'm really more concerned about how the headphone sounds when all is said and done. ZMF does offer some other optional accessories to purchase along with the ZxV, such as a nice, hard carrying case and braided OCC cables.

Sound

I think the ZxV is a very enjoyable headphone to listen to, plain and simple. They are a bit on the bass-heavy, slightly dark side, but generally have a surprisingly good sense of balance and neutrality to them. Mids are not scooped, and treble detail doesn’t appear to be missing despite it being a touch dark in spots. Perhaps the ZxV is not too far off the HD650 in that regard, though it is less laid-back sounding. At times, the bass can be a bit disconnected sounding on the ZxV, but the sound does tend to be rather cohesive as a whole. I thought the bass sounded fairly clean and offered good pitch and detail. With one port open, sometimes I wish it was still just a bit less powerful, but I often like the tasteful bass bump. It makes music sound lively, and the T50RP can start to sound weird if you start lowering the bass too much, even if it measures flat. Perhaps this is due to the small, planar driver, and maybe the driver has a need for some amount of venting

Subjectively, something about the upper-mids and treble can be a bit edgy sounding, not unlike how the HD600 can be at times. The ZxV also can be a touch harsh or, perhaps better put, hashy sounding, but this never really bothered me or got in the way of enjoyment for long listening sessions. It’s probably just my quite sensitive ears given how slight it is. It's more noticeable coming from smoother sounding headphones. It was still smoother and less artificial sounding than the Alpha Dog and maybe sits somewhere between the HD600 and HD650 in terms of edginess and smoothness.

That said, I do think the ZxV offers a good sense of clarity and blackness, more so than the Alpha Dog. The ZxV might also be a faster and more resolving headphone than the AD. I often found the ZxV did a slightly better job pulling out low-level information, and it did a better job on one of my sample tracks by bringing out the fast snare beat and associated detail (blast beat section of a metal song, very easy to muddy up). If anything, despite being a bit less neutral sounding (except for bass), darker, and lusher than the AD, it has bit more of a “hi-fi” sound to it. Don't get me wrong, as the ZxV is still quite neutral to my ears. The AD noticeably excels when it comes to soundstage over the ZxV, as the ZxV is more on the closed sounding or intimate side, but the ZxV does seem to do well or even better with separation regardless (and that extra sense of clarity helps). I found the ZxV to be a fairly organic sounding headphone when compared to the other headphones I have on hand, which is something I prefer over the AD’s presentation. I might even find it more organic sounding than the HD600/650, even if you dampen and mod those Senns, but it’s hard to say and depends on my listening mood. I think the ZxV has pretty good tone and timbre to it, and one I almost always preferred over the AD. I wrote a note saying the ZxV can be a bit nasally at times. I guess that is true, but very minor and no worse than niggling issues I’ve heard from about any headphone.

The ZxV does appear to have a tiny bit of channel imbalance, but this is largely fixed if you fiddle with the fit and placement. Really, it doesn’t get in the way and usually isn’t noticeable. The AD suffers from this too to an extent, but perhaps less so. I think unless you are meticulously trying to match channels, there are some inherent limitations with the T50RP drivers.

Compared to the OPPO PM-2…I dunno, I think I just like the ZxV more in most regards. It makes the PM-2 sound boring and lacking something.
 
I also was able to test the Paradox Slants for a while, but those are not too comparable to the ZxV or Alpha dog, in my opinion. The Slants have more of a bass emphasis in the 100-300Hz area (a thicker, more wooly sounding bass), more relaxed upper-mids and lower-treble, and are generally just a bit more laid-back sounding in a way. The Slants are quite refined sounding, probably the best of the bunch, and look great, but they're occupying a different sound signature than the ZxV or AD. I haven't heard the regular Paradox recently enough to comment on it.
 
I might even prefer the ZxV over the HD600 or HD650 in back-to-back listening tests. Hard to say. Overall, despite the ZxV not being perfect, these are one of the more enjoyable headphones I’ve tested recently, and I did find myself gravitating towards the ZxV during my back-to-back tests. Very highly recommended from a sound quality perspective!

Measurements
 
Note: My measurements are not comparable with results you'll find elsewhere. As it stands, flat on my frequency response measurements sounds pretty flat to my ears (not necessarily your ears), so you shouldn't have to strain too much trying to figure out how to correlate these with my subjective impressions. I do not guarantee absolute accuracy of any of these results, but they are very useful at times. Roughly calibrated to 90dB at 1KHz on the left channel.

Frequency response measurements do show an overall slightly dark tilt, but the midrange is pretty good and even. There are some channel imbalances evident below the treble area, but I didn’t ever find this subjectively detrimental. I've seen this on other T50RP mods too to an extent. Keep in mind the scale of the FR graph is only 30db. Bass is a bit elevated, but sounds tasteful to me. The treble is a bit uneven and depressed in some spots, but that doesn’t seem to contribute to anything sounding particularly weird. Still looks better than the PM-2 to me and quite a few other headphones. That dip around 8-9KHz is probably a measurement artifact.
 


Zach and I have had some discussions about internal damping and reasons for this pair’s channel imbalances, and he is pretty confident current production pairs should match a bit more closely than this. Based on what I know about this pair and some advice I gave Zach from that, I’m inclined to think he is probably right, and it’s not anything that will affect the overall sound.
 
I don't think I grabbed measurements of other port tuning configurations, but it does what you'd expect by primarily lowering or boosting the bass response below 150Hz or so.

