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Hidizs Mermaid MM2 Review

by Chris Love

  Hidizs Mermaid MM2

The Hidizs Mermaid MM2 ($80-89) is Hidizs Audio’s latest in ear monitor. Lately Hidizs has created some very nice iems, particularly in the budget sector. In my possession is also the Hidizs MS2 which I do regard as one of my top 10 iems under $100. Hidizs has always sought out to manufacture well-built audio gear with a distinct look as well as sound.      

Can the MM2 best it’s older sibling to take the helm at under $100 range within the family or is it simply another iem in a clogged market? It seems Hidizs went back to the drawing board to come up with a new design to tempt the consumer. I am a sucker for an innovative new design and I’ve come to really appreciate Hidizs. Granted there is nothing new here in the grand oceans sized market of iems. However, these tuning filters design and effectiveness is rather unique. Let’s see how Hidizs did with the MM2 and compare it to some heavy budget hitters.


-Not difficult to drive

-Bass is deep and punchy

-Good soundstage

-Decent separation

-Tuning Filters that work

-Fun tuning


-Odd treble at times (balanced/treble filters)

-Treble rolls off too early

-Odd look on the ear (to me)

-Using the bass filter = just too much

Gear used

-Shanling Ua2

IFi Go Blu


Left to Right: IFi Go Blu / Ibasso Dx240 / Shanling UA2


   For a set priced at $80, Hidizs put together a nice package. You receive 6 pairs of tips; #3 wide bore and #3 with a more narrow bore. All of the tips are actually usable as they are more firm, as both styles included aren’t just cheap, flimsy throwaways.

   Also included is a 2 pin- 4 core OFC copper cable, much like the cable handed out with the Hidizs MS2. The cable is light and easy to manage with a soft and pliable feel to it. It terminates with a 3.5 TRS single ended jack. It really is a nice cable considering the price and what we’ve come to expect from budget tier iems.

   One thing which surprised me was the case. It is a very nice and even premium looking faux leather case. Really, I did not expect a case which felt so nice in hand. I have so many cases and rarely actually use them but this case prompts me to use it for…something. Who knows I may actually put some iems in this one. Eh, or not.

   Last but not least is the small rectangle aluminum slab which is home to the screw on ventilation filters. I recommend utilizing this little slab so to never lose the filters. This is similar to multiple other little filter holders, as you can see pictured below. Within that slab you will find the “Bass”, “Reference”, and “Treble” with female threaded holes to each corresponding filter.



   The Hidizs MM2 employs a dual cavity/dual voice coil 10.2 mm Dynamic Driver which Hidizs calls a “PEK  Macromolecule Polymer” Diaphragm. From what I have read, the Dynamic Driver covers the lows and mids. To control the treble area is a 6 mm Magneto-static Driver. A unique hybrid driver setup which doesn’t disappoint.


The look of the MM2 is unique and also… kind of odd in my opinion. They aren’t ugly at all but maybe not my jam. This is obviously an entirely subjective observation. They just aren’t something I would “Rock” daily. I’m sure some may really like the look of these but the tuning filters which stick out and look… somewhat Blingy to me. Perhaps it is the silver color which adds to the boujie look. For me the MM2 are comfortable and seal very well. Obviously, this may not be the case for everyone.

   Built well enough with a sturdy frame, the MM2 don’t feel too cheap to the touch. They have a transparent resin housing with what appears to be an aluminum faceplate. The MM2’s in my possession are a silver color while Hidizs also offers a Black MM2 as well. They are very lightweight, easy for wearing and without any jagged points of contact to annoy over time. Hidizs always has great build quality and the MM2 carries on this trend.

   Atop the Faceplate you will find a screw type tuning filter with a rather long screw which sticks out quite a bit. Of course, Hidizs had to build them in this way so that a person like myself can get a grip on the filter head to screw in and out. Nowhere near as easy and quick as something like the Bqeyz Autumn but still easy enough to install nonetheless. Righty-tighty, lefty-loosey.

As far as the build is concerned, I’m sure this look will appeal to many. It took a while for me to come to grips with the blingy appearance but after some time I guess… it’s not so bad. In fact they may actually grow on me.

Hidizs Mermaid MM2

Sound Summary

   I should start by saying that I didn’t hear any sonic benefit from burning in the MM2. I stopped at 50 hours without change. Good out of the box.

   I would categorize the MM2 as V-shaped to U-shaped. However, the midrange isn’t crazy recessed like the majority of V-shaped iems flooding the market nowadays. The mids sound in good balance with the rest of the staging. The sound is like a mix of natural and colored. Warm in the lower region while cooler in the mid tones. I don’t hate it at all, especially with certain genres. There is nice clarity throughout with these drivers which is becoming a staple of the Mermaid line.

   The MM2 has a fun signature as there is nothing dull about this set. The bass hits great with any filter and much more so with the bass filter. The lower midrange is full and rich on all filters while the upper midrange has more emphasis. The treble drops off fast after the mid treble area but doesn’t sound terrible to me. Just missing a bit of that energy and sparkle up top.

Each tuning filter will alter the sound to the relative naming scheme of the filters. Most tuning filters seem more like gimmicks which only subtly alter the tonality. I have seen this time after time. In fact one of the comparisons later in the review, the Fiio FD3 also has tuning filters which hardly have the effect that the MM2 filters have. The MM2 is constructed in such a way, that each filter does exactly what their name implies. To a degree. Obviously nobody should purchse this set thinking they are getting three iems in one. The change is really just shifts in the tonality, but they do actually have a nice affect.

The bass digs deeper with excellent speed, a tight response, and is punchier. The mids are smooth, detailed, and have a more U-shaped character. Vocals are sweet and instruments sound natural.

Large soundstage, outstanding imaging capabilities, excellent layering throughout, with great presence – MM2, a pair of IEMs you’ll never regret having”.

Hidiz Promotional


   I used the included cable for most of my listening. However, I found that using a balanced cable seemed to help with this set. It aided the playback by providing more power using balanced sources as the MM2 does scale to an extent in my opinion. To be honest once I switched to the Tripowin C8 SPC balanced cable, I didn’t go back.

   Overall, these are easy to drive. I had no problem driving them from the lower powered Zooaux Dongle Dac. I would say that the bass wasn’t as quick using this. A bit slower in my opinion. Not bad though. The MM2 have an 18-ohm impedance and a sensitivity of roughly 104 db per their website. Just as the Hidizs website states… these are pretty easy to drive.

    However, from a Dongle Dac such as the Shanling Ua2, the MM2 seemed to find itself a bit better in the bass department. Then, moving up to the Ibasso Dx240 DAP with a balanced cable I found the MM2 does benefit a bit with more power. The bass became quicker and tighter and played better with the upper areas of the mix. I noticed a bit more openness and dynamics. Please note, the MM2 are very dynamic without the added power as well.

   The MM2 don’t need big power. A desktop setup is not a requirement for better fidelity. Simply add a Dongle Dac or a Dap and you’ll be good to go.

(In the next section I chose the Reference Filter as I think it gives the best balance of all three filters.)


   To me, the low end is one of the main characters to the MM2 story. I’ll tell you what…I dig the pronounced low end here! I found clean edges to some pretty heavy bass drops without them impeding on the rest of the mix. “Big Energy” by Latto is very representative of this. In that very toe tapping song (be aware it’s dirty) there is enough commotion going on in each area of the frequency. I feel the MM2 handles everything well, with clarity and with a decent slam while not suffocating the mix. I hear great energy. Keep in mind the bass is on the slower side but still does well to not muddy things up. I do hear some texture here and clean edges.

   There is more volume to the mid-bass than the sub-bass but from what I hear the difference is minimal. That said, the sub-bass is still a big part of the MM2’s appeal. There is evident haptic buzz vibrating my ears. People who enjoy Hip-Hop or EDM will likely enjoy the MM2 a lot. Rock and Metal sound fantastic on the MM2 as well. In fact rock music seems particularly at home with the MM2.

   The low end of the MM2 is not too overbearing even with the thump which comes from this set. This pair falls short of bass head with the reference filters. I feel Hidizs added just enough weight to the low end to not infringe on the rest of the mix. The upper bass does bleed ever so slightly into the lower mids. Though that bleed over is barely noticeable and actually adds some meat to the lower mids.

   With the bass filter attached the bleed further interrupts in my opinion. We get a bit of bloom and boom with this set-up. I don’t like it as much. I’m sure some reading this will enjoy the bass filter just fine. I’ll stick with the reference filter.

  The bass hits hard with a vibrant kick from drums as well as synth bass, booming bass drops and bass guitars etc. There is some coloration to the low end, yet done in a way so to not sound too unnatural while still giving that thump. The bass is quicker than it is slow with added power (using Dx240) and slightly warm of neutral. I can attest that a bit more power does help here.

