The Hzsound Heart Mirror's (HM's) tuning seemed like it'd be promising as a replacement of the Moondrop SSR, which I consider a benchmark budget IEM due to its bright-neutral tuning, flaws and all. There are a fair number of positive reviews of the HM as well, so I figured why not buy it?

I'm about to tell you why you shouldn't buy this IEM.



Build

Others have already commented on the build and accessories, so I will repeat what stands out to me. The earphones feel nice in the hand and do look good. The cable is okay. Kind of memory prone, but I had a replacement copper cable to go with it. It's a bit heavy but fortunately I recently got the QX-Over and the medium tips for those worked well with them.

Comfort

The IEMs fit my ear well enough. A bit large in the nozzle but the right eartips largely fix that.

Sound Quality

Tonality

The tonality here is essentially that of a leaner and brighter SSR. I like me some treble, but the bright tonality here is only good for listening for somewhere between a half-hour to an hour before fatigue sets in.

Lows: I'm not a basshead, so when I say that the bass response is minimal, take that as you will. At best, it supports the track, but on average there's either barely any bass or no bass at all. Low-end emphasized electronic music sounds analog and fuzzy, like with meganeko's "Cybergrind", due to the meager bass response. Cellos and lower percussion like toms or kick drums come across rather decently when they go low, like on the TAMUSIC or Tokyo Active NEETs track, but they lack fullness and sound flat.

Mids: The HM will often veer into sounding too thin for male vocals to sound tonally correct since the fundamental tones are barely audible, compared to the harmonics in the rest of the mix. This lends to a somewhat limp sound from the likes of Joakim and Chester Bennington. Female vocals sound a bit shrill but do come across rather clearly, as a whole. Similarly, stringed instruments like violins and especially cellos sound somewhat weightless in the lower fundamental tones...

Treble: ...but after a certain frequency, they come across clearly. Too clearly, as a matter of fact. Yes, acoustic tracks sound crispy and symphony orchestra and female vocals, but the bright presentation is not pleasant to listen to. If there is sibilance in your recording, it will come across in spades, such as with track "The Creator". It feels like there's too much air or something. With the Prisma Audio Azul IEM, my reference for a neutral IEM, I get a certain sense of fullness due to the air frequencies being only a bit above neutral, at worst. Here on the Heart Mirror, that same fullness is exaggerated and bloated to the point where it's a rough listen, as opposed to a smooth listen. The music feels like it's pressing into my eyeballs and the back of my head with the Heart Mirror. Blinding, really, which is apt for an IEM with "Mirror" in its name.

Technicalities

I've heard oddly tuned IEMs which I could sort of enjoy due to their technicalities making up for it. Here, the HM has below average technicalities. *Far* below average. Admittedly, the bright tuning lends the overall presentation the veneer of resolution and detail, and if you wanted to listen to something bright while working, it'll sound detailed enough. But if you give even a single iota of attention to the sounds coming into your ear, you might find something lacking. I certainly did, and it ruined my enjoyment with them.

I cannot isolate or separate instrument and voice lines with this IEM. There's no layering, either. I hear a violin coming from the lef--but I cannot isolate it from the others. I hear Joakim of Sabaton somewhere in the cente--but there's a fog separating me and the music, with little details poking in and out of it. Only on tracks with a vocalist and a guitar was there any sense of separation.

This is related the way this IEM fails to handle detail retrieval, e.g. reproduce the transients associated with an instrument in the recording. It's very smoothed over. For example, throughout the song K. by Cigarettes after Sex, I can hear the initial pluck of guitars or tug of cellos but there's not much follow-through. The vocalist in that same song uses vocal fry as part of her singing style, and there are other IEMs in this price range that can reproduce the roughness of her voice, but the HM smooths that roughness over and smothers how she sounds. And in the Tokyo Active NEETs track at around 20 seconds, the trumpets have very little of the flutter and roughness one should hear from them.

The soundstage depth is somewhere inbetween zero and negative. The mental window I have of the recorded performance is strongly fogged up and is pushed into the back of my skull. This severely impacts the imaging, which is the worst form of three-blob I've yet to experience on any IEM. The middle-blob is especially smeary and imprecise with my reference playlist and songs outside of it. This is likely due, in part, to the aforementioned sonic presentation and soundstage depth.

Altogether, the technicalities are so bad that I could not imagine any sort of scenery while listening to this. This is the minimum requirement I ask of any IEM, and it failed on that front. I would always be conscious of the fact that I'm listening to something poorly recorded and have to constantly think about how meager the presentation is here. If we tally up the subpar stage depth, detail retrieval, and imaging, you get the most 2D presentation of music I've ever experienced. Truth be told, I've not yet listened to an Etymotic ER-series IEM, but I can easily imagine that this must be how 2D their soundstage is. One might call the soundstage as flat as a mirror.

A Comment on Sources

Some people claim that this IEM is source-picky, e.g. that a certain synergy is needed in order to make these IEMs shine. In my experience, no amount of amp-rolling, tip-rolling, or cable-rolling will save this IEM's sonic presentation. I've used a copper cable to ostensibly add warmth (it sounded the same as the stock cable). I've used wide-bore and narrow-bore tips, to similarly awful effect. The sources I used were as follows:

• ddhifi TC35B 2021 dongle out of a Pixel 4a
• Qudelix-5K
• Shanling M3X
• ifi Zen DAC
• ifi Zen CAN
• THX AAA 789 on Gain 1, 2, and 3
• xDuoo MT-602 (with Bellari Audio tube pre-amp and aftermarket Mullard tube) connected to M3X

Using the 789 made it barely cleaner and wider in soundstage as I ratcheted the gain switch up. Using tubes or the ddhifi dongle barely added warmth and low-end. Using the ifi Zen CAN ensured the soundstage was never negative and perhaps added a minute amount of soundstage depth. Ultimately, the Heart Mirror's sonic presentation was frustrating across all sources.

A No-Contest Comparison

The SSR stands heads and shoulders above the Heart Mirror. Imaging, staging size, detail retrieval, and separation are good enough on its own with the SSR, and put the HM to shame in these regards. I do wish the SSR was a bit brighter, but overall its tonality is a smoother, more enjoyable listen that is better balanced for all kinds of music. The SSR is the better sub-50 USD neutral reference IEM between the two. It is so easy to listen to my reference playlist with the SSR, and with the Heart Mirror, it is agonizing to do the same. The Heart Mirror has been claimed to punch above its price bracket, but it can't even punch down the SSR, in terms of price alone.

Conclusion

If one wants a bright sound to listen to music while they work, maybe this IEM could work for you. For me, I prefer a warmer tonality in that context. The tuning here makes me think it's meant to be for critical listening, but it's so hard for me to imagine the contents of the music and interpret them with the Heart Mirror. Its sonic presentation continues to annoy me on every song I throw at it. Instead, the tonality is fatiguing, and the technicalities are all but lacking on the bare minimum. The Heart Mirror is a bad parody of the SSR, and for my purposes, is an overall failure of a neutral IEM. Stay away from it.

Rating: 1/5.

Reference playlist: