Introduction
Every year, new trends emerge in the in-ear monitor market, and in the first part of 2023, we witnessed several brands delving into the world of earphones with switches that allow for sound signature customization. Today, I bring you how KZ sought to introduce an IEM with adjustable tunings to the market at an affordable price of less than $30 USD. Let's check KZ D-FI out!
Video Review here
If you wish to read this review in spanish, click here
Disclaimers:

• KZ kindly sent me this product to provide an honest review of this model. You can find the KZ D-FI here: https://s.click.aliexpress.com/e/_ol5SwPd (Aliexpress), https://www.kztws.com/products/kz-d-fi?variant=44493358661883 (Official Website)
• Analysis over 5 days - Sessions of approximately 2 to 4 hours
• All music is lossless (Qobuz > 16-bit - 44.1kHz)
• Gear Used: TempoTec Sonata HD PRO (most of the time) / IFI Zen Air Can (AMP) + Fiio E10K (DAC) (to test how it scaled with amplification)

Unboxing, Build & Comfort

Despite costing nearly double the price of the ZVX, they come in practically the same box, only with a different image. Inside, you can find the pair of IEMs, 7 pairs of tips and the cable.





Starting with the D-FI, these come with the new dual magnetic circuit dynamic driver with dual cavity from KZ. Their housing is made of polished shiny metal and has a slightly triangular shape. On the top, you can find different switches that, along with this tool, allow you to adjust the bass frequencies to change the sound signature. Finally, on the sides, we see the QDC-type 2-pin connectors. I have to tip my hat to the build quality of these earphones.




According to their website, the cable is described as a "professional" cable plated with high-purity silver. The truth is, it's the typical cheap KZ cable with QDC 2-pin connectors.

The quantity of ear tips was a surprise coming from the ZVX. The D-FI comes with 6 different pairs of wide-bore silicone tips and a pair of foam tips. The foam tips are size M, just so you know. Personally, they didn't fit me very comfortably, so I decided to use the regular silicone tips (size M).

The comfort of these headphones is better than average in my experience. They are slightly heavier due to their construction, but it didn't bother me when using them for several hours, and I never had to readjust them after inserting them correctly into the ear canal. With the right tips, the isolation provided by the D-FI is more than decent and will be useful for users who need to use them in noisy environments


Sound Description

This is the difficult part because KZ claims that the D-FI can offer up to 16 different tunings. What the company states is true, but the problem lies in the fact that certain configurations have sound signatures that are very similar to others, as the bass frequencies only increase or decrease by 1dB, without resulting in a significant change. That's why I focused on 3 specific configurations (D = switch facing down, U = switch facing up): a very neutral one (DDDU) that reminds me of the HZSound Heart Mirror but with better bass and less sibilance, the one which had the most subbass available to test this frequency range (UUUD), and my preferred tuning, which, to my ears, sounds the most balanced (DDUU).

I decided to test these 3 configurations with a variety of songs that are quite different one from the other, so you can get a good idea of what you can expect thanks to the versatility of D-FI's tuning.

General Summary



Credits: Ian Fann

• DDDU: similar tuning to IEF Neutral, where the switches decrease the bass to allow the mids and highs to stand out. Very good for genres like heavy metal, soul pop, or others where the vocals are prominent.
• UUUD: The tuning that highlights the sub-bass the most. It doesn't reach basshead levels, and I found it useful for making EDM and Dubstep songs more “fun”.
• DDUU: The tuning where I found the best balance across all frequencies. It may not seem like much, but those 1-2dB difference from UUUD are noticeable, and they make a difference. Sub-bass with good extension and character, along with bass that doesn't disrupt the transition to the midrange. This is the tuning that best adapts to the different genres where I tested these IEMs.

Songs
"Aces High" - Iron Maiden (Live After Death)

DDDU: By reducing the amount of bass, the presence of the guitars and the lead singer increases (at the same volume level). The bass doesn't suddenly disappear and can still be heard, but it's overshadowed by the aforementioned sounds (vocals and instruments forward). I also feel that the cymbals have taken on a more significant role. The constant percussion that accompanies the entire song becomes more prominent and sounds clearer in this configuration. Lastly, the backing vocalists accompanying Bruce are better heard here too. I really liked it for heavy metal as it gives an extra sense of texture to each note played by the electric guitars.

UUUD: The guitars and lead vocals almost become equal to the bassist in volume, and at certain parts, the bass even seems like the star of the song. Around the 2:10 mark, the guitar solos begin, and supposedly the bass only plays on the background, but it is much more emphasized with this configuration, perhaps intruding a bit too much on the solo. It's not something I love, but it's a strange yet fun way to listen to this song that I've heard so many times.

DDUU: The most accurate configuration of the three tested. It doesn't overemphasize anything. You can always hear the bass and guitars clearly, with the guitars never interfering with each other and standing out on each side when they should. There is proper articulation during Bruce Dickinson's vocals along with his accompanying guitarists. The cymbals never sound aggressive to my ears. The bass is present and follows with good sense of presence, but never intruding into the higher frequencies.


"Miss You" - Adele

DDDU: It's evident that Adele is the protagonist of the song. The tambourines can still be heard clearly, although I lose a bit of the presence that the drums have during the chorus. Bright details like cymbals or small bells are well distinguishable during the chorus, but the female voice takes the most prominence in the mix.

UUUD: Adele's voice is much more in the background. This is not a song with a lot of bass, but the drums manage to be very close (and sometimes overpowering) to Adele's voice in terms of volume (especially during the chorus where it seems like the lead singer is distant for this reason). The details in the high frequencies are not lost too much but remain slightly more hidden.

DDUU: In this configuration, I find the balanced harmony that I expect from this song: Adele's voice has excellent clarity during the chorus, and it sounds smooth and silky. Meanwhile, the drums are positioned slightly behind her, providing punch that distinguishes their sound. The small bells in these moments are perceived gently without getting lost if one concentrates a bit on their location.


"Like Wooh Wooh" - Rnbstylerz

DDDU: In this tuning, it's uncertain which sounds should stand out since the majority of them occupy the bass and subbass frequencies. As a result, the "claps" and the bass frequencies closer to the midrange (midbass) try to stand out or match the volume level at which the deeper bass is playing.

UUUD: The sub-bass takes an even more authoritative character during the song, sounding visceral, and bassline’s presence occupies most of our attention. Despite this, and to my surprise, I never lost those "claps" that follow the drop (compared to other mentioned songs where this tuning concealed other frequencies).

DDUU: There isn't much difference from the previous configuration since "Like Wooh Wooh" is a song primarily based on subbass frequencies. The tuning sounds slightly less "fun" than UUUD configuration because the subbass has a bit less strength, allowing for better control of this frequency and bringing out the synthetic sounds of the drop.


"Luck be a Lady" - Frank Sinatra (Live at Carnegie Hall)

DDDU: It's beautiful to hear Sinatra stand out in this song. The reverberation in the hall is clear, and he is the most present on that stage. His voice sounds organic and somewhat "forward" in the mix. Without being too far behind, I can hear the trumpeters who shine in the "strong" parts of the chorus and in a solo they perform around the 4:00 mark. The cymbals also stand out without being overly bright. I really enjoyed this tuning for this type of songs.