   The lower parts of the frequency are a joy for me. However, some may find the bass to be too much on the MM2. Not everyone enjoys an expressive bass as I do and so this may be a problem for some.


   The lower midrange is a tinge more forward than most. Nothing sounds out of place or too distant as I don’t think there is any drastic recession. Granted, the low-mids to mid-mids is where you will find the greatest recession on the MM2. Male vocals cut through nice with clean edges. Nothing grainy from what I hear.

    Male vocals come across as full and articulate. Though at times I do hear a very slight bit of congestion. Mostly when there is a more congested track while using a lower powered source. It’s nothing terrible but the MM2 can sound a wee bit too mushed together in a perfect storm. This is a rare issue though. Still, the male vocals have good weight and sound a tiny bit colored. This coloration in my opinion only adds to the whole presentation.

   When male vocals are more singled out, they sound great. There is a grain free edge to voices in this area. There is almost a plump intensity without coming across too intense, if that makes sense. I don’t hear any great warmth mudding up this area from the bigger bass either.

   Acting as a counterbalance to the low end is the steeper rise in Pinna Gain, quickly rising into the upper mids. I find it necessary for a good balance across the spectrum. I don’t hear any shout or pierce at all, unless I really crank the volume on a track which is more prone to shoutiness. At least that is how I hear it. Somehow Hidizs struck a good enough balance as a whole.

    Female vocals sound nice enough. Nothing veiled to me. Maybe a hair thin in comparison to male vocals. Nothing sounding odd though. Slightly more forward is the female vocals over their male counterparts. I hear a sweetness to females at best. What I don’t hear is that emotional pull which some female vocals can Induce. They are clear and pleasing but settle at that. I would not call them dull.

Instruments also sound well resolving and for the most part the timbre sounds fine. Tonality is somewhere near neutral to cooler than neutral in this area using something like the Ibasso Dx240.

   All in all, the midrange is fine, with some decent to good details in its replay. On louder volumes and in some tracks, you can hear the beginnings of shout, but nothing too bad. I’m sure many will enjoy the vocals on this budget tier iem.


   The Magneto-Static Driver completely controls the treble region. The treble as a whole sound just fine, if not a little subdued.

The lower treble region does have a bite, a spiciness that adds some life to the upper frequencies. The treble as a whole is not as voluminous as the bass and midrange but nothing sounds as though anything is particularly lacking.

   The treble does have a small issue for me. Not in every song do I hear this issue. The issue is the steep drop off somewhere before the upper parts of the treble, which leaves some information lost and luster-less against the rest of the frequencies. For instance, Cymbals are a slight bit clouded over in more active and congested songs. Also, around the upper-mids and through the treble is a very slight grain to the edge of notes. Not a deal breaker. Technically speaking, the treble area still picks up decent details which I suspect is the result of good resolution and clarity.

     Understand that I am nit-picking. This is a $80 iem. The treble is just… fine. I just don’t hear the extension all the time. Like I said before, this isn’t a problem on every track, and it can go unnoticed completely. Unless of course you are a diehard treble head. In which case you would never reach for this set in the first place. This MM2 is not perfect, not that I should expect perfect, but other sets in this price point are able to do better here (treble). Hey, the MM2 are doing pretty darn good so far despite any shortcomings.

Hidizs Mermaid MM2 and the Shanling UA2. “Kbear 07” tips & the “Tripowin C8” SPC Cable


   Represented very well is the soundstage, I’d even call it one of the MM2’s steengths. There is apparent audible openness in the sound scape. Really, I think that Hidizs did a good job of giving the illusion of space. I hear above average width from the MM2. Keep in mind that above average is a great asset in this price point. Not every set can provide an above average soundstage. The width is appropriate to the music, and you aren’t lacking anything here.

  The depth and height is a hair above average. Though I think more height than depth. The stage gives ample room for instruments and voices to mesh yet remain separated at the same time.


    Another strong point. The imaging of the psycho-acoustic stage is actually… done well. I didn’t expect this. I hear decent to good instrument placement that is accurate. At this price anything that can induce the perception of instruments in their own place is a win for the MM2. Separation is above average for sure. There is enough space to put each element within a song in its own space with air between.

