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.