Distortion results overall look pretty good, especially on the right channel. Arguably smoother and cleaner, though not necessarily lower on average, than the AD’s results, which might contribute to the subjectively more “hi-fi” sound and clarity I heard. There is a bit of a rise in bass distortion, but this is still a pretty good result. The distortion spikes in the left channel didn’t seem to impart any negative subjective characteristics when I was listening, and, again, based on what Zach and I have discussed about the internals on this particular pair, this should be ironed out in current production pairs. Even if the channel imbalances and harmonic distortion oddities were to not be further ironed out, I don’t think it’s worth worrying about. (Remember, D2 = 2nd order harmonic distortion, D3 = 3rd, and so on. If distortion is 40dB lower than the response at any given point, that is roughly 1% distortion. 50dB is about 0.32% distortion. You can find calculators online for this. D2 is often equivalent to THD results.)
 



CSDs look pretty clean, which isn’t unexpected for a T50RP mod like this. The extra bit of decay around the 2-3KHz area might factor into the edginess I was hearing, but even that is pretty minimal. I don’t think most will have issues or even notice what I was talking about. There might also be some extra resonance below 1Khz that affects the sound. If you compare with the Alpha Dog CSD measurements in the review I posted for that headphone, you might notice the AD measures with a bit more resonance below the 1KHz spot or so. This might also contribute to the slightly more "hi-fi" sound I heard on the ZxV.
 


 
Raw measurements show us that the ZxV is a pretty consistent performer, though you can see some changes based on fit and placement differences. 
 


 
And now for some comparison frequency response measurements! For other comparisons (such as CSD or THD), you'll need to pull measurements from my other reviews or sources and compare on your own.
 
First up is the ZxV vs Alpha dog. You can see some similarities, but they are tuned differently. The AD has a bit more bass, less of a smooth bass-to-mids transition, and somewhat of an emphasis around the 5-6KHz region where the ZxV is a bit darker (I think this is part of the reason I prefer the ZxV's tone and find it a bit smoother on the ears). Both have a dip around the same spot in the treble, which makes me think this is an artifact inherent to the T50RP + alpha pads in combination with my measurement setup. Overall I think the ZxV looks a bit smoother and more balanced. They sound less similar than you'd think based on the graph, and I can only make guesses that they aren't using similar internal damping schemes or materials.
 

 
Figured I'd compare it to the classic HD600. Again, this might explain why I prefer the ZxV's balance.
 

 
Here is a comparison with the HD650. Interesting! I do like the HD650 quite a bit, and it seems the two headphones have a similar target curve above 1KHz. The HD650 is a bit more mid-bass heavy, not quite as lively sounding, and doesn't quite have the same low-bass impact as the ZxV.
 

 
Again, fairly interesting. The PM-2 sounds pretty "weak" in terms of impact and power compared to the ZxV, though you could argue it is more bass-neutral, and there is a noticeable chunk of missing treble information during listening tests on the PM-2 (see the PM-2's big treble recession). The PM-2 also has rougher sounding treble. Might not be as clear sounding as the ZxV. Personally, I had no desire to use the PM-2 when I had the ZxV on hand (keeping in mind I only really listen at my desk).
 

 

Conclusion

The ZxV might not have the perfect build or looks of the Alpha Dog or PM-2, but I simply really like how the ZxV sounds. The original pair I heard was a bit uneven and too harsh in the treble, and I think Zach did a good job targeting the sound he was looking for in the end with this pair. The ZxV now employs some front damping to help smooth out the sound, and I think the materials produce good results. Perhaps there is still room for improvement with other front damping materials and configurations, but I’m pretty satisfied with this. Oh, and if you get a ZxV and want more treble, try taking off some of the front damping material directly in front of the driver.
 
I was tempted to give the ZxV a 4.5/5 given how good I thought it sounded, but I'd like to see a bit more refinement in both how they fit on the head, which may require too much work with the cups as they are, and a bit more refinement in some elements of the sound, such as more tightly matched channels and tweaks to better ensure low harmonic distortion. Some of the hand-built aspects, while they have their charm, also keep me from going with a 4.5/5. So, with the solid 4/5 score, keep in mind that I still really dig how these sound and suggest you not overlook them! I'm excited to see what Zach is able to provide in the future.

Note: Much of this comes from a review I wrote and posted elsewhere a month or so ago, but with some editing and organizational tweaks.
 
I have wanted to do a full Alpha Dog review for a while, and now that my pair has had some work done on it to better balance the channels and I have had plenty of time to listen and experiment with them, I'm good to go. My pair came with two of the damping “dots” applied to the front side of each driver and the felt damping discs for additional tuning. My main review and analysis will be done without using any of the felt discs, though I’ll provide rough and basic results of what these tweaks bring to the table as well.

Presentation, Looks, Features, Comfort, Etc.

Presentation and looks are obvious highlights of the Alpha Dog. The cups look great and are beautifully painted. The new baffles work well and allow the pads to more seamlessly integrate with the entire headphone. Little touches like the black slider bars go a long way in making this feel like a premium product. And everything feels very sturdy and well put together, including the somewhat thick and microphonic cable. (It's a good cable, don't get me wrong.)

Also included are some basic accessories, such as a microfiber cloth, a hex key to tune the vents, and a headphone stand. I know some have complained about the height and size of the headphone stand, but given its historical roots in needing to fit a medium-sized, priority mail USPS box, I think it works well. For me, I have no problems with unplugging the cable and storing it in the middle section of the stand, though now that Dan has switched to other shipping providers, perhaps the height of the stand will be adjusted in the future. I thought it was a nice touch and don’t see much of a reason to fuss over it.

Speaking of the hex key, the tuning options available to the Alpha Dog are quite nice. If you find the sound to be too heavy or lacking in the bass, you can adjust the tuning vents with the included hex key (more on this in a bit). However, this does come with a disclaimer warning against tuning multiple times, as only once is recommended, and that MrSpeakers/Dan won’t be liable for any damage you cause. I believe you can get them re-tuned for a fee if you mess them up. Personally, unless you have really good ears or measurement equipment to verify tunings, I’m not sure how much I’d recommend this. Regardless, having the option is nice, and the implementation is smart and well-done.

