Massdrop x HIFIMAN Bolt In-Ear Monitors

General Information

You can’t go wrong with a great pair of $10 IEMs—especially when they look, sound, and fit like earphones several times their price. Enter the Massdrop x HIFIMAN Bolt: one of those small daily essentials you’ll always be glad to have around. Featuring a well-built aluminum housing with silicone ear tips and one 9-millimeter dynamic driver per side, they provide good noise isolation and a fun overall sound. The sound signature includes warm lower mids, clear and present mids and upper mids, and highs that are slightly emphasized, though less so than the low end. For taking calls and changing tracks, the oxygen-free-copper cable is equipped with a one-touch condenser mic and remote. And for a comfy in-ear feel, these IEMs are extraordinarily lightweight: just over half an ounce.

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New Head-Fier
Pros: Good Build, Decent SQ
Cons: Some inconsistencies here and there..
Here it is, another collaboration from Massdrop. Coming from the K7XXs, Fostex TR-X series and most recently the Plus, there is definitely a look of surprise on my face when I saw that the new Bolt, an IEM that was born from the collab between MD and HiFiMAN, costs only $10. $10 guys! imagine, what can we get for that amount nowadays? Probably a one-time lunch or a short uber trip. But no, here with the Bolt you get what MD claims to be a budget IEM that is made by audiophiles, for audiophiles. a bit of Razer reference, eh? Anyways, will the claim stand or will it just be another marketing slogan by MD? Find out in this review!

Now I now I put up an intro already, so this section will address the types of music that I will test the Bolt with and my expectations. So, as far as expectations go, I expected it to be good but not at the level of the RE400s. I know that no company in the market will be willing to let a cheap product cannibalize their higher-lineup models, and so I had that mindset going into this review. Furthermore, although I will cut the Bolt some slack in this review, I still believe that no one should spend money on products that does not suit them, so I will be as transparent as I could. Even for $10, I know that some people might be willing to save that dosh in their wallet instead of having an IEM that they do not like lying around in the house, unused. Now for the music genre, I mainly test these with rock, edm, and modern pop.

Now MD really gets to me when it comes to their packaging. Some people might think its disappointing, but for me it is interesting as it shows their "in the works" state similar to what Off-White is doing with their products. However, with the Bolts I was disappointed on the inside... check it for yourselves:

Hmm.. Nice! Similar to the Plus' Box!

Will talk about these later...
Similar to Campfire Audio products.. but these come in cheap plastic
This. I HATE this. Makes these look like they actually are worth $10
You see the part I hate the most is the fact that they do not put any effort at all during the internal packaging. It feels like in the factory they just put them inside the clip and off they go. Even for $10, I expected more. C'mon MD I know you could impress me more..

---Build Quality & Fit---
The Bolt is made out of part aluminum, part plastic. The housing itself are encased in aluminum, which is a nice touch. The metal they use are similar to the ones present on the urBeats, with solid, smooth metal across the surface. Unlike the urBeats however, the metal part on the Bolt does not go all the way, as 1/4 ish of the housing is wrapped in what seems to be a solid feeling plastic. No problems there.
The stress reliefs are also pretty solid as well, which technically should give these better chances of survival in case of extreme tangling or unexpected pulls. Moving forward to the cables I feel like they are also quite solid, and despite being a little on the thinner side and feeling a little plasticky, the tangle-free, flat design screams convenience. There is a built-in mic as well with a one-button remote so the Bolt remains neutral and allows for convenient use with both Android and Apple. Briefly touching on quality the mic is actually decent with clear output and decent sensitivity.
In terms of fit the Bolt is sort of so-so. The body design is well thought-out, with angled bore design which allows for better insertion and thus, better sound and fit. However, when coupled with the included tips, the overall fit becomes quite bad. I have a tendency of immediately swapping tips when buying new IEMs, but after receiving bad feedback on their fit, I decided to try the stock ones on, and OMG they are so bad. Suction is quite large, and the silicone itself is flimsy, which gives a wobbly fit when inserted inside the ears. I don't know how to describe this but they fit similar to those free earbuds you get when you purchase a Samsung or ASUS smartphone. Its bad. Swap them out for a pair of SpinFits or take one from your inventory, any method works but do ditch the stock ones.

