Andover PM-50 Review - Misunderstanding Neutral

Review written by Andrew Park (@Resolve)

Headphones provided for review by Andover Audio

Introduction

The recently released Andover PM-50 is a planar magnetic headphone that comes in at $499. This means that it has entered into a very competitive segment of the market that includes the HiFiMAN Sundara, the Sennheiser HD660s, the Audeze LCD-1, all the way up to the DCA Aeon Flow RT. If Andover Audio’s website marketing material is to be believed, the PM-50 is a headphone that could have a 'reference' sound signature. There are numerous testimonials suggesting that this would be a good headphone for mixing/mastering. As we’ll see with this review, however, that’s unfortunately not the case. In many ways the PM-50 is a shining example of how the term ‘flat’ or ‘neutral’ is far too commonly misunderstood when it comes to headphones - whether by prospective customers, audio media, and perhaps in this case even by the manufacturers.

Specs

  • Headphone Style: Over-Ear
  • Driver type: Planar Magnetic
  • Enclosure: Genuine Walnut Hardwood
  • Ear-Cushions: Two Sets
  • Cable: Removable / Upgradable
  • Headphone Impedance Rating: 32 ohms
  • Driver Sensitivity: 102dB/1mW

Sources

Build, Design & Comfort

The PM-50 has gone for a minimalistic design style and aesthetic, and this is something I really appreciate. There’s a sleek wood accent to the cups that feel sturdy - like I don’t have to worry about how carefully I put them down on the table. The headband and cup articulation is sparse for materials, and that’s likely to help keep the weight down as well. And so while it doesn’t look and feel as premium as its price tag might indicate, this is a design style I can get behind. There’s also a bit of cup swivel, which I find is a must for headphones these days in order to get it to fit properly for a wide range of head shapes.

Unfortunately, this is where the praise stops. The initial two sets of pads that came with the PM-50 were far too small even for normal ear sizes - so much so that Andover has sent out larger earpads because they likely got similar feedback. The good news is that the larger ear pads fit my ears much better, making the PM-50 overall a very comfortable headphone. The bad news, is that no matter which ear pads you use, the PM-50 is not a good sounding headphone to me.

Performance

The PM-50 is a modern planar magnetic headphone, meaning that it uses a diaphragm with a conductive trace on it that’s immersed in a magnetic field. This is what creates the pistonic motion for the diaphragm, ultimately moving the air to create sound. This is different from traditional dynamic (moving coil) transducers that have a voicecoil behind a cone or dome shaped diaphragm. You can read more about differences in driver type and how this corresponds to sonic characteristics here.

In this case, the PM-50’s transducers are overall quite small compared to other planar magnetic headphones, coming in at only 50mm. But, in my experience, transducer size isn’t necessarily a limitation.

Detail Retrieval

The PM-50 has some decent midrange detail retrieval, with a good sense of clarity and texture to it, however the mid-treble detail (between 7-9khz) suffers from a bit of grain and haze. This isn’t helped by the frequency response, which we will get to. Upper treble detail and air is also quite good, however the bass detail leaves quite a bit to be desired. So for example, when you hear a bass tone from an upright double bass, you get more single-tone definition than the microdetail and textural qualities that exist down low as well.

Speed & Dynamics

The PM-50 is appropriately fast for its price tag, largely helped by being a planar magnetic headphone. I often find that planar magnetic headphones have a certain tightness to them, almost like a kind of ‘plucked’ character. The initial leading edge has a good sense of immediacy and snap to it, however the dynamics overall suffer quite a bit. I find this to be common with modern lighter planars (as opposed to the much larger and heavier designs like the Audeze LCD-2). For the PM-50, this means I don’t get any sense of punch or slam to the music. At this price, it’s tough to find a planar magnetic headphone that has this quality, but surprisingly the HiFiMAN Sundara does do a better job of this quality than the PM-50.

Soundstage & Imaging

I find the soundstage on the PM-50 to be slightly more spacious than the HD6XX, but really not by much. It doesn’t have the ‘three blob’ issue, where you only get left, right and center - it’s a bit more filled in than that - but the overall depth and distance is a few steps behind the HiFiMAN Sundara, and quite a bit behind the Beyerdynamic DT-1990 Pro.

Timbre

For material-related timbre, I find the PM-50 to have a typical planar timbre that some find less natural sounding than many dynamic driver headphones, but I don’t mind it all that much. I find this quality to be most noticeable in the bass, where the bass tones are well-defined, but at the cost of natural decay and reverberation that comes across with instruments being represented.

Frequency response related timbre is a bigger issue in my mind, and the PM-50 sounds very unnatural, almost as if listening to music from inside a fishbowl. And to dive into that, let’s talk about how the PM-50 measures next.

Frequency Response & Tonality

The following is how the Andover PM-50 measures on the GRAS 43AG standardized measurement system relative to the combined Harman target curve (Harman 2013 bass but Harman 2018 mids and treble). For reference, the Harman 2018 bass is substantially elevated - far too much for what I think most audiophiles would consider appropriate, even if some bass heads may like it, so I prefer to use the more modest 2013 bass shelf. In any case, these are raw measurements, and that means that they don’t take the dotted target curve as their compensation. This instead shows the raw measurement relative to the target that would otherwise be normalized in compensated measurements. I’ve also added the compensated measurements at the bottom so you can see how it looks when we assume this target is a flat line (i.e. where the headphone is supposed to measure like a flat line).

How do you read this? The dotted black line is the target (how we might want it to measure), and the colored line is how the headphone in question measures. Effectively, this shows how significantly the headphone’s frequency response deviates from the target.

PM-50 with small pads vs Harman Combined

PM-50 with medium pads vs Harman Combined

PM-50 with large pads vs Harman Combined

So what are we looking at here? What does all of this mean? I'm usually the first person to say that measurements aren't the whole story, and there's a lot more to it than that. But for all of the emphasis around the PM-50 being a ‘neutral’ or ‘flat’ measuring headphone, technically they’re not wrong - that is, if humans didn’t have ears. And in some ways if we didn’t have ears, the PM-50 would probably sound pretty good.

The problem is that the physical ear amplifies certain frequencies and resonances, and this is what the brain expects to hear (the brain compensates for this amplification). Essentially, we want headphones to measure with a rise beginning at around 1.5khz just like the dotted line in these graphs shows. This is what’s called “pinna gain”, and for the PM-50, for some of these pads, it actually has negative pinna gain.

This is a huge problem for how the headphone sounds. In short, this is an extremely muted and muffled sounding headphone that’s beyond ‘dark’. Remember that the brain expects to hear an elevation similar to that of the dotted line starting from around 1.5khz, coming back down around 9-10khz because this range is where the physical shape of our ears amplify sound. Now I should stress that to some, the PM-50’s dark tuning might be in line with their preferences - it’s not uncommon to find warm or dark sounding headphones. But it has to be said that this is emphatically one of the furthest from ‘neutral’ sounding or ‘flat’ measuring headphones I’ve ever come across at any price, and prospective buyers should be aware of this.

Here is how the PM-50 measures on a compensated graph (where it should measure flat, or close to it), and we can see that it’s significantly subdued in the upper mids and treble. Essentially, the Andover PM-50 is all lower mids and upper treble.

Note that while the target curve being used in these measurements is a consumer preference curve (as opposed to a traditional diffuse field target), the 2018 Harman target is one of the most relaxed options for upper mids and treble, meaning that the deviations shown here are even somewhat on the charitable side.