Comfort is quite good on the Alpha Dog. Assuming the leather headband strap is adjusted to act more like a suspension headband, it evenly distributes weight across the head. You may need to shorten it a bit on your own for this, though this tweak might be the norm for recently shipped and new AD pairs. Clamping force is rather light, and the alpha pads are, as always, very comfortable. The Alpha Dog can get a bit heavy for long listening sessions, but it’s not at the level of some of the heavier orthos.

The packaging itself is rather modest, but it is efficient and gets the job done well. It at least matches the red and black colour schemes. Overall, I give the Alpha Dog high marks in the non-sound related categories. Perhaps the cable could be less microphonic, and perhaps the headphone stand could be taller, but I don’t think it’s worth worrying about. This is a great looking, well-designed, and well-built headphone.

Sound

It’s no secret that I was not a fan of the early Alpha Dog iteration I heard. I simply found them too uneven, peaky, and exaggerated in the treble. There was potential, but I just did not think the Alpha Dog was quite ready for launch in that state, as good as they looked externally. You are welcome to disagree with me on that point, as I know many were and are quite happy with the early pairs. Now that the new damping “dots” and felt discs are available, with most or all Alpha Dogs shipping default with one or two “dots” per channel now, if I am correct, I was pretty eager to check them out again. Whether or not any other internal changes have been made, I cannot say for sure.

The new damping tweaks certainly make a positive difference, in my opinion. Treble response is smoothed out and less harsh on the ears compared to the early revisions. If one desires an even darker, smoother sound, they can use the felt damping discs. For this review, I stuck to listening without felt discs and relied on the two “dots” per channel. Those "dots" do their job fairly well.

The Alpha Dog can be a bit difficult to adequately describe from a sound perspective at times. In most situations, it has a fairly neutral sound with some caveats. It does seem to have an inherent sort of hard or even slightly glaring aspect to the sound, most noticeable in how the upper mids and treble are presented. That’s not necessarily to say the Alpha Dog is a bright headphone, though it can subjectively be a touch bright at times. It’s not necessarily a problem with the frequency balance, resonance/ringing, or distortion. It’s actually quite hard to pin down, so I’ll just say the sound can be a bit fatiguing at times for reasons that aren’t always perfectly explainable. To reiterate and put slightly differently, the tonality and timbre lean towards sounding a bit hard and artificial. Thankfully, there are tuning options to mitigate this, and given I am more on the sensitive side of the hearing spectrum, I doubt most will find this problematic or hear it at all. Personally, one felt disc added per channel goes a long way for my ears, though many of the traits, positive or negative, still shine through. On the other hand, the felt discs still aren't quite perfect, in that they do take away some positive elements despite smoothing out the response. It will be up to you to decide what works best for your ears and what compromises you are willing to make.

The next thing that jumps out about the Alpha Dog is the bass. It is a fairly bassy sounding headphone, though not necessarily thick sounding. If anything, the elevated bass feels a bit disconnected from the rest of the sound. This is immediately apparent against other headphones with a flatter, more linear bass response. However, I think it is somewhat tasteful (still a bit much for me), and it has a nice sense of impact, presence, and rumble without overdoing it. Decently clean, detailed, and textured. It’s just odd that, for being relatively neutral in most regards, the Alpha Dog does have some extra bass. Take that as you will. If you don’t like it, you can simply adjust the tuning vents. I have since adjusted the vents for a more neutral sound, and this does work quite well.

Some smaller aspects I noticed were a very slightly cupped or honky sound to the Alpha Dog and a very slight lack of cohesiveness and clarity across the spectrum compared to some other headphones. In regards to the slight lack of clarity across the spectrum, there are other, neutral headphones out there that simply sound a bit more "hi-fi" and, well, clear compared to the Alpha Dog. As one example, and despite being a bit darker, less spacious, and more lush sounding, the ZMFxVibro has a better sense of clarity and detail across the spectrum and internal layering of the sound. I want to emphasize that this was all pretty slight on the Alpha Dog and might be difficult to notice unless one is doing direct comparisons against other headphones. Some of this also comes down to getting a good fit/seal and letting the pads warm up a bit on your head. Truthfully, there are very few, if any, headphones that sound perfect to my ears in this regard, so I don’t really think less of the Alpha Dog for it. But, when having to pick with my hard earned money, these small differences can matter in the end.

The Alpha Dog does sound fairly “open” for a closed headphone. I don’t think it’s fair to compare it to really open, airy sounding headphones, but it does very well for being closed. It does a decent job with layering and picking out subtle, low-level details. There is a nice balance between sounding not too intimate and not too distant. Plenty of presence to the sound and a decent sense of room space and reverberations.
 
Subjective Conclusion

In summary, the Alpha Dog is a bassy-neutral headphone with a slightly hard and artificial tonality that I suspect most won’t mind or notice. If anything, I could see a lot of people liking that. I just don’t think it particularly excels in any area of sound, nor does it have any faults that get in the way too much. I’d like to hear a bit more refinement, which may or may not be solvable with other front damping tweaks. However, given that it does well enough and, perhaps one of the best things about the Alpha Dog, has a few routes one can take to tune the sound to their liking, I also don’t have issues recommending it. Those willing to further experiment with other front damping schemes will likely find room for improvement. It's clear a lot of people will like the Alpha Dog quite a bit, though whether or not it’s the best, closed headphone option in this price range is something I’m not convinced of. I briefly mentioned the ZMFxVibro, and though they don't target the exact same sound signature as the AD, I do think the ZxV is more enjoyable and more refined sounding. I will have a full review of that up soon, as I know quite a few are interested in how they compare with the AD. Anyway, at the very least, the Alpha Dog's imperfections aren't too out of scope relative to something like the HE-500, which I also don't find quite perfect (not saying they do things similarly well or poorly, just that the scope is roughly on par).