---Sound Analysis---
Now this is the part that's exciting. I have so much to talk about so I will give a general summary first. Overall, I would say the Bolts have a weird tonality, which I will explain, but to generalize I would say they lean towards the brighter side of things, with added bass. These should work brilliantly with most EDMs, most Pop tracks, and some Rock. Okay now into the more detailed part...

Treble: This section imho is quite inconsistent for me, which is why I think this is going to be the longest part. I am a huge fan of trebles, and I prefer brighter-sounding gear rather than warm as I can hear more details and thus make the track more exciting (for me). So when I listen to the Bolts I immediately noticed the extension and shimmer. Oh boy does the Bolt strike you immediately with its treble. Upon pressing the 'play' button, immediately my music sounds glossy, with apparent air and shimmer across the board. Initially it blew me away as I thought its going to be another one of those budget IEMs which does treble right, but when the cymbals crash in, I immediately held back. Although the extension is by far one of the best for an IEM under $100, the implementation is poor. Cymbal crashes sound too piercing, and decay is quite long which sometimes could muddle up the whole high-frequency region. Playing "21 Guns" by Green Day shows the Bolt's faults, with the second bridge sounding too muddy with cymbals piercing you on both ears and the vocals suddenly took a huge step back leaving you with nothing but clutter. This, alongside its mediocre detail retrieval, make for a no-no when it comes to complex rock tracks with cymbals crashing all over the place. Moving on to EDM, trying out "No Money" and "Runaway" by Galantis was imo the worst decision I have made when testing these, as their high-pitched vocals generate nothing but nightmare in your ears. Your ears will soothe abit when the song reaches chorus, but for the gaps in between, ugh no. just no. Overall, 5/10 from me.

Midrange: This is going to be the shortest section, as I feel like they have done a good job on it. Pure vocals and instruments like guitar strums sound great, with quality that I feel like is even better than the Shozy Hibikis, which is also known for their midrange. Here the mids sound more dynamic, and although the RE400 still trumps them in this department, they do hold their own. Detail retrieval is nothing to write home about, and does give an immediate sense of resolution when plugging them in. The one reason why I did not say great, but only good for the mids is because I found some faults in the upper midrange. So, I like a little more emphasis on the upper mids, as the songs that I like (AniSong, J/K-Pop) usually rely on the upper mids the most to add that extra energy to their tracks. The Bolt does the upper mids fairly well, but again the implementation is a little flawed as sometimes it can get a little rough/spiky and give you that random pierce when listening to songs like "As if Its Your Last" by BLACKPINK and "Catch the Moment" by LiSA. A minor flaw, but worth noticing for people who are sensitive to this. Overall though, a solid 7/10

Bass: Now this is where I think the Bolt does most things right, with minor faults in the transitions. The Bolt sports bass similar to the urBeats, but is fuller and a little punchier which reduces clutter and muddiness when playing complex EDM tracks with deep, slow bass. Tracks like "Are You With Me" by Lost Frequencies showcase the impressive punch and decay the Bolt has, and going into pop the track "What Do You Mean?" by Justin Bieber again blew me away with how punchy yet smooth the Bolt's bass could be. The minor fault as I mentioned is in the bass-mid and sub-bass transition, as I do pick up a little bit of bleed which gives tracks an immediate sense of thickness and/or stuffiness, and sometimes with tracks that sport both electronic and classic instrument (e.g. bass guitar) the Bolt fails to deliver a smooth transition between the punch and rumble. I am being too nitpicky here, but overall for what it is I give the bass a solid 8.5/10

Soundstage: Soundstage is actually really good, and once you get the right fit with the right tips, these IEMs offer solid soundstage that could rival $50-$100 IEMs on the market. Definition is good, and even though it could be a little hazy around the edges due to the faults I mentioned, it is still enjoyable and I would even game with these (not competitively of course lol).

Transition? what transition?
So this is sort of a bonus section I guess, since I mentioned the word a lot in this section. So I might be wrong when it comes to terminology but transition for me simply means how the sound "moves" in the spectrum, from sub-bass->bass->mids->upper-mids->treble. You can tell if an IEM is tuned well by looking at how smooth the transition is. The rougher it is, the more "disjointed" tracks will sound and you might hear something like bright cymbals but the sound of the drummer hitting the cymbal itself is pushed behind (disjoint in treble->presence) and bass notes having quick punch but suddenly the rumble comes out of nowhere (disjoint in sub->upper-bass). Another scenario would be listening to massive synthesizer extension but very little definition to the synth sound itself (disjoint between treble->presence). This does not apply to the Bolts alone, even some expensive $300< IEMs sometimes suffer from this fault as well.

Since these are really an EDC at its core, I am not going to test these with expensive DAPs or try amping it as it does not make sense and you guys would not be doing that probably. So I listened simply with my 1+5 and I will provide song matchups (YMMV, remember this!):

Strong for:
- Slow Pop (e.g. Rihanna's "Take a Bow", JB's "What Do You Mean?", P!nk's "Just Give Me A Reason")
- Chill / Mellow EDM (e.g. LF's "Are You With Me", Jonas Blue's "Fast Car", Niall's "Slow Hands", Kygo's "Stay")
Weak for:
- Rock (Fast Rock, mainly) (e.g. Dokken's "Breaking the Chains", Linkin Park's "Numb")
- Bright EDMs (e.g. Most of Galantis' songs, JB's "2U", DFA's "Millionaire", Zedd's "Clarity")

Remember these are some examples that I find the Bolt to be good and bat at, YMMV and for you things that are in bad might sound good and vice versa. This is just a rough guide.

I personally think these IEMs are really good value and they do sound much better than what they cost, but if you ask whether these are giant killers or not, I would say no. These will not topple the likes of Hibiki, RE400, or the FH1 any time soon, but they honestly do hold themselves quite well especially in the already very crowded budget IEM market. The build certainly delivers with EDC in mind, and even though I went a little rough on sound, in one of my testing where I just sat down inside the bus for 2 hours and listen to them, I do find them quite enjoyable. I feel like as long as you don't nitpick here and there these are really good for every day commutes. I still do stand by my word that even if this is $10 it should still be bought by the right people, but overall they are okay for what they are. Props to MD for successfully reaching out to the ultra-budget market, and sorry for posting this long for a $10 IEM! I hope you enjoy the read!



Headphoneus Supremus
Pros: Cheap Price
Good Housing Build
Strong Bass
Cons: Cheap Tips included
Poor cable
Recessed Mids
Treble very loose
Comparable to free IEMs/Ear Buds

Massdrop has had some very strong collaboration products with major industry players over the past few years in the audio arena, so when Massdrop announced their latest collaboration with Hifiman, I was ready to jump on board -- especially at the offering price of $10!

This drop actually ended up arriving before the estimated ship date by several weeks, so that was pleasing.

I was definitely skeptical about a $10 set of headphones from a company known to sell headphones from $500 to over $10,000. But at the same time, I never heard any of their IEMs before, so I was up for anything, and at the asking price, it was hard to turn it down.


So the item came in a very basic box along with 3 sets of cheap silicone tips (Small/Medium/Large). The cable is non-detachable and is a flat-wire type, which I really dislike in general. For example, the ones that Audeze uses on their portable Sine and iSine headphones -- I really do not like. Hifiman takes my dissatisfaction of flat cables to a whole new level though. This cable is just "flat" out awful.

It does have a mic built into it but I have yet to try it.

The IEM housing itself is an attractive aluminum shell that is simple and elegant. It's also small and lightweight, and fits rather easily in my ears. These have to be worn cable down, as the driver is angled to fit that way, and cable, again, is not detachable.

hifiman bolt - raw FR.jpg


My first impressions putting these on were something like... OH MY GOSH! THAT BASS! The bass slams and is monstrous if you get a good seal. But everything else is utter garbage. The mids are very recessed and treble is extremely loose. Many people have complained of a "tinny" sound, which I can also hear too, though not as badly as people may make it out to be.

The IEM is L-shaped with major focus on the bass and low mids end. The above MiniDSP EARS measurement I made definitely shows that.

The bass is exaggerated while the mids begin to slope very far down and become recessed in the main vocal range. The upper mids look like they start to behave like one would expect but then treble is completely rolled off with a slight bump around 16K.

Soundstage is medium width and instrument separation is average. Detail and clarity is severely lacking on this IEM, and they tend to sound muddy in many tracks.

Bolt - THD.jpg


While I wasn't expecting an exceptional audiophile IEM with this price, I was expecting something similar to other Hifiman headphones I heard - in terms of sound signature and tonality. Instead, this thing reminds me more of a generic consumer-sound that is worth about $5-10. Many of the packaged ear buds and IEMs that come with phones and DAPs sound better than these.

This is quite a disappointing addition to the Hifiman family unfortunately.