UUUD: Going from the previous configuration to this one is like listening to a different song. Upon replaying it, I can notice that a bassist emerges who was very hidden in the other tuning and now becomes more present. The voice and trumpets remain stronger since this bass is in the background, but their volume has diminished. The cymbals undergo something similar, but in my experience, they don't lose as much character. I didn't find it to be an ideal tuning for this type of song; the significant boost in bass attenuates the mids too much, and the song sounds hollow.

DDUU: In comparison to the previous two, this tuning comes across as inoffensive. The trumpets are much less aggressive than in DDDU, and I can hear the bassist without any issues. However, the reverberations presented in DDDU are not as crisp here, and I slightly prefer the greater authority that the latter gives to Sinatra. For this reason, I favor the DDDU tuning for this particular song (although overall, I believe that DDUU has a better balance in its frequencies).


Winter: I. Allegro non Molto" - Vivaldi (performed by Fabio Biondi)

DDDU: The principal violinist stands out in this configuration, but only slightly more than usual. There is a nice sensation with the plucking of each string. Overall, the violins, despite their authority, do not become extremely bright and are enjoyable for long listening sessions. On the other hand, the double basses and cellos lose some impact during their playback.

UUUD: The double basses have much more weight. The violins (including the principal violinist) lose some presence. When the principal violin plays solo, it sounds a bit muted, and the cellos and double basses emerge, remaining just slightly behind it.

DDUU: The violins have a more faithful reproduction, with a more natural timbre to my ears compared to DDDU. However, I feel that they lack a bit more weight in each note. The double basses and cellos don't get lost in the mix.


"Don't You Worry Child" - Swedish House Mafia

DDDU: The bass is set far back in this song (in which is required to shine like in most EDM songs). The lead singer's voice is clear and occupies the forefront of the song along with the cymbals and synthetic sounds. The guitar accompanying the singer sounds a bit strange to me, with notes having an artificial/metallic tinge.

UUUD: In the build-up to the drop, it's evident how enhanced the subbass is. When the drop plays, it seems like two different melodies are playing: on one hand, we have the cheerful synthetic sounds, and at the same level but "separated" we have strong sub-bass/bass notes marking the rhythm with their characteristic thump. As I explain, these don't sound like they're coming from different places but rather feel like they lack harmony between them. Particularly with this EDM song, I didn't enjoy the heavy bass as it alters the sound balance too much.

DDUU: Of the three configurations, this one sounds the most natural (particularly in this song, I can tell how it "should sound" since it has been my favorite song since 2015 and still is. I must have played it hundreds of times). There's good weight in each note of the guitar accompanying John Martin before the drop. During the drop, there's an excellent balance between the bass and mid frequencies that sound together. In my opinion, it demonstrates that this configuration is the most "accurate" for a user seeking a tuning with sub-bass with decent extension, bass with sufficient presence and texture but allowing the mids to have their important role in the sound with enough details for $35 USD.


Soundstage, Imaging & Details
Testing live performances from the album I most commonly listen to "Live After Death", I noticed a decent soundstage in several configurations. The width of the stage was adequate, but I found it a bit compressed in terms of depth.

Regarding imaging, the D-FI didn't surpass the average in this price range. I encountered a few songs where it was challenging to locate and separate certain sounds, as I mentioned with Adele, where I had to concentrate to find those bells. However, overall, they perform adequately.

The level of detail the D-FI brings out is comparable to other IEMs below $50 USD. I can appreciate certain details, even though its tuning aims to avoid sibilance and doesn't overly emphasize the treble based on my experience.


Conclusion



Just as not everything that glitters is gold, not everything KZ releases to the market is average, and the D-FI is proof of that. To this day, this model is available at a very good price, around $20 to $25 USD. If you're a user looking for IEMs that can provide different sound signatures for enjoying your music, along with excellent build quality and a coherent driver, I sincerely recommend D-FI.

Introduction

The KZ ZVX is a recent budget model released by the company "Knowledge Zenith" (abbreviated as KZ) which implements their newest 10mm dual cavity DD and aims to compete in the sub $20 USD IEM market, with an estimated price of $18 USD.

Video Review here

If you wish to read this review in spanish, click here

Disclaimers:

• KZ kindly sent me this product to make an unbiased review. You can check the KZ ZVX here: https://s.click.aliexpress.com/e/_opu0tVH (Aliexpress), https://www.kztws.com/products/kz-zvx?variant=44402385617147 (Official Website)
• I use stock accessories in my reviews to form a fair opinion about the product
• Review based in 2-4hs listening sessions each day across 5 days

A “little” inconvenience

This one won't start with my typical review format of "Unboxing, Build & Comfort," "Frequency Response Description" and "Subjective Sound Description." You may be wondering why, and here's the explanation.



I have tried other KZ products like the DQ6, which also came with a cheap cable but never caused me any issues. And here we have the ZVX, trying to compete with other cheap headphones in this range but neglecting an important matter: quality control.

The first day I started analyzing the sound of these headphones, I began by listening to Billie Eilish and then switched to Heavy Metal music like Iron Maiden and In Flames. EVERYTHING SOUNDED DIFFERENT. The guitars sounded distant, and the cymbals even more so in songs like "State of Slow Decay" and "Rime of the Ancient Mariner"; the bass overpowered all the other frequencies in songs like "All Good Girls Go to Hell." My initial feeling was one of distress because I imagined that the drivers were defective, and there was nothing I could do about it. A few minutes later, after testing the ZVX on different devices to make sure it wasn't my phone or PC's fault, I remembered that I had a 2-pin cable from my HZSound Heart Mirror that was compatible with my old DQ6, which incidentally had the same QDC connector as the ZVX. That's when I had the brilliant idea to give it a try…

BINGO, the drivers weren’t defective, it was the cable! All the songs returned to "normal." I haven't stated my verdict yet, but it's already a significant negative point that I wasn’t able to use the included cable to evaluate the performance of the ZVX.

Now, I'll return to a more structured writing format.


Unboxing, Build & Comfort

The ZVX comes in the typical small KZ box, which is to be expected for $18 USD. We can find the cable and 3 pairs of foam tips included.




The IEMs themselves have a surprisingly solid build considering their market value. Comparing them to the 7HZ Salnotes Zero that I recently reviewed, these feel much more premium with their full electroplated metal construction with small brand engravings. On the top and to the side, there is a protruding QDC-type connector. The ZVX is available in both black and silver colors.



The selection of tips felt a bit strange to me: only 3 pairs of foam tips. I don't think it's a bad idea to include them in the package, but it's odd that they are the only available tip selection with the ZVX. Something that crosses my mind is the longevity they will have since silicone tips tend to last a very long time if maintained occasionally. On the other hand, foam rubber is practically impossible to clean and usually has a limited lifespan.



The cable is a 2-pin type compatible with QDC connectors. I believe you already know my opinion about it...

The comfort is adequate once inserted into the ear canal. I didn't have to readjust them more than once or twice. However, the seal they provide to the ear is not exceptional. Using the smaller foam rubber tips, I achieved only average isolation.


Sound description (+ some comparisons with 7HZ Salnotes Zero)



It's no coincidence that I mentioned the Zero earlier. In addition to being in a very similar price range, both IEMs have a very similar tuning, as can be seen in the measurements.


Credits: Paul Wasabii

Bass

To test the bass, I listened to "Buried" by IMANU. This, like other songs in the EDM genre, pairs well with the amount of bass provided by the ZVX. The bass has a good sense of impact both in the drop and carrying the song's rhythm.

Continuing with "Gimme That Bounce" by Mau P, once again, the more visceral bass of these headphones stands out in this genre. The subbass also has good presence and authority here. Increasing the volume a bit makes the subbass feel chest-rattling and can be heard with good clarity.

In the two mentioned EDM songs, the Zero doesn't stand out as much in my opinion, which is why I see the ZVX as a good option for people seeking a tuning similar to the Zero but with more emphasis on bass.



Mids

In "Vivere" by Bocceli, I found a proper balance between the female and male vocals, with neither one standing out more than the other. However, the more pronounced V-shaped tuning places the vocals slightly behind in the song, alongside the cymbals and bass. Despite this, I had no trouble distinguishing each sound individually.

"Bury a Friend" by Billie Eilish emphasizes the mentioned point a bit more, as the sub-bass/bass and synthetic sounds overpower Billie's vocals at the 2:40 mark, causing her to lose the spotlight during the chorus.

After my listening sessions with the ZVX, I do miss the more present mids that the 7HZ provides with its more balanced/neutral tuning.



Treble

Listening to "Somebody To Love" by Queen, I noticed a good articulation between Freddie and his backing vocalists. They all sound correct. The point I want to emphasize here relies at the end of the song, where the drum cymbals are played multiple times. There, I found the treble peaks to create an extra sense of detail at the cost of some slightly piercing/sibilant passages.

In this aspect, I believe the KZ team has succeeded. I appreciate this additional detail that these IEMs offer me in genres like classical music, where I seek to analyze each particular sound more meticulously. I found this aspect particularly useful in "Swan Lake, Op. 20, TH. 12 / Act I: No. 2 Valse (Corps de Ballet)" by the Boston Symphony Orchestra, where I felt that the bells had greater clarity.



Soundstage & Imaging

"Hallowed Be Thy Name" by Iron Maiden (Live at Long Beach Arena), the bass, guitars, drums, and lead vocalist's voice are sounds that are easily distinguishable from each other and not difficult to locate on the stage (good imaging).

However, the tuning lacks air. In live concerts, I noticed little separation between the guitars on the left/right and the lead vocalist in the center. Overall, these headphones create a fairly compact three-dimensional soundstage and are the most "intimate" in-ears I have tried so far. The soundstage has small width (side-to-side distance) and depth (front-to-back distance).

I found that the Zeros have a slightly worse imaging but much better spatiality in terms of width and depth, making them more enjoyable for live performances.



Conclusion



Why not less than 3 stars if the cable comes faulty from the factory? Why not more than 3 stars if some aspects were better than the 7HZ Salnotes Zero, which you gave 5 stars? It's simple, the ZVX is an $18 USD pair of IEMs, so buying a new cable doesn't represent a significant expense. Having said that, I don't find it acceptable for the included cable to have these kinds of issues when I have already tried other products in this price range that didn't have any faults.

I can recommend the ZVX for its sonic characteristics to people looking for IEMs with impactful bass and a bit better treble definition compared to the Zeros. However, the overall package of the product left me a bit disappointed.

Introduction
The current market for "budget" IEMs (under $200 USD) is saturated with single dynamic driver earphones, where some models don't present significant differences from others. However, the implementation of affordable IEMs with planar magnetic drivers has been on the rise lately. Today, I will analyze the LETSHUOER S12 PRO, a pair of planar magnetic earphones with a modular cable and exceptional construction, available for $135 USD.

Video Review here

If you wish to read this review in spanish, click here

Disclaimers

• The product was provided by LETSHUOER for an unbiased review - You can find the S12 PRO here: https://letshuoer.net/products/lets...-ear-monitors-for-audiopiles-and-music-lovers
• Review based in 2-4hs listening sessions each day across 6 days
• All music is lossless (Qobuz > 16bit - 44.1kHz).
• Gear Used: IFI Zen Air Can (AMP) + Fiio E10K (DAC) / TempoTec Sonata HD PRO (dongle)

Unboxing, Build & Comfort

The box is of considerable size and weight, but once opened, it is understood why its dimensions are that large. Inside, the first thing we find is a catalog of their products. Just below that, we can see the bright blue IEMs, along with 3 pairs of foam tips. Finally, at the bottom, there is a faux leather case that contains a modular* cable of very high quality for the price, 3 pairs of wide-bore silicone tips, 3 pairs of narrow-bore tips, and some paperwork such as the manual and product certification.

*modular: allows for interchangeable terminations between 2.5/3.5/4.4mm.




If I were to see these earphones for the first time without knowing the price, I would easily say they could be worth more than $200 USD. The housing is designed with an aluminum alloy which feels very solid to the touch and has well-hidden vents that relieve pressure build up in the ear canal. The driver used in the S12 PRO is a 14.8mm single sided planar magnetic driver.


Summary of how the driver works: This type of driver works through a thin metal diaphragm with an array of embedded "wires." On each side of the diaphragm are magnets with opposite polarities. When connected, the current passing through the wires generates a magnetic field that interacts with the permanent magnetic fields of both magnets, creating undulating movement in the diaphragm thus producing sound.

The included modular cable is of very good quality. It is built with silver-plated monocrystalline copper and has 4 cores, each consisting of 98 strands. Its connector type is 0.78mm 2-pin with interchangeable terminations for 2.5, 3.5, and 4.4mm. One criticism I have in this regard is that the cable is heavier than average (by quite a bit, in my opinion), and it can be uncomfortable during long sessions. Also, the plastic cable earguides that go over the ears are uncomfortable, and I would have preferred if they were not included.



The number of silicone and foam tips is a very positive aspect (9 pairs in total!). I mostly used my favorite ones, which are the wide-bore tips, but the foam tips feel of good quality for those who need isolation.



The comfort of the S12 PRO was just okay for me: as I mentioned before, the plastic guides are not of my preference and the heavy cable doesn't help that much either. However, when they are properly positioned in the outer ear, they seal decently (it's not the best seal, but it provides enough isolation), and I had to readjust them only a few times. It's worth noting that they protrude a bit, so I wouldn't recommend using them while lying down.

One small aspect I'm going to add in this case is the driving power needed for the S12 PRO. It's known that planar magnetic drivers can be difficult to amplify, but that's not the case with this LETSHUOER set. When I used them with my smartphone (directly into 3.5mm input), I only needed to increase the volume up to 50% to reach a comfortable level when listening to music.

Frequency response description

Credits: https://aftersound.squig.link/

• Slight V-shaped signature
• Subbass and bass above neutral
• Mid frequencies with a more subdued character but without losing prominence
• Treble somewhat lively but peaky and with good extension

Subjective sound description

Bass
Despite what the measurements indicate, I found the a sub-bass and bass near neutral. The bass have good definition but lack impact for basshead users.