Measurements and Analysis

As always, lengthy, subjective listening sessions take place before measurements. These results are also NOT comparable to other measurements out there, though you may find some similarities at times. If you are curious about how I take results or need tips on how to read these, feel free to PM me.

The frequency response results are quite telling. From above 200Hz on up, the Alpha Dog does have a fairly neutral and somewhat flat and linear sound. I do see some emphasis around 5-6KHz, at least on the left channel, and the treble quality overall isn’t the smoothest. This might somewhat explain the hard and artificial sound I heard. Subjectively, I think the treble is more filled in and cohesive sounding than measurements indicate (likely a measurement artifact due to how the AD and pads interact with my setup), though it isn’t perfectly smooth to my ears. Relative to the 1KHz point, the bass response is certainly elevated below 100Hz by roughly 5-6dB. Tyll's recent measurements of the AD also showed a bass hump, and Dan's measurements he sent me of my AD seem to confirm my results. Ideally, I’d like to see less bass and a smoother transition leading up to the 200Hz point. I think this was the root cause of the disconnected sound I heard. Channel matching is quite good overall.
 


Harmonic distortion results look OK, but not stellar (generally pretty low but quite rough looking). These results might tie in with the slight lack of spectral clarity I mentioned. The T50RP driver seems to have limitations here. There is some extra HD in the bass, but it’s not terrible. This might account for the slightly rumbly, tactile nature of the bass. The right channel exhibits some particularly odd looking harmonic distortion results. I’m not entirely sure what’s going on here, but this also isn't something I haven't seen before with other T50RP mod measurements. Either way, I’m not too worried about it so long as I don’t hear any glaring faults. Again, the T50RP driver certainly has some limitations.
 
If you weren't sure, D2 is 2nd-order harmonic distortion, D3 is third-order, and so on. You can also find calculators online to convert the dB difference to THD percentage. For example, at 1KHz or so (roughly 90dB), D2 is about -47dB to -48dB lower, which equates to roughly 0.4-0.45% THD at that spot. At 20Hz (roughly 95-96dB), D2 is about -32dB lower, which is roughly 2.5% THD at that spot.
 


 
CSDs are very clean above the 1-2KHz area or so. This is not at all surprising to me. I generally don't worry about the CSD measurements below the 1-2KHz point, though the AD does exhibit some extra resonance there relative to some other headphones I've measured. This too might account for some of the tiny lack of clarity I heard. Left channel CSD first, then right channel.
 


 
Raw measurements show a fairly consistent performing headphone. I generally trust the first and second raw takes the most, as the third and fourth takes are done in a slightly different way. However, I might actually prefer the third and fourth takes this time around, as they seemed to more closely match what I hear.
 


 
Below are some rough and quick measurements showing how the damping "dots," felt discs, and bass tuning measurably affect the sound. Since these were rough and quick takes, I'll start with a "reference" measurement of the left channel. This is with two front damping "dots" and no felt discs. You'll notice the FR matches the third raw take of the left channel above, and you might be able to extrapolate how these changes would look with a full set and averaged measurements. Keep in mind the scale of these graphs is large, like the FR/THD measurements above, and can make things look flatter or changes look smaller than they actually are.
 

 
Results with one felt damping disc (ignore that high treble ringing, should just be an artifact):
 


 
 
Results with two felt damping discs:
 


 
Results of tuning the bass vent so that is was almost closed, but not quite (enough room to breath so the sound didn't get weird or anemic). You'll notice this also affects the treble. This is with two "dots" and no felt discs.
 

 
Results of the above (tuned bass vent) but with NO dots or felt discs.
 

 
As you can see, the dots do help smooth out the treble, but they do impart other measurable characteristics to the sound that may or may not be pleasing to the ear.

Introduction
 
I found a lot to like about the OPPO PM-1, and I was very excited to give the PM-2 a chance based on impressions I had read for it. With the PM-1, the looks, build quality, and overall presentation were stellar. Though I didn’t have a personal need for it, I appreciated that it worked well from about any device, which I can’t say for a lot of other orthodynamic or high-end headphones.
 
The PM-1 had a smooth, laid-back, warm, seductive sound that was great for long, relaxing listening sessions. However, as I listened more over time, I found it to be missing something. It wasn’t the clearest, most resolving headphone on the market. Despite having good bass extension, it often sounded soft and a bit too light-footed. The treble area was a bit too rolled-off for my tastes as well, though I appreciated the fact it offered zero listening fatigue. In the end, I really wanted to like the PM-1, but it ultimately became a bit boring over time, had too constricting of a sound stage, and lacked a particular sort of finesse that many other high-end headphones offer. Despite the excellent presentation and its ability to work well from about any device, I just wasn’t sold on the price for the sound I was hearing.
 
After reading the PM-2 would target a similar sound at a much lower price, with OPPO claiming the main audible differences were due to newly developed pads, I was intrigued. As impressions started rolling in from folks I tend to trust, I became more and more eager to give them a shot. Rumor had it that the PM-2 offered a less laid-back, less constricting sound. In other words, it sounded like what I was originally looking for in the PM-1. Sure, maybe it didn’t include a fancy wooden box and used plastic and pleather instead of metal and leather on the headphone itself, but I found that to be more than a fair trade off for the reduced price.
 
So, how does the PM-2 sound, and how do they compare to some other popular headphones? I’ll get to that in a bit.
 
Presentation, Looks, Build Quality, Comfort, Etc.
 
I already mentioned that I thought the PM-1 was stellar when it came to presentation. The premium materials and beautiful box screamed “luxury” and made me want to love the headphone. Alas, it was not meant to be. I was a tad worried the PM-2’s substituted materials might not be up to par with the PM-1, but I was pleasantly surprised. Unless you can compare them side-by-side, the PM-2 still feels like the same luxurious product. The materials seem solid and feel nice, the build quality seems great, and the looks are basically as good as on the PM-1! And while they might not have the same fancy packaging, they still give the feeling of being a premium product. I also like the fabric/denim carrying case they come with.
 