Finally, a comparison to my current budget king, the Tin Audio T2:

Bolt vs Tin T2.jpg
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Reactions: ssnjrthgr8
You can wear it over ear and it actually provides a better seal and improves the clarity of bass. Also this thing has a massive driver flex to it, crinkles like crazy when you put it in the ear
@ssnjrthgr8 I wasn't able to wear it comfortably over-ear unless I swapped driver sides. Yea I forgot to write about driver flex in my review. It was the worst I've ever experienced.


100+ Head-Fier
Pros: Cheap
Aluminum housings feel well built
Relatively clear midrange
Nice tactile feedback on call answer/end button
Powerful, and well-extended bass
Cons: Tips aren't the best
Detail retrieval is poor
Cable feels very weak and retains it's shape
Fit is poor when worn down
Somewhat hard to drive
V-shaped signature doesn't work well with all music
I've never been one to make pretty intros or anything so let's jump right in...

: I prefer a neutral sound signature with a couple dB increase to sub bass response and a slightly warm lower midrange. I tend to dislike any midrange recession. I have been in this hobby for a couple years and have tried and owned a plethora of headphones and IEMs. A large soundstage matters less to me than detail retrieval and instrument separation. I purchased these from Massdrop for full price and am receiving no compensation of any kind for this review. All of my opinions are just that; opinions. As always, YMMV.

Pictures: The few pictures I took can be seen here. Sorry I don't feel like spreading them out through the review. You can see the packaging, the Bolt, and a couple pictures comparing size to other popular (albeit more expensive IEMs).

Packaging/Accessories: The Bolt come in a very basic box. Considering these are $10, the minimalist packaging is fine. Inside the box are two baggies. One has the Bolt IEMs and the other has spare tips. The only tips included are single flange in S, M and L. The included tips are okay but a bit stiff for my personal preference so I switched them out for UE tips after about 10-15 minutes of listening. No case is included.

Build Quality/Cable/Fit: The housings themselves feel acceptably well built and I can't expect any more for the price. The flat cable feels, looks, and behaves almost exactly like the one on the Logitech UE500vi. It definitely seems to be the weakest part of the IEM. If I was going to be using these regularly, I would definitely put them in a case to help keep the wire safe. There is a microphone and an answer/end call button on the right side. The button has a solid, satisfying click to it. It requires enough force that it won't be bumped accidentally and that you know when you've pressed it. The cable retains the bends Wearing them down, I was able to get a decent seal and they were comfortable. However, I could not get a good fit this way; they kept wanting to fall out after a short time or with a very light tug. Worn down, microphonics are present. Definitely noticeable and annoying, but it won't keep you from listening to your music. I switched to wearing them over-the-ear and everything improved. Comfort is good, they don't want to fall out, and microphonics are nonexistent.

Sound Overview: I used Tidal for all of my listening. For my first impressions at home, I plugged the Bolt straight into the SE headphone out of my Soekris dac1541. The majority of my listening has been at work where I had the Bolt plugged into a HeadAmp Gilmore Lite mk2 connected to the line out of an Oppo HA-2SE being fed from my work laptop. They seem to require more power to drive than many IEMs but quite not as much as the UE500vi or Pinnacle P1. They should be able to be driven to reasonably loud volumes from just about anything, however they seem to like a dedicated amp. Overall, the Bolt has a V-shaped sound signature: heavily accented sub bass and bass, lower-midrange recession followed by a rise in the upper midrange that continues into the treble.

Bass: Holy cow this thing hits hard. IMO, this can be considered a basshead IEM. The sub-bass response drops off a tiny bit below 40Hz but I can easily hear it all the way down to 20Hz at normal listening volumes which is something I can't say about many other IEMs or headphones. The bass lines in Work by A$ap Ferg and Rack City by Tyga are downright intoxicating. The Bolt seems to be right at home playing rap or other beat-centric music. When moving over to rock/metal, the bass guitars and drums can be a bit overpowering. When lots of stuff is going on, the bass seems to lose definition and feels a bit slow. The bass seems to lose a little of its power when being driven by the headphone out of the HA-2SE or the Apple Lightning Headphone Adapter vs the Gilmore or dac1541.