In songs like "Paris" by M|O|O|N (Hotline Miami soundtrack), the sub-bass has a strong presence, and you can feel it “deep within you” throughout the entire song as it takes the spotlight. The same happens in "Xanny" by Billie Eilish, where during the chorus, those sub-bass frequencies can be felt “down to the bones”.

On the other hand, in "Back Around" by Tiesto, I experienced what I mentioned earlier: the impact of the bass during the drop leaves me wanting 1-2dB more for EDM songs. However, this reference tuning is particularly good for other genres as we'll see next.


Mids
As someone who listens to various Heavy Metal/Rock artists and different orchestras, I consider myself familiar with the sound of string instruments. In the case of "Meet Your Maker" by In Flames, the electric guitars have a good sense of texture in each note and avoid being piercing to the ear.

Switching genres, in "Yellow" from Coldplay's concert in Buenos Aires 2017, from minute 2 to 2:56, the electric guitar accompanies the song very gently, only to reappear seconds later. In this chaotic harmony, where instruments and the lead singer's voice come together, you can clearly distinguish each individual sound. Chris Martin's voice has a natural timbre to my ears, and both female and male voices have good weight in the region.

Lastly, in "Nessun dorma!" performed by Pavarotti, the Italian's voice is out of this world. There is particularly good harmony between him and the orchestra (choristers, violins, horns, trumpets, piano, etc.).


Treble
Again, the graph shows quite pronounced peaks in the 2.5 kHz and 8 kHz regions, yet the previous song by In Flames with continuous cymbal splashes did not come across as piercing at all.

Furthermore, in classical music such as Tchaikovsky's "Swan Lake" performed by the Boston Symphony Orchestra and Mozart's "Divertimento in F Major, K. 138" performed by the Quatuor Van Kuijk, I noticed that these IEMs are not super analytical or bright. In fact, for those seeking to gather every tiny detail in their music, they may find themselves wanting a bit more from the S12 PRO.


Soundstage & Imaging
In the previously described Coldplay song "Yellow," I could perceive a sense of distance between the audience and the band. However, to my ears, the soundstage is wider than it is tall and deep. There is good distinction of distance between the sides, but not as much towards the front and back.

But here's where it gets exciting: the imaging capability is spectacular. In Avicii's "Waiting for Love," the single-sided planar magnetic driver manages to separate the different layers of the song's introduction. If I were to describe them from "top to bottom" what I hear is: first, Avicii's vocals above everything else, in the middle the rhythmic sound of the piano keys, and then below or in the background, the drums with their kicks and cymbals accompanying the song. Both instruments and vocals disappear during the build-up to the drop and are replaced by synthetic sounds. When the drop hits, these instruments reappear in the same "layers". The drums only play their cymbals while the song’s bass is carried by a synthesizer that is introduced at this moment.

This description showcases the capabilities of this type of driver, providing a precise image that allows the listener to clearly differentiate which instruments are being reproduced and effortlessly separate them from one another.

Conclusion

Unfortunately, I cannot speak about the improvements LETSHUOER made to this IEM compared to the first S12 as I did not have the opportunity to try that model. However, based on my experience and comparing the presentations of the S12 and S12 PRO, it is evident that it was not a simple tuning change. Adding a modular cable of even better quality than its predecessor (128 strands vs. 392 strands) and maintaining the same solid construction makes those extra $15 USD worth it. In terms of sound, I had some criticisms but there are more positive aspects that I can highlight about these IEMs, and I must say they are a great way to enter the world of planar magnetic IEMs.

Introduction
The acclaimed 7HZ Salnotes Zero are IEMs with a single dynamic driver per side that shook the IEM market a few months ago, receiving support from top reviewers and being highly recommended by many users for their excellent performance at a more than acceptable price ($20 USD).
Video Review here
If you wish to read this review in spanish, click here
Unboxing, Build and Comfort
The box is simple but expected in this price segment. Like in most cases, upon opening it, we find the pair of headphones, and underneath them, two small bags: one with the 2 pin 0.78mm cable and another with 5 extra pairs of silicone tips.



The construction of the IEM itself feels cheap. The 10mm driver with a metal composite diaphragm is protected by a plastic molded housing and a metal faceplate with the brand and model inscriptions. A positive aspect of this type of construction is the variety of colors offered for this model, with a total of 6 options: white, black, light blue, red, pink, and orange.



Moving on to the cable, it is quite good for the price. It has good flexibility, doesn't tangle easily, and has a straight 3.5mm connector, relieving the tension at the cable termination point compared to "L-shaped" connectors. As negative points for this cable, it is slightly microphonic when it rubs against clothing, and the plastic ear guides may be uncomfortable for some.



Regarding the silicone tips, I was surprised by the quantity included (6 pairs, counting the ones already on the IEMs). Some of these are "wide bore" tips like the orange ones (which retain better bass and treble frequencies), while others have a narrow bore like the light blue ones (which reduce treble frequencies without affecting the bass, resulting in increased bass emphasis).

Lastly, the comfort of these headphones was excellent from day one. I always used them with the small-sized (S) orange tips, and both the shape of the IEM and those tips contributed to an exceptional seal in my outer ear. They are so lightweight and comfortable that I can wear them for hours without needing to readjust them. They are a great option for anyone needing peace in noisy environments.

Frequency response description

Credits: crinacle.com

• Deep sub-bass extension and well-presented bass
• Smooth transition from bass to the mids
• Mid frequencies following almost strictly the Harman target
• Laid back but airy treble with good extension

Subjective sound description

Bass
The sub-bass has a lot of authority, as demonstrated in songs like "Xanny" by Billie Eilish and "Hot In It" by Tiesto. The sensation of "rumble" in these and other songs is very good, and the sub-bass can be felt in the chest.

On the other hand, the bass frequencies (>50-60 Hz to 200 Hz) are slightly lacking for my taste, as evidenced in EDM songs like "Follow" by Martin Garrix. However, this prevents the bass frequencies from "bothering" the mid frequencies and allows for a smooth transition between them.

Mids
I listened to several different singers to have a good reference for this frequency range. Freddie Mercury, Billie Eilish, Adele, and Calamaro - all these artists sounded correct here.

Both male and female voices are reproduced naturally with more than adequate presence, although female voices have a slightly more authoritative presence, as I heard in "Vivere" where Bocceli sings together with Gerardina Trovato.

The articulation between the different instruments and voices occupying this range is very good, without any interference or "disturbance" between them at any moment.

Treble
In general, the high frequencies may leave something to be desired for those who prefer a brighter and more detailed tuning. However, this is a very positive aspect for long listening sessions, where this IEM will reproduce the entire music library with exceptional musicality. In "Black Magic" by Slayer (Live Undead), the drummer's cymbal in the first 30 seconds is never offensive to the ear and has good presence. In "Revelations" by Iron Maiden, the variety of cymbals played by the drummer during the guitar solos have a gentle presence without being aggressive or overly bright.

Timbre
The timbre of these headphones is something that other companies should take note of. I understand that it's not a bold tuning as it follows the Harman curve, but the instruments are so well represented that despite not being the best IEM in terms of resolution/detail, they can be compared to others that are far above their price range thanks to the excellent execution of timbre. All the instruments in Vivaldi's "Winter: Allegro non Molto" - performed by Fabio Biondi - are excellently distinguished from each other, from the lead violinist to the cellos and double bass accompanying the rest of the violins.