Now apart from the negative pinna gain from 2-5khz, there are also a number of other problems with the Andover PM-50. The first is that there’s a noticeable bass roll-off below 70hz. This means that while the upper bass is present (and even slightly elevated), the sub-bass is almost non-existent. Moreover, while the upper treble presence is actually quite good, there’s a kind of ‘shimmer’ quality that’s imparted by the 9khz peak. Now you might be thinking, this region is below the target, shouldn’t it measure more closely to it? Generally the answer is yes, but at 9khz, a peak like this causes this strange ethereal shimmering character that obscures other elements in the mix.

In my mind, the main issue with the PM-50 isn’t so much that it deviates so strongly from the target. A lot of people enjoy warm or dark headphones (I even personally own some). The problem, as I see it, is that a fundamental misunderstanding or confusion about how the ear amplifies certain frequencies has led to exactly the opposite of what a 'reference' sound signature should be. The PM-50 completely ignores all aspects of ear-related gain factors, and as a result it sounds dark, muted, and muffled to me. And just to reiterate, this may be exactly the type of tuning some people are looking for, but this really shouldn’t be billed as having a ‘reference’ or 'neutral' sound signature.

EQ

Given how dark the Andover PM-50 measures, I really think it’s worth diving into some EQ to try to see how it sounds with appropriate ear-related upper midrange and treble gain added in. 

Here are some fairly conservative EQ settings that bring the response much closer to the target. Note that I don’t match it perfectly, since I do this mostly by ear.

With this EQ applied, the PM-50 sounds a lot better to me, however the treble grain and lack of bass detail persists regardless - at least to my ear. Moreover, the somewhat ethereal sounding treble with the 9khz peak is still a problem for me. I’ve gone back and forth on how to fix this and ultimately it requires a particularly narrow filter, and this is something I generally don’t recommend doing for most people. So while this EQ profile does improve things, it’s still not quite to my taste in the treble. At least the midrange detail still comes through well.

Comparisons

HiFiMAN Sundara ($350)

While the PM-50 may have similar midrange detail to the Sundara, and maybe even slightly better (I’m still on the fence about that because it may just be in the lower mids), the overall tonality for the Sundara is far superior to my ear. The Sundara is a headphone that both sounds and measures exceptionally well. Moreover, the Sundara also has better punch and slam, a more spacious presentation, and overall better treble and bass detail. Importantly, there’s also no unnatural shimmer quality to the Sundara, and it simply sounds far more natural. I think most people will find that the Sundara is a much more ‘neutral’ sounding headphone, and it comes in at a significantly lower price tag. Just keep in mind that you need an amp for it - although I’d suggest that regardless.

Sennheiser HD660s ($499)

Similar to the Sundara, the HD660s is a much more agreeable sounding headphone to me. While the Andover PM-50 does have a superior soundstage, and I find its midrange detail may also be slightly better than that of the HD660s, everything else about the HD660s sounds better to my ear. It’s a much more natural presentation, with also a more appropriate frequency response. Both the Sundara and HD660s are far more neutral and simply better sounding headphones than the PM-50.

Conclusion

The Andover PM-50 is not the worst sounding headphone I’ve heard, but it’s certainly one of them. And that’s a shame, because there are certain aspects to it that could be enjoyable. I like the comfort with the large pads (the ones that Andover sent me afterwards), I like that it’s a fairly lightweight planar, it’s got a good looking cup design, and it has decent midrange detail.

Unfortunately, I see the PM-50 as a missed opportunity due to its failure to appropriately include the ear-related elevation in its frequency response for the mids and treble, leading to an extremely dark and muffled sounding experience. Add to that a few other shortcomings relative to its competition, and it lands the PM-50 at the bottom of my list. The one consideration that’s worth keeping in mind is that the PM-50 may be a worthy modding headphone for anyone looking to get into that scene. It’s easy to take apart with a simple screwdriver. 

But apart from that, under no circumstances can I recommend the Andover PM-50 for anyone looking for a neutral sounding reference headphone - especially with pro audio applications in mind. For those who are really into dark sounding headphones, then maybe that’s a different story. But even then, at $499 I would encourage you to try before you buy.

 Andrew Park (@Resolve)

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