   The MM2 has enough air in the mix as well as resolution to compete well against iems in its price segment. I’m not talking multi hundred-dollar level here. I’m referring to the Iems stationed at that $50-$100 range. These won’t blow your mind, but they also won’t muddy things up so much that they are hard to listen to. I’ve said it a few times; there is very good resolution and clarity here, as seen in previous iterations of the Mermaid series. This only aids the audible placement of instruments and voices. Not bad Hidizs.


Left to right: Fiio FD3 / Hidizs Mermaid MS2 / Hidizs Mermaid MM2 / Whizzer Kylin HE01 / Moondrop Aria

Moondrop Aria  ($75-80)

   The Moondrop Aria is an iem which reached legend status farely quickly. The Aria has a Single Dynamic DLC Diaphragm Driver and has a Harman type tuning. This iem is in many Top #5 lists for its easy to listen to replay.

The first thing you’ll notice is the Aria has a much more smoothed over presentation. More laid back than the MM2. I would say much easier for extended listening.

  The stage of the Aria is slightly smaller, but they are on par with each other in placement of instruments and overall staging. The Aria has been highly regarded for its imaging, so to put the two in the same sentence says alot.

   I believe the MM2 has a hair better clarity and resolution but also harder edges. The Aria is much more balanced in its replay and a bit more cohesive altogether.

   The MM2 have more bass quantity as well as quality to me. That said, the MM2 is also more elevated in the upper-mids/lower-treble area creating a more V-shaped sound. Still vocals sound good on both sets but more natural on the Aria to me.  Vocals seem a bit more effortless on the Aria.

   Aria has better extension in the upper regions, and you simply can discern these areas better on the Aria. Couple that with the great resolution and smooth replay and you have a fantastically tuned iem. The Mermaid is no slouch though and I could easily see many taking it over the legendary Aria. I suppose it’s a matter of preference. The MM2 are the more of a fun set, yet this certainly doesn’t equate to better. Just different.

Hidizs Mermaid MS2  ($75-99)

   The older sibling of the MM2 and one of my favorite iems in the under $100 price is the Hidizs MS2. The MM2 takes a different approach to a similar tuning. I can hear the bloodline of the Mermaid series with just different takes on it.

  The Hidizs MS2 is also a Hybrid Driver but with different configurations. The MS2 sport a 10.2 mm Macromolecule Composite Diaphragm, said to be a 2nd Gen Driver. Taking care of the upper regions; a Knowles Balanced Armature Driver which gives a very open and airy sound.

  It is clear when listening to these side by side that the MM2 has much more elevated bass. The low end of the MS2 may not be as exaggerated but it is much quicker and tighter. The MS2 has good punch with great clarity down low. The MM2 have more boom and heavy doses of haptic vibration.

Soundstage is actually a hair wider to me with the MS2 as there is a better balance across the spectrum with more extension up top. Of course, Hidizs wasn’t going for a balanced approach with the MM2 but a fun and slight V-shaped to U-shaped sound.

   All things considered; this is just another choice in preference. The MS2 is a bit colder in tonality while the MM2 has slightly more warmth due to the elevated low end. The MM2 is a more mainstream toe tapping banger, while the MS2 is a bit more refined to me. The MS2 has less of a veil but both have a more open nature. Both have great clarity. Both have great resolution. Personally, there will be times that I prefer either one of these two iems. Both catering to whatever mood or ambience I am after.


Whizzer Kylin HE01  ($80)

   The next iem for comparison is the Whizzer Kylin HE01. Comprised of one Single Dynamic PU / Peek Composite Material Driver, the HE01 at one point was a sort of “hype train” iem which did not last very long. They came and they went.

Actually, the Whizzer HE01 is a very unsung and almost forgotten about iem. This is a mistake. A/Bing these two iems side by side immediately shows they are both nice sets in the price point. Also very evident is the very fun sound which these two have in common.

   The HE01 wins in the bass department. Flat out. While I enjoy the MM2 for its decent thump, I can’t help but enjoy the same thump in the HE01 yet with better decay and more authority. The HE01 is tighter with more slam yet with smoother edges. The MM2 is slower but still defined. Both are nice but I like the HE01 a bit better here.

   Both sets present forward mids compared to other V-shaped iems. I don’t dislike either in the vocal dept. Vocals come across a bit more natural on the MM2 as the HE01 has more of a knife edge to some notes in the midrange. Two different approaches.

