Headphoneus Supremus
Penon Serial the triple dynamic allrounder
Pros: - Musical
- Natural Timbre
- Engaging Bass
- Romantic Mids
- Neutral/relaxed treble
- Wide Soundstage
- Good Imaging capabilities
- Design
- Accessories
Cons: - Microdetail (still its some of the magic)
- Hard to find Cons
Penon Serial the triple dynamic allrounder


This is my first Penon product if you do not count ISN, I bought it with my own money. All impressions below are my own subjective thoughts after a few months of use.

Description from the Penon website

Medical grade resin cavity, light and beautiful, comfortable to wear, no strange feeling in contact with the skin.

Semi-transparent black shell, the panel is made of stabilized wood red, blue, and green 3 colors mixed

Made by hand, the earphone shell is solid and more durable.

6mm pu diaphragm for high frequency

8mm titanium-plated for middle frequency

10mm biological diaphragm for low frequency

Resin shell, stabilized wood panels

3-way crossover, 3 tubes

Stainless steel nozzle


Brand: Penon

Model: Serial

Driver: 3 Dynamic Driver

Impedance: 18 ohm

Sensitivity: 103dB

Frequency response: 20-20kHz

Connector: 2Pin 0.78mm

Plug: 3.5mm audio, 2.5mm balanced, 4.4mm balanced

Cable: 8 shares OCC & silver-plated Mixed Braided

Cable length: 1.2M


18 months warranty

Penon has quite a big lineup of IEMs and cables, and continues to make new IEMs and cables every year. The last IEM launch of them being the Impact priced 2500$ and from first impressions competing even higher in price. This is something that is often the case with their releases, they almost always compete with sets more expensive.

Penon FAN $139 - 10mm Single Dynamic Driver
Penon FAN 2 $279 - 2x 6mm DD bass driver + 2 BA Drivers for mids and treble
Penon Globe $339 - 10mm DD doing low end + 2 BA Drivers mids and Highs
Penon Impact $2499 - 10 BA Sonion BAs and ESTs
Penon Legend $1299 - 13 BA Sonion and Knowles with tuning switches
Penon Orb $249 - 10mm DD + 1 BA
Penon Serial $299 - 3 DD drivers
Penon Sphere $159 - 1 BA
Penon Volt $799 - 10mm DD + 2 BA + 4 EST
Penon Vortex $219 - 10mm DD

About me and my gear used for the review

My audio preference is neutral with sub and mid bass boost, mids can be forward but not too much. I can also handle some treble spikes if it's not excessive. I am a believer in having different tuned IEMs for different genres or moods instead of chasing the single perfect one.
Main music genres I listen to are Metal, Electronica, Jazz, indy rock/metal, R&B, Pop. I am a music lover, and can listen to almost all the genres out there. I have been into music gear since the mid to early 90s, gifted some big speakers at an early age. Then moved more and more into headphones with the Koss Porta Pro and a Sony DiscMan and MiniDisc.

I have tried playing many instruments over the years from piano to sax and have a feel for what's a natural tone, but not a talent in playing. My wife has also played many instruments from string instruments to wind while has the talent part I lack.

My current standard in IEMs is SA6 and Penon Serial. One all BA with near perfect tonality for me, and the Serial with also a near perfect tonality for me. That is also the IEM getting reviewed here, so a little spoiler.

Gear used in the main rig is Topping E70 DAC together with the Topping A90 Discrete headphone Amp. I also have a Schiit Lokuis I can swap to if I want to do a little EQ.

I have also used the Feliks Audio Echo, one of the more silent OTL amps.

Portable gear has been Tempotec Sonata HD II Dongle, Hiby R3 Pro Saber 2022 DAP, Quidelix 5k DAC/AMP and Xduoo XD05 Plus DAC/AMP.


What the Penon Serial is:

The standard in IEMs around this bracket is Hybrids or in rare cases a single dynamic driver IEM. The Serial uses 3 dynamic drivers of different types and size, with crossover so each DD has different parts of the frequency response to do.