Soundstage & Imaging
As mentioned earlier in the frequency response description, the soundstage or spatiality of the sound is above average. Songs like Iron Maiden's "The Great Unknown" and Queen's "Bicycle Race" reveal that these headphones have a wide soundstage that can be deep when needed. In the latter mentioned song, a well-crafted three-dimensional scene is created, placing all the backing vocals and drums behind Freddie, with one of the cymbals having a distinct presence located behind and to the right during the chorus.

Regarding imaging, this is one of the few weak points I see in the Zeros. In Calamaro's "Alta Suciedad," it's difficult for me to discern between the guitars playing on the right and left channels. The same occurs during the introduction of the Iron Maiden song mentioned in the previous paragraph.

7HZ Salnotes Zero vs KZ DQ6
I decided to make a brief comparison between these two models as they are both in the same price range internationally and in Argentina (Price: $20 USD for any of them)

Credits: crinacle.com

• The DQ6 has more punch and rumble due to a more pronounced elevation in the bass frequencies. They are comparable in the sub-bass range, with the Zero having slightly better extension in this range.
• The more "correct" transition between the bass and mids makes vocals and instruments sound a bit more natural on the 7HZ compared to the DQ6.
• The high frequencies are two opposite poles in my experience: the DQ6 has bright highs at times that help create a sense of detail but may have some small sibilance, while the Zero has more relaxed/dark highs that are not as detailed but contribute to its musicality.
• In terms of timbre, there is no competition; the 7HZ Zero has achieved a better tuning in this aspect.

Conclusion
It is quite obvious that this is a product easy to recommend: good comfort, impeccable tuning for the price, a good amount of accessories of respectable quality for $20 USD. The few negative points I mentioned during my analysis clearly are not enough to lower this product from the pedestal it deserves to be on.

Introduction
The Superlux HD 668b where my first “non gamer” headphones as I always wanted to step up my audio gear and at the time (2020) it was the best over ear headphone I could afford.

If you wish to read this review in spanish, click here

First Impressions (2020)
My last “gamer” headphones were the Steelseries Arctis 3. Both headphones feature a V-shaped signature where the bass and treble are a little bit boosted. However, when I switched from the SteelSeries to the Superlux, I instantly noticed that the sound opened. This is because in the Arctis 3, the mids seemed so lost beneath the rest of the frequencies that any voice or instrument in this range sounded lacking in body. Unfortunately, I sold the Arctis 3 several years ago, so I cannot make a direct comparison, but trust me, the improvement was significant.

Unboxing, Build and Comfort
For $35, the unboxing experience is very good. The headphones come in a decent cardboard box and come with a good variety of accessories: 2 cables (a 1 and 3 meters long), a 3.5mm to 6.35mm adapter and a carrying bag.

The build is mainly based on plastic except for the metal headband. Despite this, they feel like solid headphones that won't break from a few falls to the floor. Also, this amount of plastic makes them extremely lightweight, which is a plus if they are going to be worn for several hours. Clearly, this build is similar to several AKG models, and the headband is very similar to the renowned Audio Technica R70x. The earcup and headband cushions are made of pleather.

A particular thing about the 668b is a 3.5mm connector hanging from the left earcup to connect the headphones cable. Many people mention that this is a clear weak point in the construction and can break at any time. In my 4/5 years of use (not continuous but regular), they have not suffered any problems in this area, but I thought it was good to mention it so it is taken into account.

Comfortwise, this is the worst aspect of these headphones objectively. If you are a person who is used to the low clamping force headphones that float on your head, you will have a bad time with this pair. One piece of good news is that after two weeks of use and letting them rest with the headband open in some box or support, the clamping loosens considerably.


The earpads are also a problematic point for these headphones. They are very shallow, so it is very likely that the ears will touch the fabric covering the driver. However, according to what I searched (but have not yet tried), the earpads compatible with AKG K240 can fit in the 668b earcups, relieving the discomfort that the pleather and shallow earpads may cause.

Frequency response description

Credits: DIY-Audio-Heaven

• V shaped sound signature but sounds well balanced with bass notes not bleeding into other frequencies.
• Boosted mid bass but with good control avoiding interference with midrange sounds.
• Neutral midrange which makes female and male vocals sound natural and articulate.
• Boosted highs that are sibilant most of the times (problematic for mid and higher volume level listeners). However, they provide great clarity.
• Great extension in the treble giving a sense of "air" and spaciousness in music.

Subjective sound description


Bass
There is an early sub-bass roll-off, so these headphones do not extend that well in that range. However, there is a good amount of mid bass, it has punch shown on sounds like drums and on EDM song basslines. In "Vivere" in particular, the large number of instruments in the song can be heard clearly, with a very pleasant bass guitar which is always present behind the vocals without interfering.

"7th Dimension" (Koan Sound) has good bass rumble. The good quantity and quality of bass highlights electronic music, giving it a "fun" character. The 668b handles passages with a wide variety of synthetic sounds very well.

Mids
"Luck Be a Lady" (Sinatra live at Carnage Hall), his voice is immaculate and it seems like you are in the same theater listening him sing. The rest of the instruments sound well separated from each other and with a high level of detail.

With classical and melodic music, the voices and instruments sound organic and with a hint of forwardness. This also shows a well controlled bass execution that does not muddy the mids.

The midrange frequencies in general have a character approaching neutral, accentuating a bit in the upper midrange registers. Vocals in general are presented with great naturalness and have good clarity and presence in their reproduction thanks to the slight elevation between 1.5 to 2.5 kHz.

Treble
Sibilance is very noticeable in "Come rain or come shine" (Sinatra live at Carnage Hall) when the trumpets and cymbals sound together. This also happens in "Teach me tonight."

"Black Magic" (Slayer live) the cymbals at the beginning of the song are piercing at medium and high volumes. The lead singer has good focus sounding clear and prominent.

"No retreat" (Destructo) the bass is again well-presented, and the bells at 1:52 are quite sharp and overly bright, even at what are considered low volumes.

"S" sounds in "Strangers by nature" (Adele) have an exaggerated character.

Soundstage & imaging
Being a semi-open design, these headphones allow for better sense of spaciousness than IEMs or closed-back headphones. Its soundstage is not huge but it does expand a bit around the head. More wide than tall, but with good depth.

For the price, the imaging and separation that the 668b offers are incredible. Instruments can be differentiated from each other with clarity, their location and the distance between them on the stage can be perceived. There is also excellent articulation between voices and instruments.

I always test these two items with "Rime of the Ancient Mariner" (Live at Long Beach Arena). It's spectacular at minute 1:20 how you can tell with these headphones that the bassist and one of the two guitars are on the right side of the stage and the other guitar is a little to the left with the singer at the center. I can't always capture this detail, and the Superlux surprised me for the better.

Also in "Hydrogen" (M.O.O.N.), a song where the left to right movement of the bass notes is excellent, it covers the three important positions as it should (left-center-right).

Personal note
Its resolving character can become fatiguing at higher volumes and for genres that have many string instruments (rock or classical music with violins).