The PM-1 wasn’t the most comfortable headphone I’ve ever tried. It wasn’t bad, but it could get a bit heavy on the top of my head after a while. This is a fairly common problem for me, though. With the PM-2’s materials, I get the feeling the PM-2 is not as heavy as the PM-1, and it does seem to hurt my head a bit less over time. Maybe I’m just crazy. Clamping force is not too strong either, but it’s easy to bend them to a shape that better fits your head if you have a large noggin. I think most will find the PM-2 to be a rather comfortable headphone.
 
As expected, the PM-2 works just as well as the PM-1 from a variety of devices. I even found the sound quality to be rather acceptable from my phone. While they do seem to scale with a nice dedicated, desktop DAC/amp setup, I think it’s great that these can be enjoyed around the house or on the go from about anything, even if I didn’t have a personal need for that.
 
Overall, I give the PM-2 very high marks in all of the non-sound related categories. While I do miss the PM-1’s shiny, wooden box, the PM-2 still looks and feels solid. Very nice!
 
Sound Quality
 
Was the PM-2 the improvement I was looking for over the PM-1 when it came down to sound quality? I’ll answer that right away by saying…sort of. The PM-2 comes across as less dark and less rolled-off sounding on the top end. A bit less soft and laid-back. Less constricting in the soundstage. While this seems like it would be an improvement across the board, the PM-2 does take a step or two back relative to the PM-1.
 
The PM-1 I listened to and measured had a sort of peak around the 10KHz area, and it was fairly depressed relative to the rest of the spectrum due to the rolled-off nature of the headphone. So, they were still laid-back sounding but without sounding totally veiled, as that peak helped give a sense of detail.
 
The PM-2, on the other hand, has a peak around 8KHz. To me, this is a subjectively worse spot to have a treble peak, because instead of offering extra detail, it gives the PM-2 a sort of raspy, rough, or edgy quality to the treble relative to the PM-1. There are a couple other factors that exacerbate the issue. First, the peak is narrower than the peak on the PM-1, so it sounds less cohesive and stands out more. Second, the PM-2 isn’t as subjectively rolled-off in the treble response, which again makes the treble peak more noticeable. While it generally is not a problem and won’t hurt your ears, as they’re still a laid-back headphone, it does make the treble sound relatively rough and unrefined sounding compared to the PM-1 and other headphones.
 
Whether or not someone likes or dislikes this, the PM-2 is definitely laid-back in the upper-mids and treble, roughly in the 3-7KHz range. The information here doesn’t go entirely missing, nor does the sound become a whole lot less cohesive or odd sounding because of this, but it does give them a more laid-back presentation relative to some more neutral headphones. Personally, I don’t mind this much, as it makes them much easier to listen to with harsh music and/or over long listening sessions. For example, you might notice in rock or metal that distorted guitars have less of a bite and edge to them, which isn’t always a bad thing in my mind.
 
The PM-2, much like the PM-1, also isn’t the cleanest sounding or most resolving headphone on the planet. If anything, they sound ever-so-slightly hazy and warm. I suspect some of this is due to their frequency response and some of this is due to some very specific, measurable harmonic distortion characteristics, which I’ll touch on later. That’s not to say they sound “low-fi,” because they certainly don’t. You just might notice a lack of pure clarity across the spectrum and less defined layers in the sound relative to headphones that do better in this category. The soundstage is a bit on the small side, but it doesn’t sound nearly as narrow as the PM-1 did. They’re not quite up to a reference class, if that makes sense.
 
Subjectively, I felt the PM-2 is still a bit soft sounding, like the PM-1. It could use more kick and a more dynamic sound. That said, the bass is rather balanced, fairly clean, and definitely not accentuated relative to the rest of the spectrum. It only becomes particularly noticeable when compared to headphones that have a more impactful sound, though this can often be alleviated by pairing the PM-2 with a powerful amp.
 
Now, I will say that the PM-2 often gets tonality down pretty well, they do sound fairly cohesive, and they’re a fairly enjoyable listen once you sink into them a bit. They also do very well when it comes to the midrange. I really appreciate their more laid-back nature, as it tends to suit my tastes rather well. While I do wish the treble was smoother sounding, as they are a step back from the PM-1 in this regard, and I ultimately could use slightly less laid-back upper-mids and treble, I think the PM-2 sounds pretty darn good. Not “excellent” or “reference class” in my mind, but pretty good. They do much more right than they do wrong, and what they do wrong isn’t necessarily offensive and really comes down to personal tastes in the end. I can’t say that about many headphones. At the very least, the PM-1 and PM-2 both offer a lot of encouraging signs about what OPPO might be able to do in the future.
 
From just a sound perspective, I’m not sure I’d be quite willing to spend the full retail price on the PM-2. However, when factoring in their looks, build quality, and ability to run decently from about any device, that does put them in a more positive light. Even then, I’m still not sure they’re worth the full price given all that for me, but they might be exactly what you are looking for. They do seem to fit an interesting niche in headphones, for sure.
 
Quick and Rough Sound Comparisons with Other Headphones
 
I wanted to see how the PM-2 stacked up to some other popular headphones, and just from a sound quality perspective, on a decent, dedicated desktop setup. I had the Sennheiser HD600, MrSpeakers Alpha Dog, and ZMFxVibro headphones on hand to compare with.
 