The low end is handled by a 10 biological diaphragm, the mids with a 9mm titanium-plated diaphragm and last the 6mm pu diaphragm doing the highs. The magic part here is that all the drivers are dynamic drivers and masterfully put together so If you asked me I would have believed it is a high end single DD IEM. A part of this working so well is the tubes from each DD deliver the sound straight to the nozzle.

The face plate is stabilized wood and not one Penon Serial looks the same since they are handmade and painted. The resin is semi translucent and with some lighting you can see some of the magic inside.

It has a safe form factor with medium size shell and medium length nozzles, this should sit well in most ears.



Package and accessories

You get the yellow product box, cable, cable pouch, 3 sets of tips(S.M.L), leather strap, Blue storage box with zipper, little brush, shirt clip and the IEMs itself. Not too shabby if you ask me.

The case is just the right size and can fit the IEMs with cable and a small dongle, zipper is in metal and to me makes me afraid of the cable coming in between. The color is also quite striking, but blue is the color that Penon goes for with their storage cases.

The included tips are of good quality, from wider bore to smaller. If you don't have a tip set you love you should be happy here without the need to buy anything. Personal favourite is the green one.

Penon CS819 is the cable itself and is a very good value and performing cable. OCC and Silver Plated Mix. This is one of the cables I recommended when in need of a cable under 50$, it's soft and flexible. Great weight not being too heavy or too light, the connections and splitter are good quality. It sounds great, so when in need of a cable that's natural sounding not changing the signal.


This picture is taken from Penon listing, since I never took a picture of it all.

So how does it sound

Natural, bold and sensual is the first that comes to mind. The sound is coherent with no gaps that makes you want more, when you put on any type of genre it will usually sound great .

I have different types of headphones or IEMs for different purposes. The Penon Serial breaks that for me. Yes maybe I would have wanted a little more of that or that for something, but the thing is nothing is wrong or lacking so I tend to not have that thought. While my favourite genres on the Serial are Darker Metal, Prog Metal/Rock, Melodic Metal and so on.

I had a talk with another reviewer(Tony), he had a good analogy for the Serial: it is like the good big vintage speakers. And I 100% agree with this, the big speakers with 12-15 inch woofers. Not the most technical sounding speakers compared to today's standards but perhaps more musical and thick sounding. Do not take this out of context and think it lacks details, it shows everything with good detail, soundstage and imaging. Still some other sets will give you better microdetails if that's your thing.


First off what is Timbre?
From the Wikipedia:
The Acoustical Society of America (ASA) Acoustical Terminology definition 12.09 of timbre describes it as "that attribute of auditory sensation which enables a listener to judge that two nonidentical sounds, similarly presented and having the same loudness and pitch, are dissimilar", adding, "Timbre depends primarily upon the frequency spectrum, although it also depends upon the sound pressure and the temporal characteristics of the sound"

First minutes of trying a new set of gear, what I always listen to is how natural and musical it sounds. Much of this goes down to how I perceive the Timbre.

Penon Serial has a very natural sounding timbre, instruments sound very close to what they do live. It gives a little extra warmth making it lusher and more romantic. So not 100% right, and I like this approach.

It reminds me of some wood headphones that also have the same type of timbre.

The timbre is often more correct to me in DD drivers, so here we get 3 drivers all DD. This does its magic making them sound coherent from the low end to the high end. BA can also do a good job here and sound natural, but here again is more easily done in all BA IEMs rather than hybrids.

Details, Soundstage and Imaging

As mentioned before this is not the most detailed monster out there, it has drawn a line where you get good details but not too much where the experience of the song is ruined by a bad recording.

This means it also pairs well with music that is old and not up to today's standards. With good recordings I can adore technical gear showing every nook and cranny. Love the headphone ZMF Verite for this, while at the same time it's not headphone where I put my library on shuffle and enjoy. This is where Serial is a good companion.

The soundstage is presented more forward than most single DDs IEMs, having some nice depth and a little outside your head. What is the most impressive is how wide it goes , especially far out to be an IEM. While someone is always going to disagree, the soundstage is a subjective impression that differs from person to person . This is still an IEM and not an open headphone with a vast soundstage.

As for imaging there are no gaps I can notice, I do think that this is a place where IEMs often do it better than headphones. Many headphones will have some dead zones where the image is disappearing. While I mostly do my tests with music, I also play FPS shooters. The soundstage and imaging does a fine job pinpointing where sounds are incoming from.