Conclusion
At the beginning of this review, it might sound like these headphones have more cons than pros. Ultimately, as someone who reviews audio products, I have to be as objective as possible, and yes, their comfort will leave something to be desired for some individuals (I don't mention it in the review, but it's not my case). Setting that aspect aside, the price to performance offered by the 668b is one of the best that can be found for over-ear headphones under $50: spectacular resolution, punchy yet well-controlled bass, organic-sounding vocals and instruments. If you're not afraid of treble or listen at low to moderate volumes, I am 100% recommending these Superlux headphones for budget-conscious audio enthusiasts.

Introduction
Many times we find ourselves in situations where we need a pair of small, portable, and wireless earbuds to simply put in our ears to listen to music/videos, block out the noise around us, and go for a walk, commute, do exercise, among other daily activities.
That is precisely why I dedicated myself to reviewing the Samsung Galaxy Buds2, a pair of earbuds that can currently be found for $70 and offer excellent portability with noise cancellation (ANC) and a fun and relaxed sound that goes very well with current music genres.

Disclaimers:

• ANC was always on - I found it most appropriate to test them with ANC on since their general use will be more oriented towards people who commute daily and need portability and noise cancellation to enjoy their music
• I bought the product myself.
• Review based on my own opinions formed within a 5-day period of relaxed and analytical listening (2 to 4 hour sessions per day).
• Devices used: Samsung Galaxy A50, PC with Windows 10 Pro.

If you wish to read this review in spanish, you can click here

Unboxing, build and accessories
The Galaxy Buds2 come in a compact but well-designed box that fits everything while wasting the least amount of cardboard possible. Inside, you'll find the charging case with the earbuds inside, the cable for charging the case (USB-C to USB-A), spare eartips in small, medium, and large sizes, and the user manual.

Regarding their build, both the charging case and the earbuds themselves are made of plastic with a glossy/satin finish. Despite the material they are made of, they do not feel cheap, and the lightweight construction of this material is appreciated.

Each earbud has two microphones that are responsible for filtering external noise (the black dots) and also an microphone for calls and a position sensor. Speaking of the case, on the outside it has a USB-C port and on the inside it has some little holes where the earbuds rest and charge. The magnet that keeps the case closed feels secure as well as the magnets that keep the earbuds in place.

Now onto comfort, the shape of the earbuds fits well with the ergonomics of my ear, but they stick out quite a bit and are not recommended if you want to sleep with them. They fit securely, but when I stretch or tilt my neck to one side, they seem to fall off, meaning they won't fall off unless you try to make them.

Tech and battery performance
As I know that a lot of websites on the Internet provide information about all the technologies that these earbuds have, I'm going to go straight to their functionality based on my experience with them.
To start, both earbuds have touch controls with multiple uses. Here are the functions that each gesture performs:

• Press: Play or pause a song
• Double press: Play next song
• Triple press: Play previous song
• Press and hold (customisable): Bixby/Activate or deactivate ANC/Increase and decrease volume.

During calls:

• Double press: Answer or end call
• Press and hold: Reject call

These touch controls are quite finicky and may activate accidentally when adjusting the earbuds in your ear. However, the controls can be disabled through the Galaxy Wearable app, which provides a great user experience.

Regarding codecs, the Galaxy Buds2 supports AAC, SBC, and Samsung Scalable Codec (SSC). SSC adjusts the bit rate from 88 to 512 kbps to maintain the best possible audio quality and connection, but it is only available for Samsung phones, limiting the capabilities of these earbuds for people who own phones from other brands.

About ANC, it is quite good: it cancelled a lot of traffic noise during a 1-hour SUV ride. The sound of tires against the pavement was still present, but it never bothered me when playing music. Walking on the street with them can be dangerous with ANC on, as they greatly attenuate the noise of motors in general, but like most headphones with this technology, they fail to properly attenuate mid and high frequencies. Also, with ANC on, a hissing sound can be heard when there is no music playing or in music with passages where the volume drops a lot, it is not annoying but somewhat audible.
The noise cancellation modes are: active noise cancellation (ANC on), ambient sound, and off. The ambient sound function is useful when engaging in conversations as it allows voices to pass through transparently, avoiding the need to take off the headphones to chat.

Then, regarding the battery, for sessions of more than 2 hours (approximately 2:30 hours) with ANC on and the earbuds at 40% volume, the battery went down from 100% to 65% (approx), so I would dare to say that if you don't listen to your music at maximum volume, it is most likely that they can last even a little more than the 5 hours of playback that the brand guarantees on its website.

Other important details to consider:

• The Buds2 are not compatible with eartips from other manufacturers, they can only use the ones provided with the product (and I imagine Samsung must also sell replacements).
• They have good compatibility with Windows and the latency is decent (not suitable for competitive gaming but good for watching videos or listening to music).

Frequency response description

• Bass boosted (particularly the midbass) that bleeds into the mids​
• Mids are recessed but not veiled​
• There is an 8kHz peak but from experience the earbuds never got sibilant at all​
• Treble does not retain a lot of detail (lacks air)​

Subjective sound description

I listened to my usual repertoire of classical music: The Four Seasons (Antonio Vivaldi performed by Fabio Biondi), Swan Lake (Tchaikovsky performed by The Boston Symphony), and Creatures of Prometheus (Beethoven performed by Freiburger Barockorchester) and I really can't recommend the Buds2 for this genre or similar ones. As I have read and now confirmed, Bluetooth transmission causes details to be lost in the high frequencies. This, along with the emphasis on the bass notes in the tuning, makes the violins, cymbals, and bells sound muted in comparison.

I had better luck listening to popular new music. I really enjoyed Caravan Palace and Swedish House Mafia. Speaking about the former, "Aftermath" sounds rich and full (one could say warm), the bass execution is very good, with correct speed and a lot of presence (thanks to the driver's woofer). Another song that retains good qualities with these earbuds is "Wonderland" by the same band, the driver has no problem reproducing all the different sounds (trumpets, autotune vocals, and synthetic sounds) with great transparency. It's very unusual, but despite not performing the best when string instruments are present, these earbuds retain a good level of separation in electronic music. Lastly, "Midnight" is a song that these earbuds make super fun, the bass gets into your head with a lot of impact while that saxophone and background voice create the perfect atmosphere to listen to during some action scene, I love it.

Moving to Heavy Metal, in "2 minutes to midnight" by Iron Maiden (studio album) the bass bleeds into the mids, causing the singer's voice to not sound as clear as it should. Like in other songs with multiple string instruments, separation is not their strong point. However, the electric guitars retain some definition (enough to be acceptable). The same applies to cymbals, they are present and can be heard, but do not have much authority at all.
In the case of "Revelations" by Iron Maiden (Live at Long Beach Arena), the guitars tend to get congested when playing together. There is a good presence of the lead singer despite the elevated bass.

A great song to demonstrate the balance between bass and midrange is "Miss You" by Adele. Drums are playing in the background while Adele and one/two backup singers sing. In this case, Adele's voice is a bit overshadowed by those drums. The cymbals have a correct impact. Her voice sounds organic, but recessed (as shown by the graph).