I have to admit, when only considering sound quality from a dedicated desktop setup, I found the PM-2’s sound disappointing relative to what you get from the HD600 and HD650 (only did a brief comparison with the HD650, but did do extensive comparisons with the HD600). The HD600 was immediately more engaging sounding, mostly by having a more impactful, heavier sound. The PM-2 was a bit too light-footed in comparison. However, the PM-2 did seem to have better bass quality, as the HD600 can sometimes be a bit thick sounding, primarily due to the 100Hz bump and rise in harmonic distortion down low. Subjectively, despite these traits, I still found the HD600 more enjoyable overall.
 
The HD600 also clearly demonstrates how laid-back the PM-2 is in comparison. Upper-mid and treble details shine through when listening on the HD600, making the PM-2 sound like it’s missing something. When not doing direct comparisons, this is much, much less noticeable on the PM-2. On the other hand, I actually find the HD600 to be a bit too hot and edgy in the 1-4KHz area for my ears (upper-mid to treble). In that regard, I found the PM-2 more pleasing to listen to, as I actually have to mod the HD600 a bit to lower the response in that area in order for me to listen comfortably over long listening sessions. Going beyond that, I thought the HD600 had smoother, more detailed treble than the PM-2.
 
The HD600 also had slightly better clarity across the midrange and treble spectrum. Neither of the two are particularly expansive sounding headphones. I thought the PM-2 did a bit better with macro-layering at times, though this was often a toss-up. The HD600 did clearly excel at micro-layering. For example, when listening to orchestral music, the PM-2 would sometimes sound a touch wider and better separated with large musical layers. The HD600 would do a better job enabling me to pick out individual instruments in a tightly clustered group. I also thought the HD600 had a better sense of air.
 
Now, will the HD600 do quite as well from a wide variety of sources? I don’t think so. That is one big benefit the PM-2 holds. On the other hand, I couldn’t help but be a bit disappointed with how the PM-2 sounded compared to the HD600 overall given the price differential. To be fair, given one can often find the HD600 for around $300, I’m not sure you can really find a better value when it comes to high-end headphones. The HD600 was a big surprise for me when I picked it up a couple months ago, and I can see why they’re so beloved by many. (I can’t speak for how the older Sennheiser revisions sounded.)
 
Comparing ortho-to-ortho, the PM-2 is even less similar to the Alpha Dog and ZMFxVibro. The latter two are definitely on the bass-heavy side, as they each have a bass boost below 100Hz (though are tunable). This immediately made the AD and ZxV the most powerful sounding headphones of the bunch. Personally, I preferred the middle-of-the-road HD600 approach to this in most cases.
 
The PM-2 again sounds more laid-back than the AD and ZxV, primarily in that upper-mid and treble region. I thought the ZxV struck the best balance in terms of response in this area with the PM-2 coming in as being the second most preferable here to my ears, even despite their differences. The AD sounded wider and more expansive than any of these headphones, and while it is quite neutral above the 100Hz mark, it has a slightly hard glare and artificial nature to its sound. The PM-2 had the roughest treble of the bunch. Generally, I found I preferred the ZxV and HD600 most out of the bunch, though when not doing direct comparisons, the PM-2 is definitely quite enjoyable. Again, this is from a dedicated, desktop setup.
 
Measurements and Analysis
 
After extensive listening, I took some measurements of the PM-2, and I’ll offer some frequency response comparisons as well. If you are interested in learning more about my measurement system so that you can better understand my results, PM me for more info. I do want to say that my measurements are NOT always comparable with other measurements you’ll find elsewhere. It’s best to just compare within my own setup and data. Feel free to share or re-post these graphs so long as you give credit to me.
 
Frequency response measurements indicate a nicely balanced response from 20Hz-2Khz or so. A tiny bit of extra bass warmth does appear to be evident. The dip centered around 5KHz would explain the laid-back nature I heard in the upper-mids and treble. The 8Khz peak, while mostly in line with the rest of the spectrum, does stand out by being so narrow and in an area that gives the sound a subjectively rough and raspy quality.
 

 
Distortion results are overall very good and even push the limits of what my setup can measure. The only thing worth pointing out is the 2nd-order harmonic distortion spikes in the 300-400Hz area, which are a bit odd. This might somewhat contribute to the slightly hazy quality or give a bit of extra warmth, but I doubt this is subjectively problematic or even noticeable in the end. The PM-1 exhibited the same trait.
 


 
CSD results are clean in the upper-mids and treble and indicate the PM-2 has no real issues with ringing or resonance in those areas. Don’t worry so much about how they look below 1-2KHz or so, as about every headphone I measure exhibits slow decay there (likely inherent to setup).
 


 
Raw measurements indicate a headphone that is pretty consistent with performance and doesn’t rely too much on a perfect fit and seal. With the four raw measurements on each channel, the first two and last two results for each channel are taken in slightly different ways, hence the discrepancies. While I do average these all together in the end, I personally felt the first two raw measurements on both channels best captured how the PM-2 sounded according to how I hear it subjectively.
 


 
Frequency response results compared to the HD600 are interesting. Both headphones do things I’m not crazy about. The HD600 has that 1-4KHz rise that bothers my ears, making them subjectively “hot” sounding, and the PM-2 has too large of a broad treble dip for my tastes (the narrow, sharp dip on the HD600 is considerably less audible). That said, the HD600 is subjectively much more lively, smooth, and detailed up-top and is on average more balanced sounding to my ears despite the 1-4KHz rise (this rise is fixable with EASY mods, but this review isn’t the place to discuss HD600 mods). These results also show the HD600 having a stronger response around 100Hz, which explains why they sound more impactful and lively below. (If you’re curious, I took quick measurements of the HD650, not saved, and they had a bit more bass and much less of a 1-4KHz rise…very similar to the HD600 otherwise.)
 