Midrange: After the intensity of the bass, the midrange takes a step back. My first impression of the midrange was actually quite good. I thought it sounded very clear for a v-shaped IEM at this price. The lower to mid midrange sounds recessed to me and makes a clear separation between the bass and midrange. Electric guitars and many male vocals seem to have much less weight to them than they should and can sound a bit off. Male vocals can come across as a bit disconnected from the music and sound hollow. After the lower midrange lull, the upper midrange starts to pick back up again. Female vocals tend sound better than male vocals but still lack a little weight to them. Once again, the Bolt sounds better with beat-centric rap or pop music. Vocals come through a bit cleaner with this type of music than rock, or other, busier music.

Treble: This is where things get really bad. To my ears, it sounds like the frequency response continues to rise past the upper midrange into the lower treble. There is a very large peak at 5kHz-5.5kHz which can bring out a tinniness quality to the sound. This can also make female vocals sound a little metallic with an unnatural timbre. Listening to frequency sweeps, I can hear other peaks at 6.5kHz, 7.5kHz, 10.5kHz (small), and 12kHz (large); it sounds like there's a kid constantly playing with the volume knob on my amp as the frequency changes. The treble does extend well, all the way up to where I can't hear past 17kHz. The treble overall is very peaky and sounds a bit unnatural. The Bolt is pretty sibilant to my ears unless I'm listening at fairly low volumes. Not only is the treble pushed forward, but it's not very detailed. Cymbals get lost in one another and it's hard to tell multiple hits apart.

Detail Retrieval: Poor all around. Considering this is a $10 IEM, this is somewhat forgivable but it still bugs me. Simple songs like many modern pop or rap songs come through well but sounds start smearing together when a lot is happening at once.

Soundstage/Imaging: Soundstage is okay but doesn't really stand out. Sounds are in my head for the most part with the exception of some of the balls in Bubbles by Yosi Horikawa. Listening to Tarova by Snarky Puppy and Bubbles, imaging seems pretty good; especially for the price. Since I know Tarova fairly well, I know where instruments should be located and the Bolt does a pretty good job at recreating that.

Conclusion/Other Thoughts: For the price, these aren't bad. The key here is the price. IMO, its three biggest flaws are sibilance, lack of detail, and fit. The sibilance is kept at bay in some tracks but others it's almost unlistenable; kind of like a stock HD700. The lack of detail is something that bugs me in all but the simplest of songs. The fit is a bit odd with the stock tips. The tips are a little too stiff so they want to push the housings out of your ears. I can also see how the housings could be a bit large for some people even though they fit me well enough. Vocals sound good in simple pop and rap songs but quickly go downhill when other instruments are added and the driver is asked to do a lot at once. The midrange is surprisingly clear for how far forward the bass and treble are.
I wish I knew where my Mee Audio RX18P is so I could compare the Bolt to them. They are my current favorite for $10 or less and I think the Bolt could definitely give them a run for their money.
After going back through the frequency sweeps two more times, I still hear the treble peaks in all the same places.
I wonder if little, stick-on filters, like those used in the nozzle of the Hifiman RE600S V2, would help tame the treble a bit and reduce sibilance. I cannot seem to find the extra filters that came with my RE600 at the moment so that may have to come at a later date.

Thank you for reading my review!

15AUG2018 EDIT: Bottom line, would I recommend these? No. If you can afford a little more, you should definitely spend it. There are some really great options out there for less than $50. If you absolutely cannot spend more than $10 on something, these should be considered. If I hadn't taken price into consideration, these would have received a 1.5-star rating.

Test Tracks Used: A list of some, but not necessarily all music I listened to for this review. I wanted to keep this at the end because it is long.
  • Stevie Wonder - Superstition
  • Yosi Horikawa - Bubbles
  • Slipknot - Snuff
  • Bear McCreary - God of War
  • Snarky Puppy - Tarova
  • Graham Colton - Best Days
  • Beartooth - Beaten in Lips
  • Ed Sheeran - Castle on the Hill
  • Uncle Kracker - Drift Away
  • Maroon 5 - Sex and Candy
  • Rage Against the Machine - Take the Power Back
  • You Me At Six - I O U
  • Dead Can Dance - Song of the Stars
  • Halestorm - Vicious
  • The Amity Affliction - Ivy (Doomsday)
  • Asking Alexandria - A Prophecy
  • Chelsea Cutler - You Make Me
  • Dagny - Used To You
  • Tyga - Rack City
  • A$ap Ferg - Work REMIX
  • Gryffin, Katie Pearlman- Nobody Compares To You
  • Jason Lancaster - Hey Jude
  • Sam Hunt - Take Your Time


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