Lastly, "Vivere" by Bocelli: I know it is a song a use a lot on my reviews but it has a reason behind it. Vivere has it all: male and female vocals, cymbals, strings. In consequence, I am able to analyse each instrument or voice every time I replay it.
As it has been said, midrange is recessed in the mix, that’s why vocals don’t seem so intimate here. The driver retains the cymbal splashes and some drum kicks but fails to separate the instruments from each other, sounding congested at the end of the song, where all the instruments and voices sound in unison.

Conclusion

The Buds2 is a product that leaves me satisfied for situations where portability is strictly necessary, such as commuting or exercising. They have several strong points, such as an ANC that blocks low frequencies well and provides a high level of isolation, their very good battery life, and their relaxed tuning, ideal for travelling and enjoying the scenery without focusing too much on the details. However, as I mentioned, outside of portable situations, I don't see much sense in using them, such as at home, since many wired products have a better price to performance ratio and allow for more faithful reproduction of lossless audio content.

Introduction
Do you guys also experience annoying noises in your audio when using the audio input on your phone (for those who still have phones with a headphone jack) or on your PC? Well, that's exactly what was happening to me two years ago, particularly with in-ear headphones that tend to have low impedance and high sensitivity, which makes them extremely sensitive to any signal transmitted by the device they are connected to.
This little guy saved my ears: this is a review about the TempoTec Sonata HD Pro (yes, I am a little bit late to the party haha), a dongle dac/amp that goes for $39 (but can be found in AliExpress for $30)



Unboxing, build and accessories
This dac/amp dongle comes in a cute metal box, which contains the device itself, a micro USB to USB-C adapter cable, a USB-C to USB-A adapter, and a sticker. The dongle has an awesome built for $35 USD, it has a good black metal construction with two buttons that allow for volume control, and it doesn't look cheap at all. Furthermore, from my personal experience, I can attest that it is very durable. I have taken it on trips several times and it has even fallen to the ground during a rainy day, yet it still works just like the day I bought it.




Specifications
The TempoTec Sonata HD Pro is a dongle that performs a double function: it serves as a DAC (Digital to Analog Converter) and also as an amplifier, providing a power of 2Vrms (110mW at 32Ohm on high gain mode), making it an ideal companion to use with a wide variety of headphones, from in-ears to over-ears that do not have very low sensitivity (+95 dB (1kHz/1Vrms)). It also has DSD 256 decoding and offers a resolution of up to 32bits/384 kHz.

Performance (music and gaming)
This little guy can give you more volume than you can ask for in almost any portable situation that I can imagine. On my phone, I can only listen at 25% of the volume level provided by the phone at maximum. How is this possible? Let me explain.

As mentioned, the dongle has buttons to control the "steps" that can be taken in volume. However, what I did not mention is that those buttons only control the volume that belongs to the dongle, leaving apart the volume of the device it is connected to. Ideally, the dongle volume should be at max and the volume of the device connected to should be the one to be regulated. On my phone, I can only turn up the volume four steps at most before it gets too loud for me (which represents 25% of the 15 volume steps of this device), while in Windows, I can only raise the overall volume up to 10-12, which is insane!

As for the headphones I used with the dongle, they include Sennheiser HD 558, Hifiman HE400SE, KZ DQ6, Moondrop Aria, and HZ Sound Heart Mirror. Of these, only the HE400SE seemed to need more powerful amplification (even with the high gain trick applied) given their magnetic-planar driver technology, but for the levels at which I listen to music, they worked properly.

The best aspect of this little guy is the practically non-existent floor noise it has. This was a blessing for me because when I started taking this hobby more seriously, I couldn't use any type of headphones with my phone due to the high and annoying floor noise it had. That noise was reduced to something inaudible thanks to the Sonata, and the best thing is that it is also compatible with Windows, so I could use it on multiple devices.

One pleasant surprise with this dongle was how well it worked on Windows. For that reason, I started using it for gaming and really felt a difference in competitive games, shooter games in particular. With such a low noise floor, enemy footsteps or combat situations in Battle Royale type games became much more noticeable (some may consider this a competitive advantage).

In technical terms, the sound profile tends towards analytical, without colouring the sound at all. It presents a wide soundstage (but not as wide as a desktop dac/amp) and good amount of detail in the treble region for such a small device. As a dongle with a colder profile, the voices and instruments don’t have that warmth that many people prefer but is suited for those who like to analyse the music and all of its sounds in detail.

One issue I encountered was that without updating the firmware to the latest version (which can be found on this page: http://www.tempotec.com.cn/chs/4-Company/driver.htm , thanks to user ALC220 who made this link available in the comments on Audio Science Review), the dongle suffered from many cutouts when connected to my phone. After updating the firmware, the presence of cutouts/popping noises decreased significantly but is still audible when fast forwarding or rewinding a video or music track.

Finally, if any other defect has to be mentioned, it could be that the device has an "old" input (micro USB) and that it can heat up when in use due to using the phone battery or PC power to work, but as far as I'm concerned, it doesn't get to the point of bothering me at all.

High gain trick
This "trick" is already well known in the audio enthusiast community and consists of the following: this dongle has two modes, one that recognises low impedance headphones and another that recognises high impedance headphones. The latter offers more power when amplifying headphones, so wouldn't it be convenient to be able to always use it? In order to achieve that, we just have to connect a 3.5mm cable without the headphones connected to the other end, which will make the dongle go into "high gain" mode, then connect our headphones to that same cable and voila!

Conclusion
In summary, this little device gets my recommendation. It allows for a high level of portability with tons of power and a noise-free DAC that simplifies the life of those with audio ports problems like mine.

Introduction
Have you ever wondered: "I want to experience a different tuning than Harman within a budget". Wonder no more with this review of the HZSound Heart Mirror, an IEM tuned to follow the IEF Neutral tuning coming at $35 (and now replaced by his sibling: the HZSound Heart Mirror Zero, also for $35)



Disclaimers

• This review is based on 2-4hs listening sessions across 7 days - IEM used with stock tunning and accesories
• Favourite music genres: Heavy Metal, Classical, EDM
• Only lossless music from Qobuz
• Gear used: Fiio E10K, TempoTec Sonata HD Pro (BHD firmware)

If you would like to read this review in spanish you can click here

Unboxing, build and comfort

The HZSound Heart Mirror come in a medium-sized box with a sliding system that reveals the IEMs and their case. Underneath the case, we find a large number of ear tips to use: 3 pairs of white silicone ear tips (balanced) in sizes S/M/L, 3 pairs of black ear tips (bass focused) in sizes S/M/L, and a pair of foam tips. Also, the Heart Mirror comes with a clip to attach to your shirt to avoid cable microphonics. Speaking of the cable, it is a 4-core 2-pin 0.78mm silver-plated oxygen-free cable (OFC). It is a fairly complete package for the price, and personally, the black tips and the cable are two of the accessories I use the most when testing other IEMs.



Focusing on the IEMs themselves, they have a 10mm dynamic driver with a nano-carbon diaphragm. These are protected by an electroplated zinc housing with a glossy finish, which makes them feel very premium for their price, but also makes them a fingerprint magnet and easy to scratch with any sharp surface.