 
The Alpha Dog is much bass-heavier than the PM-2 in comparison, though it does have a more neutral response in the upper-mids and treble. The Alpha Dog is certainly more lively and spacious sounding. However, the Alpha Dog does have a slightly “hard” and “glaring” quality to it without felt discs in place, and that small ~6KHz bump may explain things here. I did like the laid-back nature of the PM-2 relative to the Alpha Dog for long listening sessions or with harsher music. (The treble dip on the Alpha Dog is most likely partially a measurement artifact and partially just inherent to how I measure headphones.)
 

 
Compared to the ZMFxVibro, the PM-2 is again less bass-heavy, though the PM-2 does seem to have tighter channel matching. Measurements don’t tell everything in this story. The ZxV is a more lush and powerful sounding headphone in ways that extra bass can’t always explain. The ZxV is a bit laid-back in the treble, but still less so than the PM-2, and this is evident when listening to music. The PM-2 seems to have this treble information buried a bit in music. Personally, I generally preferred the ZxV over the PM-2, as it suits my tastes quite well. (The ZxV measurements were done with one tuning vent open on each channel.)
 

 
Lastly, here are how my PM-1 (velour pads) and PM-2 (stock pads) measurements compare. I didn't have both sets on hand to compare directly from a subjective perspective, just my data, but some of this is surprising to me based on what I hear on the PM-2 and remember hearing on the PM-1. The PM-1 does show a treble peak around 10KHz vs 8KHz on the PM-2, which is more "detailed" sounding vs "raspy" sounding, and the fact that the peak on the PM-1 is broader means it sounds more cohesive with the rest of the spectrum. Some of the other difference I am not so sure about. I have heard rumors from a few different individuals that the PM-2 might actually have slightly different internal damping than the PM-1, so it might not just be pads making a difference in sound between the two.
 

 
If you are interested in additional measurements for comparison, including THD and CSD results, please feel free to PM me. I’ll have a full review up of the Alpha Dog and ZMFxVibro at a later date.
 
Oh, one last bit of information you might find interesting. I noticed the PM-2 had a better sense of detail and air if I lifted them off my head just a bit, still maintaining a seal, so that the clamping force was effectively lighter. This led me to stretch out and widen the PM-2's headband so it had a "permanent" light fit on my head. They sit very lightly on my head and over my ears now. How did that change the sound? Well, it measurably seems to have filled in that upper-mid and treble dip somewhat, and the treble response overall seems to be better balanced and smoother. And this makes sense, as having your ears closer to a driver tends to reduce the treble response, and more clamp equals closer ear-to-driver distance. This is a quick measurement, one take, of the left channel only. Compare to the left raw 1 and 2 results above for the best idea of how this sounds. Don't worry about the random THD spikes in the bass, as those are artifacts, and ignore the uglier graph.
 

 
Maybe I just have a big head, but this quick tweak is worth keeping in mind if you're in the same boat as me!
 
Conclusion
 
I think the PM-2 has a lot going for it. It wasn’t quite the big improvement over the PM-1 that I was hoping for, but it is generally a step in the right direction. They have a fairly pleasing sound, do well with tonality, and have a very good midrange response. However, as much as I like a laid-back sound, I think they could use a bit more presence in the upper-mids and treble, and the treble quality is rougher than I’d like. When compared to headphones like the HD600, Alpha Dog, and ZMFxVibro, I can’t help but feel OPPO hasn’t quite nailed the sound just yet…something is just missing that makes me think pricing is still a bit too high on the PM-2. That said, the PM-2 does have many strengths outside of pure sound quality that make me think rather positively of them. For example, if you’re looking for something that feels like a premium product, sounds pretty good in a laid-back way (not excellent, though), and works well from about any device, I wouldn’t have any issues recommending the PM-2. Even then, I think the price is a bit high, but others might consider them to be a good value. I think you could argue it both ways.
 
I really don’t like giving numeric scores, but from a sound quality perspective, I think these are a solid 7/10 (from a reference perspective, not personal taste perspective). All other areas are a solid 9/10, if not better, in my mind. While I’m hesitant to say these are quite 8/10 material when all things are considered, I suppose I’ll round up a bit in my mind and rate these at a solid 4/5 stars.

Disclaimer: I received my R3s for free under the condition I would write a review for them. Purchase price reflects their going rate on a popular online retailer at the time of the review.
 
The Brainwavz R3 is certainly an interesting IEM in a few ways, but it's the overall design, shape, and style of fit that immediately stand out. I was a little unsure what to expect from a sound perspective, but I was definitely worried these would be impossible to wear comfortably, assuming I could fit them in my ears properly at all. In the end, I was pleasantly surprised in most areas.
 
Design, Fit, Comfort, Etc.
 
Admittedly, I had no clue how to wear these at first. I spent a good part of half an hour trying to put them in my ear horizontally, which led to them continuously falling out, a lack of proper fit and seal with the tips, and the cable would just not stay behind my ear. I was almost about to write them off until I discovered they were meant to be worn in a vertical style, if that makes sense. Feeling sufficiently stupid, I put them in the right way. Ah, much better!
 
Assuming one doesn't make the same mistake I did, the R3s are...surprisingly comfortable. They are definitely on the large and heavy side, so I can't give them high marks on comfort. This also made them a bit more prone to wanting to fall out of my ears. I also can't say they really gave me too many issues, though. It's at the "good enough" level where it doesn't get in the way of how I feel about them overall. However, I do suspect some individuals might have issues getting them to fit comfortably in their ears.
 
The cable is a bit thick and unwieldy, and even after putting them in the right way, the cable would sometimes give me fits and want to jump out from behind my ears. The cables also had some sort of plastic piece on them that tended to exacerbate this issue and/or produce very mild irritation against the back of my ears. Once you get the cables where they need to be, and assuming you aren't doing anything too physically crazy, it's not too bad.
 
Sound Quality
 
I thought the R3s did a fairly good job with sound quality. They are not perfect in every way, nor are they perhaps the most balanced sounding IEMs in this price range, but they were certainly pleasing to listen to.
 