The HE01 has a little brighter tilt with a bit more extension in the highest regions while the MM2 is a hint warmer in replay. Both sound great in the $50-100 area.

   I think with the addition of the tuning filters the MM2 obviously has more options to tune them to your preference which is a win for them. Yet if you value bass that is tight yet carries authority with a replay that tilts to the cooler side of things you may pursue the HE01. Both have a certain Blingy element with the MM2 appearing more masculine and the HE01 looking almost like jewelry.

Fiio FD3 ($99 / $130)

Since it’s release a year ago, the Fiio FD3 has been mostly unsung. In my opinion the FD3 is one of the better single DD’s in the price point. Stylish, small and very fun are the sentiments which come to mind. The FD3 is a Single Dynamic Driver with a  DLC Diaphragm. Fiio refers to it as a “Flagship Level” Driver.

   I hear a slightly wider stage with the FD3 than the MM2 but the MM2 has a bit more depth. Both have wider and deeper soundstage than average however.

   The overall tonality of the MM2 is a bit warmer than the Fd3. The FD3 has a bit more extension past the upper treble area and deeper sub-bass than the MM2. That said, the MM2 also has a bit more 3D of a sound.

    The bass on both sets hit pretty hard with the FD3 coming out a bit tighter while the MM2 has a bit more slam in the mid-bass. Not by much at all though as neither lack at all in low end volume. The FD3 can vibrate a bit deeper in the sub-bass region. Both replay bass wonderfully for the price tier.

    Male vocals are more up front on the MM2 with a hair more weight, while female vocals sound more forward in the FD3.

    There is a bit more thickness and tighter edges to notes on the MM2 which helps with a very vivid replay. The FD3 are just as charming with a touch smoother sound and great tonality. As I said the FD3 has a bit more extension with a wider soundscape due to the larger back vent on the shell which lends itself to slightly thinner areas within the mix.

     Don’t shy away from the FD3 though. Fiio did a wonderful job on this Single DD. I think for longer listening sessions the FD3 may be the one to check out. Both of these sets are very fun however with the MM2 coming out a titch more crisp with a bit better resolution, but I am splitting hairs people. In truth I personally enjoy the FD3 as the fit suits me better.

    Every set I picked to compare are some of the best in the under $100 price bracket and none of these are head and shoulders better than the other. This was simply to establish the pedigree that the MM2 can play with if the tuning suits a person.

The Hidizs Mermaid MM2 are built well enough. As you can see the tuning filters are easy to get fingers on.


Starting this review, I have to admit that I was not exactly a fan of this set. However as I went through the process of testing and comparing I have come to enjoy them. The MM2 are certainly not for everyone. They cater to those who are after a very fun, dynamic, and very punchy sound profile. I did not find them too fatiguing either. Still, there are certainly other iems which are easier to listen to for long periods. Like I said, not for everyone. Hidizs seems to have their arrows directed at a more youthful demographic here. Still, I have to say that the MM2 represent this style very well. Especially if you are into Rock, Hip-Hop, EDM, or even Jazz genres I’m sure you will at the very least come away respecting what Hidizs created here.

I’ve come to respect Hidizs and the products they produce. I feel that they always do a good job of making solidly built and premium feeling audio gear.

This review is simply a snapshot of my views on this new iem. All thoughts within are from my perspective and are my opinions. We all have different ideas about what “good” is or isn’t. So now that I am nearing the end, I can attest that the Hidizs MM2 are representative of what good…is. Again, the MM2 is not my ultimate preference, but I understand what Hidizs was shooting for. Let me put it this way; If this set started showing up in multiple top 10, or even top 5 lists… wouldn’t surprise me. If it turns out that this just isn’t for a person…wouldn’t surprise me either.

So, this concludes my review of the Hidizs MM2. For $75 you can definitely find worse V-shaped iems no matter how you feel about these. All in all, not bad at all Hidizs. Take good care everyone.


Marc H. 23 May 2022 - 18:10

Thank you for the very detailed review on MM2. It helped me clear most of doubts.

Can you name a popular iem that has a close sound with this?

Chris Love 23 May 2022 - 18:49

Off the top of my head… Good question. These have alot of energy throughout. I should’ve done a a/b with the Tfz No. 3 because they seem close yet the MM2 has better resolution. Urbanfun ybf-iss014 is another one which comes to mind. There is a slight resemblance to the Blon 03 in many ways except better resolution, details, quicker low end and the MM2 has a hair more energy in the upper mids.


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