Apos Caspian: Passion For Sound's Go-To Headphone Choice

Note: This article is based upon the article "Apos Caspian Headphone Review - Groovy, baby!” made by Passion for Sound on his YouTube channel. It’s printed here in partnership with SoundNews. The review was originally posted on November 23rd, 2021. It is presented here in full.


Hey, folks. Welcome to another Passion for Sound audio review. Today, we’re looking at the Apos Caspian headphones. This is a headphone that’s come about from a collaboration between Apos (an audio retailer), Sandu from SoundNews (a reviewer and headphone audio enthusiast), and also Kennerton Audio (a headphone manufacturer).

The Caspian is a $499 USD dynamic driver headphone that’s also available from Apos bundled with their very own Apos Flow Cable. The cable that comes with the Caspian is quite good. I’ll cover that in a moment. Before we get there, though, I do want to talk briefly about the design of the headphones themselves, the packaging, and accessories. 


When you buy the Caspians, they come in a really simple cardboard box, and that’s fine by me. Packaging isn’t a big deal, in my opinion, when it comes to headphones. They also come with this strange leather case. Now, I say strange because it looks more like an old-fashioned kind of camera bag for a big old DLSR-type camera. It really is a little bit cumbersome, and it’s also soft, so I don’t see it providing much protection for the headphones. In my opinion, it would have been better if they’d either left it out or come up with a hard case design if they thought it was necessary. Having said that, the Caspian is an open-back headphone, so I don’t really see a huge need for a portable case. Most people that I know don’t transport their open back headphones around with them because they’re not really good for portable use. So I would have preferred to see this left out and maybe some other accessories added in, or the cost reduced, but it’s not a big deal–just a little thing I thought I’d flag.

Moving on from that, you also get the cable here, which, as I mentioned before, is quite a nice starting point cable, so there’s no need to upgrade to the Apos Flow, but there are a couple of benefits should you want to update to the Apos Flow. Starting off, the cable’s got a couple of nice mini-XLR plugs that go into the headphones themselves, and then you’ve also got on the other end a nice solid 6.3mm connector. All the connectors feel really good. The wire split feels really solid as well, so all in all it’s a really nice cable. It’s quite thick and heavy. Some people will like that, some people not so much.

I have no issues with the stock cable whatsoever, but Apos sent me the Flow as part of my reviewer bundle, and I have to say that there are some benefits with using the Flow. Firstly, you can get it balanced. Mine came with a 4-pin XLR plug. Secondly, it’s a little bit lighter and more supple. Thirdly, there is a very minor sonic improvement going from the stock cable to the Flow. It’s not a reason on its own I would recommend spending a hundred dollars extra on the Flow, but if you like the idea of running balanced and having a slightly lighter, more supple cable, I do think the Flow’s worthwhile. 

Design & Specs

With all that out of the way, let’s start talking about the headphones themselves. The Caspians are a fairly traditional design of headphone. There’s nothing too fancy or flash here, but they’re nicely made. They look good whilst also looking fairly subtle.

The cups themselves are made out of oak, so you’ve got a nice dark timbre finish here. And then you’ve got a black metal grille here that gives the ventilation to make these an open-back whilst also providing the Apos logo. But it’s done subtly and tastefully.

I do quite like that the headband itself is pretty basic. It’s not a special headband. You’ve got this really simple, fairly flat piece of printed metal that connects to a fairly utilitarian leather-clad headband. There’s a decent amount of squish in the headband, so that’s kind of nice. But at the same time, it’s nothing special, and I’m not suggesting it should be. These are a $500 US headphone, not a $1,000 or $2,000 US dollar headphone. To me, they feel about right for the price.

On the inside of the cups, we’ve got ourselves a nice chunky opening and some nice thick leather padding here. So, all in all, everything’s good from a design, functionality, and comfort point of view. But it’s also very utilitarian. There’s nothing flashy. There’s nothing that stands out about these, and that’s completely fine.

The final point I want to mention is that, on the front of each cup here, you’ve also got a mini-XLR socket. I mentioned that when we talked about the cables, but what’s key here is that they’re pointing out of the front of the headphone, so when you put these on your head, the cable actually comes forward a little bit before it drapes down, and it makes for a very, very comfortable setup, so there’s absolutely nothing to complain about with the Caspians, in terms of comfort.

In terms of looks, they’re fairly demure. They’re fairly serious-looking. But a lot of people are going to like the fact that they’re very subtle. The finish on the timber is nice. I would probably have preferred to see something more satin, rather than gloss, but it’s a really, really minor preference. It’s not a reason to buy or not buy the Caspians.