In terms of comfort, the size of the IEMs is relatively small (there is a comparison with the KZ DQ6 below), so they fit very comfortably in the ear. However, I could only achieve a partial seal in my right ear with any type of the eartips provided, so I would say that the comfort is only decent at best.



Frequency response description

• IEF Neutral tuning
• Sub-bass and bass that do not bleed into the mids but extends well
• Accentuated highs (fatiguing), that provide a lot of detail and clarity
• Tuned for analytical listening

Subjective sound description:

Starting with Iron Maiden, “Powerslave” (Live Long Beach Arena), the imaging is precise with good separation between the guitarists on either side. The lows from the bass guitar sound behind in the mix and may even be difficult to find in situations where the instruments play in unison. From the same live performance, in “Running Free”, the bass is present at the beginning of the song when it is presented alone and has good definition.

Continuing with classical music in The Four Seasons, Concerto in F Minor, RV 297, Op. 8, No. 4, "Winter": III. Allegro, the clarity of the string instruments (violin, double bass and harp) is excellent although they can sound a bit metallic (this happens with most instruments that live in the treble region). Microdynamics can be appreciated during moments such as a person stroking the harp strings to play while the violin plays as the protagonist. Overall, with all of Vivaldi's Four Seasons repertoire and classical music, these IEMs demonstrate their true strength. However, being so resolving, they do not offer that relaxed listening experience that many people seek.

It was very enjoyable to listen to Adele's album "25" with these IEMs. During "I Miss You," the soundstage is wide and the separation of the instruments in space can be appreciated. Also, distant instruments like a maraca or tambourine can be appreciated on the left side of the mix. On the other hand, in "When We Were Young," the different voices harmonize articulately, and the three participating voices can be distinguished clearly along with the drums and piano in the final stretch of the song.

Continuing with another great artist, Amy Winehouse's 2006 album "Back to Black" is an "old" album in which some songs seem compressed and even congested. However, Amy's voice is always present and in a very intimate and enjoyable way.

Moving on to male singers, a song that I always like to listen to is "Vivere" by Andrea Bocelli, and I have to say that this IEM does not disappoint here. Both the female and male voices have a well-marked authority in the song with the piano and bass following a bit behind. The presence of both types of voices is a virtue as well as a course due to how fatiguing they can be for long listening sessions.

For me, another great male singer is Sinatra. While singing "Luck Be A Lady" (Live At Carnegie Hall), I have to admit that the trumpets sound sibilant. Sinatra's presence is exceptional here. You can really hear the width of the soundstage of these headphones. The reverberations that Sinatra generates through the speakers in the theater can be heard and that is incredible for an IEM under $50.

Last but not least, I tested the sub-bass in "Grnfthr" by Spark Master Tape. This song has powerful sub-bass, and the Heart Mirror represents it without problems. They have a very good extension that goes down to 30-40Hz. However, with how they are tuned, you cannot expect that meaty bass that makes you shake your head to the beat of an EDM song drop. I would not recommend them if the genres you consume most often are Hip-Hop, EDM, or others where the bass has great predominance.

Conclusion

The HZSound Heart Mirror are headphones that I can recommend to those who seek to listen all the little nuances in music and prefer genres such as classical, opera, or melodic music. I cannot recommend them for everyday use since they are extremely fatiguing headphones that make you concentrate on the music at all times. However, I believe that these IEMs are a must-have for every person to complement their collection by offering a sound that deviates from the Harman Target and provides amazing sound quality below $50.

About me
Hello, I am a 23 years old Argentinean audio enthusiast. I have been enjoying this hobby for quite some time (~5 years) and recently I started writing reviews about the products I own in order to bring insight of them. I speak spanish as my mother tongue so if you wish to read this review in spanish you can head to my wordpress blog.
Disclaimers:

• This product was purchased with my own money
• The review is based on 2-4hs listening sessions across 7 days - IEM used with stock tunning and accesories
• Favourite music genres: Heavy Metal, Classical, EDM
• Only lossless music from Qobuz
• Gear used: Fiio E10K

Introduction
This review will be about the Knowledge Zenith (KZ) DQ6, a triple dynamic driver IEM priced at $20.99 usd (found in Argentina for $41 usd)

Unboxing, build and accessories
The IEMs come in a small and simple box, in my opinion nothing to worrying giving the price point. At first sight, the IEMs are inserted into a hard foam to protect them from scratching. Under that foam, the cable and three pairs of extra eartips can be found.

The KZ DQ6 have a 3 dynamic driver configuration which are contained within an acrylic shell. The faceplate of the iem seems to be some kind of metal/aluminium and comes in to different colours: matte gray or silver. The cable that comes in the box is okay but the eartips can difficult the fit of the DQ6. If you have some preferred aftermarket tips, I recommend you use those instead.
Regarding comfort, the shape of them is perfect for my ears and I can use them for long listening sessions with some adjustements here and there.


Frequency Response Description

• Mild U shape (bass and treble boost)​
• Good extension under 100Hz​
• Recessed mids (1k region dip)​
• Good "air"/detail in the treble region (can be quite fatiguing for some)​

Subjective Sound Description
I divided this segment in two categories: gaming performance and musical performance.

Gaming
In this category I tried two kinds of different games: a Singleplayer game to test the level of immersion I get from this IEM and a Multiplayer game to test the imaging accuracy.

.Dying Light (Singleplayer)

• With a good fit they provide excellent isolation and make a pretty immersive experience
• Not a lot of spaciousness but you can infer the distance between each zombie on the streets
• The voice acting of NPCs sound natural with a good sense of right to left feeling
• Explosions during the campaign can sound a little bit harsh

.Apex Legends (Multiplayer)

• Footsteps coming from right/left are rather easy to hear so as is to discern when an enemy is running or jumping
• Gunshots can sound too strident for my liking
• Sense of spaciousness and imaging got better overtime. The first 10 matches it seemed kind of difficult to locate enemies inside buildings. When you get familiar with how this IEM sound it becomes much clearer.

Music
Starting of with Iron Maiden (Live at Long Beach Arena) the instruments sound and voices sound natural and organic. However, the presence of the bass guitar can feel a little too much due to the tunning of the DQ6. Imaging does good in songs like "2 Minutes To Midnight", to guitars up front with the singer and the drums further back.

"Vivere" by Bocelli sounds right, the voices sound natural but female vocals seem a bit more emphasized than male vocals. On the other hand, during "Spring" from The Four Seasons (directed by Fabio Biondi) I find a decent sense of clarity with the triple driver configuration offering good resolution.

EDM is a genre where this in ears shine. The bass sounds punchy and extends well into the sub-bass region. Can get a little congested in more complex tracks.

As mentioned, female vocals have more presence in the mid region. I find it quite pleasant to listen to songs from Adele and Amy Winehouse.

Lastly, Yosi Horikawa's work shows that the soundstage on the DQ6 is average at best. It also reveals good left to right imaging but the stage is neither deep nor wide.


Conclusion
KZ DQ6 offers a good value for the money. Is an IEM with good build quality and can shine in genres like EDM, Rap, Pop and Hip Hop. They are quite versatile as well, but the genres listed are the ones that favours the most. If you can get around some of the caveats like not a very attractive unboxing experience and the low quality eartips, I believe it is a great IEM to get into the audio rabbit hole.