The R3s don't have particularly exaggerated bass. I actually found the bass to be rather balanced and nicely extended. They did seem to have a bit of mid-bass warmth and bloom, but this is something I often find subjectively pleasing if mild and done tastefully.
 
The R3s have a fairly good balance up through most of the midrange. I did notice a bit of depression in the very upper mids and lower treble, though not to the point where this caused an odd sound. If anything, it gave them a bit of a laid-back nature. Whether or not one finds that tasteful will come down to personal tastes.
 
Treble response is probably where the R3s are weakest. While overall fairly smooth and detailed, I did seem to notice a bit of glare and bite in a couple narrow band areas. I did not find these troublesome, as they were relatively in line with the rest of the spectrum. Out of curiosity, and after I had spent time listening, I was able to find two measurements of the R3, and it would appear these slight peaks, relative to the surrounding areas, sit around 4-5KHz and 9KHz. I believe it might be the latter that ever so slightly stood out. That said, I am generally pretty sensitive to midrange and treble issues. Since the R3 didn't give me subjective problems or sound displeasing, I suspect very few, if any, will find the treble to present any sort of problem.
 
In terms of soundstage, I thought the R3s did a fairly good job giving a sense of room space and reverberation, if not a bit on the small side. Perhaps better than what other IEMs I have tested. Clarity and detail was also pretty good across the spectrum, though they're not super resolving or detail monsters.
 
If I had to summarize the R3's sound, I'd call them decently balanced, a bit warm and laid-back, and ever so slightly bitey in the treble depending on what sort of music you're listening to. I am tempted to say they somewhat remind me of my Oppo PM-2. Similar in some characteristics, but not entirely. Overall, I'd give them fairly high marks in terms of sound quality. Definitely quite enjoyable, in my mind.
 
Summary
 
I wouldn't have any issues recommending the R3s with some caveats. The thick and unwieldy cable is my biggest annoyance, but with some patience, you can make it work. The design of the IEM itself is unorthodox and might lead to some fit and comfort issues on some individuals, but I will say they weren't too bad in this area and did much better than I expected (once I figured them out!). From a sound quality perspective, I thought the R3s were decently balanced and quite enjoyable to listen to, though not perfect. It is only because of the cable and unorthodox design that I give the R3 a 3.5/5. Otherwise, I'd easily give them a 4/5, which means I'd recommend them (BTW, anything higher than 4/5 for me is very rare). 

Disclaimer: I was contacted by a Brainwavz representative to try out a free pair of S5 IEMs under the condition I would write a review for them. I received them in mid July and have sampled them over the past two weeks or so. I listed the purchase price as their current listing of $99. I have tried them from my dedicated, desktop headphone system and from my phone.
 
Overview - Build Quality, Looks, Comfort, Etc.
 
The Brainwavz S5 IEM has a decent amount going for it at face value. They look good, feel solid, are comfortable, and they include a nice set of accessories with plenty of tips to choose from and a carrying case. I usually have troubles getting IEMs to fit and seal right with my ears, but the S5 doesn't give me these problems for some reason. That's a plus. Aside from sound, which I'll get to in a second, these headphones do well across the board. I'll refrain from elaborating on those aspects more, to avoid wasting your valuable time, and move on to the sound quality.
 
Sound Quality
 
This is where I was nearly immediately disappointed with the S5. Coming from headphones or speakers with a known good, fairly balanced response (i.e. HD600, HE-500, Paradox, Mad Dog, Alpha Dog, VSonic GR07...you name it), the S5 sounds overly bassy, has missing midrange information, and has artificial, thin, and uneven sounding treble.
 
To break it down a bit further, they are certainly bass heavy, but thankfully they aren't totally bloated or mushy sounding. They do extend well below and have plenty of impact, but it's simply overbearing on the rest of the sound spectrum. The treble also has some peaky spots, giving the headphone an overall sort of U-shaped sound signature. I'm usually OK with a bit of a "fun" sound signature and am able to appreciate non-neutral products with ease, but the S5 trends towards simply sounding weird and "low-fi." They have a very distinct cupped sound to them.
 
The midrange subjectively has a suckout in the 1-3KHz area. This can sometimes help a headphone sound more relaxed, but it's a bit much in this case and offset by problems elsewhere in the audible spectrum. I noticed a broad peak around the 4-5KHz area and two sharp peaks around 9KHz and 12Khz or so. The areas in between these peaks similarly come off as troughs (i.e. missing information). The S5 does extend fairly well into the upper treble but doesn't sound airy due to the booming bass.
 
Overall, this gives the S5 a very booming and yet sharp sound. Fat and thin at the same time. Treble comes through as thin and artificial and makes cymbals sound wrong. The midrange and treble unevenness causes male vocals to lack proper body and a sense of breath, and they get pushed back into the mix more than they should. Guitars tend to take a backseat and lose their sense of body, though certain areas of detail are highlighted due to peaked areas. Bass drums and bass guitars dominate the scene along with the peaky mid and treble areas and any voice, instrument, or noise that occupies the peaky areas of the frequency spectrum. Lastly, the headphones are so-so in terms of resolving power. Some details come through OK, but a similar amount of details get smeared together. Again, I suspect this is due to the uneven nature of the frequency response.
 
At the very least, I didn't find them fatiguing or hard to listen to. I have no doubt some will like this sort of tuning, but it is simply not for me and far off a reference target. But, given they're an IEM I can actually wear comfortably without fit and seal issues, I might be able to find a use for them. I know some have said they got a better sound with the S5 by having a less-than-perfect seal, but A) that defeats the purpose for me with an IEM and B) they just fall out of my ears without a perfect fit and seal anyway.
 
They look good and seem like a good deal at around $100, but I just don't think the sound quality is there on the S5. You might like them, but I can't say that I do.