On the inside of the headphones, we’ve got a pair of 50mm graphene-coated drivers, and what that means, theoretically, is that you’ve got a rigid, stable-style driver that should move really effectively to produce all the frequencies you want without too much distortion or breakup.

As you’ll hear shortly, it certainly is producing what I think is a pretty good sound. Before we talk about the sound, though, I just want to finish off the design piece by mentioning that these are a 33Ω headphone with 115dB sensitivity. In other words, they’re easy to drive. You can run them off a portable source. You can run them off a desktop source, no problems at all. 

Sound Quality

I want to start off by saying bravo for not following the Harman Target curve–not that there’s anything wrong with the Harman Target curve, but it’s not the be all end all. I think our hobby is sometimes hindered by too much alignment with that target curve, and whilst it can produce some wonderful-sounding headphones, it could also result in us not having much variation and diversity in the different headphones available. So I love seeing a headphone like this come out where they’ve completely disregarded the Harman Curve and produced a wonderful but different-sounding headphone as a result.

Having said that, it sounds wonderful. I should go on to say that this is a very rich and warm-sounding headphone. So, straight away, there are going to be some of you that will not like this, and I think that’s fine.

I love the fact that this is unashamedly a headphone directed towards bass lovers. It’s got this great big 40-60Hz boost down in the lower end, which gives it a subwoofer-like presence, but that’s nicely pulled back before it gets too high up in the bass and prevents the headphone from coming across too flabby and slow and loose. But it is absolutely still a warm, rich, and bassy-sounding can. I do personally find that the bass is just a little bit too much sometimes. But having said that, it does help the Caspians to be a lot of fun and a very rhythmic and groovy-sounding headphone. I don’t mean that in the 70s or 60s term “groovy”. I mean that it picks up the groove of a track. It helps the rhythm and the drive to come through because of that extra bass emphasis. They’re great fun. They’re really enjoyable, but they’re definitely not for everybody.

So let’s talk through the sound a bit more. I’ve already mentioned that it’s got a 40-60Hz type of bass boost, and that does mean that the extension goes all the way down right into the sub-regions. Interestingly, though, when you talk about bass weight (i.e. how much presence and punch it has at certain frequencies), it does vary a bit because it’s got such a strong peak at 40-60Hz–depending on the recordings you’re listening to. If the emphasis in that recording is higher up in the bass, maybe it’s mid-bass emphasis from the recording, you will find that these can be a little bit variable in my listening. Sometimes, it had a bit too much boost when the track had a lot of information in that 40-60Hz range. And then, at other times, it sounded a bit more balanced, as things were a little bit more shifted up the bass range. So there is a little inconsistency in the way that these deliver bass. It’s not a big deal, but it is worth taking note of.

Personally, I think they should have aimed for a slightly flatter overall bass response. I do like the idea of having a lift at the bass, but I think the lift maybe went just a little bit too far and has produced a slightly peaky bass. Now, it may sound strange that I’m calling the bass peaky, but my point is that it emphasizes a fairly narrow band of frequencies, and I understand why they’ve done that, but I think maybe they’ve gone just a little bit too far, and it has made the headphone a tiny bit inconsistent. It’s not bad, by any stretch, but I do think there was room for improvement.

Moving up in the frequency range, I’ve already mentioned that the bass is pulled back nicely through the upper bass and mid-bass areas, so there’s not a sense of flabbiness or slowness, despite still being rich and full. As we move into the mid-range, that same trend continues. Things are pretty well-managed. Vocals come across with a great sense of weight and presence and richness to the vocals, but without going too far.

The only thing I would say will be a negative for some people, with the Caspians, when we’re talking about vocals and mid-range presentation, is that they do lack a little bit of air in female vocals. So if that’s really important to you, if you like the breathiness and the texture in a female vocal, the Caspians probably aren’t so great. But if you love a nice, rich, creamy vocal that’s not overly thick or way, way too lush, but definitely enhanced, then I do think the Caspians could be a really nice choice.

While we’re speaking mid-range, I did find that there were just a few instruments here and there, depending on the recording, where the lush rich sound from the mid-range of the Caspians did occasionally push them just a touch too far, so that was just a slight drawback for me–that occasionally the tonality was every so slightly off, but it was very slight, and not a reason to not buy the Caspians if you like everything else that I’m describing here.

As you can probably imagine from me talking about the general tonal response of these, the treble is quite smooth. It’s never harsh or sibilant, but it does have surprisingly good extension. The treble does continue all the way up without dropping away too much, and it gives the Caspians a decent amount of treble energy and detail. That said, it’s always going to get overshadowed by the bass boost at the other end. So don’t buy these if you’re into sparkly detailed treble, but at the same time don’t get turned off thinking they’ve got no treble just because they’re a rich warm headphone. It’s actually quite a nicely balanced overall tonal response with the one exception of having slightly too much boost in that 40-60Hz range.

As a result of the bass emphasis with the Caspians, the overall sense of space isn’t exceptional, but it’s certainly not bad. Increased bass in a headphone is always going to have a tendency to reduce the amount of space available in the sound stage, and that’s certainly true with the Caspians. So there’s a good sense of width in the sound stage. There’s not particularly much depth. It’s quite two-dimensional, but the general sense of separation of sounds is completely acceptable. I wouldn’t say it’s class-leading. I wouldn’t say it’s excellent. But it’s certainly not negative. It’s just average and okay and, as I said before, that’s probably always going to be the case when you’re getting a bass-oriented headphone. As a result, the Caspian is a fairly intimate listen. You’ll find that sounds that should be layered in depth will tend to sound like they’re all coming from the same space. But instruments that are separated in the left to the right field will have a sense of space between them. So keep that in mind.

If depth and a massive sound stage are important to you, the Caspians probably aren’t the best choice. But if you’re happy with a rich, lush, engaging, and foot-tapping type of sound with the cost of having a little bit less sense of space, and a little bit less sense of separation, then the Caspians are still worth looking at. To help put that into context, in just a moment we’re going to look at a couple of comparisons.

Before we do that, though, I want to sum up what I’ve heard from the Caspian so far, and that is to say that I think they’re a great example of a rich, warm, bass-oriented headphone that’s not completely rolled off and mushy in the treble. But if it was me tuning these, I would be pulling down that sub-bass boost by just a few dB, maybe two, maybe three dB. If these were a home theater setup, I’d be going over to the subwoofer and pulling the levels down on that a little bit. That’s the kind of adjustment that it needs. It’s just a little bit too forceful in that sub-bass region for some tracks. 

Caspian vs Sundara

The first comparison I wanted to do was the HiFiMAN Sundara. Now, technically, the HiFiMAN Sundara have a recommended list price of $499 USD, making them exactly the same as the Caspians. Realistically, they often sell for much less than that, but I still think they’re a good comparison point, because a lot of people know, understand, and love the Sundara.

One of my test tracks, while comparing the two, was “Doom and Gloom” by the Rolling Stones. On this track, the Sundara come across a lot drier in the upper mid-range. Things sound more textured but also a little bit grainier because it is drier. I’m not saying if that’s better or worse, it’s just a different presentation.

The Caspians are all about smoothness and creaminess, whereas the Sundara are probably being a bit more revealing. As a result, it’s easy to listen to the Caspian at higher volumes and really get into the groove of the music. As I’ve already mentioned, “Groovy, Baby!”, but some people will find themselves wanting more of the details that the Sundara can provide. Things like guitars definitely have more attack and sense of clarity from the Sundara, so it’s definitely a trade-off between whether you want the neutrality and the balance in the tonal signature of something like Sundara or whether you want the pure foot-tapping, relaxed and easy fun of the Caspians. Now, I say relaxed. They’re not a particularly relaxing headphone to listen to. My point being when I say relaxed that they’re not forcing details at you. There is detail there, but they’re not pushing it down your throat. Instead, the energy and the excitement of the Caspians is all coming from the bass.

The other thing that Sundara does, because of its more balanced tonality, is it does provide a much better sense of space, both in terms of depth and width. In the sound stage again, I’m not saying if that’s better or worse. It’s all going to depend on your preferences.

While listening specifically to “Doom and Gloom”, one of the other things that I really noticed was the hi-hat sounds. From the Sundaras, the hi-hat was cleaner and more present in the overall mix. When I switched back to the Caspians, the hi-hat was pulled way back in the max, and what was much more evident was the bass and the vocals, and I bring that up because it’s a good summary of the difference between these two. The Caspian is all about bass, mid-range vocals, richness–all those things. Whereas, the Sundara is a more balanced overall tonality and therefore is going to present more of the overall musical picture. Again, it’s up to you which of these you prefer.

I certainly find the Caspians to be a lot of fun, but I definitely don’t find them natural or neutral at all. Another way I might describe it is that the Caspians are a very macro experience. They’re not really inviting you into the music so much as just letting you take in the entire musical performance in its most rhythmic sense. If you want to go more micro, if you want to hear all the individual instruments and the textures and the sounds, that’s where something like the Sundara is definitely the better choice.

And so, if I had to choose only one of these, the Caspian or the Sundara, I probably would choose the Sundara, because I think it’s a better all-around headphone. But if you’re in the position where you can have two headphones, maybe one’s a bit more reference and one is pure fun, the Caspian is absolutely a great option and could be a wonderful pairing for those of you with the Sundara. You can have the Sundara for its accuracy, its transparency, and also it being a planar. And then you can have a fun, easy-to-drive dynamic driver headphone sitting alongside it for those times you just want to tap your foot. 

Caspian vs Poseidon

Before we wrap things up, let’s do one more comparison, and this time it’s with the Harmonicdyne Zeus. Now, I specifically chose the Poseidon because it’s another rich and warm-sounding headphone that’s also been marketed as having this amazing sub-bass presence, which, as I covered in my review of it, it really doesn’t. But I thought it would be a good comparison to put the two side-by-side.

Playing “Lonely Stranger” by Eric Claptop, flipping back and forth between the two, the Poseidon actually came across as sounding a bit boxy and nasal after I came from the Caspians. And the reason for that is that despite being heavily bass-oriented, the Caspian is actually a better overall-balanced sound signature. What I mean by that is it transitions fairly smoothly from the bass all the way down into the treble, whereas the Poseidon has more peaks and troughs within its signature that results in an interesting and enjoyable sound in the case of the Poseidon. But certainly the Caspian does come across as more balanced because it doesn’t have as many peaks and troughs. On the flip side, though, the Poseidon is able to create a greater sense of space by pushing the mid-range back a bit. The mid-range on the Caspians, as I’ve already talked about, is very emphasized because of its weight and its richness. And that’s a part of why it sounds so intimate and closed-in–not overly closed-in but certainly comparatively closed-in compared to the Poseidon. And so the two of them have a very different presentation.

The Poseidon is definitely the better choice if you value a wider and deeper sound stage, but at the same time it does so at the expense of the deep, deep sub-bass presence that the Caspian has. Interestingly, I really expected to prefer the Poseidons on a track like “Lonely Stranger” because it’s largely acoustic. It’s not reliant on bass. I expected the Poseidons to give me that sense of space and openness and a better general experience, but I found myself preferring the Caspians. And it all comes back to the smoother transition from bass through treble, and, therefore, a more balanced overall sound.

So, on this one, I actually prefer the Caspians, but because they’re such interesting headphones, both of them, I wanted to give them a second track to see how they fared. For the second track, I landed on “Don’t Go to Strangers” by Joni Mitchell. This track has some orchestral arrangement as a backing to the vocals, and on the Poseidon it’s a much grander experience. Hearing that orchestral arrangement, the sense of clarity and space that comes from the Poseidons really helps to open up the orchestra and give you a better sense of scale and prevents it from all kind of sounding like one big sound coming at you. The same characteristics that made the Poseidon sound comparatively nasal and boxy on “Lonely Stranger” now help to bring a sense of texture and clarity to the vocals and the orchestra in “Don’t Go to Strangers.” It makes the Poseidon the more enjoyable headphone on this particular track. The Caspians are still very enjoyable on the track, and their emphasis on vocals makes it a really intimate and vocal-focused listening sessions, which can be a lot of fun, and I thoroughly enjoyed them. But I do feel like the Poseidons had the edge by being just a little bit more open and clear-sounding. 


Where this all left me was that I feel like the Caspians would be absolutely stellar if they just pulled back the bass a little bit and maybe brought just a tiny bit of extra emphasis in the right pockets of the treble or the upper-mids.

As it is, the Caspians are still great, and in fact, I’d say by way of conclusion that if you’re in the market for something different, something fun, engaging, foot-tapping, if you want a headphone that’s going to excel in any genre that needs that 40-60Hz bass range, the Caspians are a great choice.

I think they’re sturdy. They feel well-made, even if they’ve got some off-the-shelf parts. They don’t come across as feeling like a thrown-together, half-baked idea. They feel properly made. They feel sturdy, solid. They come with a nice cable or a great upgrade cable option.

I do think they’re a recommendable headphone. To put that recommendation into some context, I’m kind of looking at these now as the replacement for my Meze Empyrean. This is not to say for a second that they’re anywhere near the performance of the Empyreans, but they’re giving me that fun factor that I do lack sometimes from the Meze Elites and any other headphone in my collection.

If I just want to put on a track and rock away to it, the Caspians are absolutely a headphone I’ll be reaching for. And so if you’re looking for a headphone that rocks, that grooves, if you’re into EDM, electronica, hip-hop, rap, anything that needs a really strong, chunky bass presentation, you should absolutely check out the Caspians. They’re a really well-balanced example of a rich, warm headphone. The bass does go a bit too fast sometimes, but that’s really easy to tweak with a little bit of EQ if you’re so inclined.