Michael Jackson with Thriller is a good and fun sounding track to test soundstage on. Good separation of the sound and different depths being shown. Feels almost like a binaural recording.


Yosi Horikawa with Bubbles is also a masterpiece for testing soundstage and imaging.
It's also very technical as much is happening at the same time here, Serial in my opinion does it as a champ.



The bass is elevated but not a basshead amount of bass, I would say it has struck a good balance between fun and not overpowering the mids. This comes back to the 12 inch vintage speakers, the bass has a large sound. Not the fastest and not the slowest, it's in a good middle ground with some good sustain and decay. It can easily hold up with the speed in Psy Trance and other fast electronica genres.

If I would say a little negative it's that I would have preferred a little more sub bass, while the mid bass are probably what I find to be perfect amount and balance. Most IEMs coming out sound to lean in mid bass, specially the Harman tuned ones. Harman target while having a good sub bass rumble, lacks emotion and attack. I would say the soul of music is in the midrange and the mid bass, it's what makes you wanna dance.

In case you are a basshead this is not the amount you are looking for, but it has the definition and bass technicalities that might set your other bass head IEMs to shame. Especially if you EQ the sub bass up a few dB.

Its very detailed bass and sounds very natural, check out some killer bass lines from Victor Wooten and you can see what I mean.

Angel by Massive Attack
Good sub bass slam and it digs deep into the lowest frequencies, could have wished for a few more dB at the lowest notes. Still I have other IEMs for this if the perfect sub bass is needed. I do think it handles it very right overall.

Moth - Dyacide remix by Epsilon, Dyacide
Immersive ambient electronica, with a fast rhythmic bass going also having a heart pumping sub bass in the back. This is a track I personally hate on slower IEMs or the ones who don't have enough mid bass slam. Serial can easily follow the rhythm give me pure satisfaction here. Great track overall, just be sure to not push your volume too much as you will get tempted on the Serial.


So What by Miles Davis
Well renowned track, the Double Bass is played through the whole track. Here it's not too forward in the mix, with a basshead IEM this arrangement sounds wrong to me. With the Serial it hits just right showing good bass separation with just the right amount.


First off, if we say that the mid Frequency is from 300 Hz to 4,000 Hz it's easier to understand what I'm expressing in this part. Mids are where vocals and almost all instruments are, around 80% of the music is within the midrange. Many say that the soul of music is in the midrange making the success of a set of gear. I do agree to some part with this, it's also where too much makes the sound fatiguing or shouty. While too little can make the sound boring.

The midrange is very much to my preferred liking with a small forwardness that makes both instruments and voices come alive.

The lower part of the midrange is fairly neutral, maybe some small warmth.
The upper midrange has some extra energy, giving some good energy to music. This combo works very well for me making vocals not shouty or tiresome, while giving some warmth to the sound signature. Just borderline increased so it's not fatiguing with brighter jazz or rock.

Stretch your Eyes by Agnes Obel
The fullness of Agnes' voice together with the Cello is very intimate and magical. I do feel the tonality in Serial shows the song very spot on.

Trade it for the Night by HAEVN
Very good track and Marijn van der Meer has a beautiful and hypnotizing voice. This is a goosebump song on Serial and lets the midrange qualities flourish.


About Today by The National
One of my favorite tracks, I have played this on repeat over and over for years. It's both a sad and intimate song, the cello playing in the background giving many emotional feelings. This is one of the tracks I can notice that male voice is perhaps a small amount forward with the Serial, still as mentioned its minimal. I can listen to this track forever with the Serial.



Can first start with saying that the Serial is sibilance free, it has frequency dip from 4k to 8k making it quite relaxed. While still keeping some good air for the upper harmonics. Would call it a relaxed treble with good extension.

Humming by Portishead
Another on Head-fi recommended my try this some years ago when I was testing a headphone for how fatiguing the treble is. It has lots of weird elements, and sounds almost trippy. There are lots of unpleasant sounds that are shown if the treble is too forward or harsh. The Penon Serial does this as a champ. Personally I can take much treble but this track with the IEM Tipsy Ttromso is almost painful in comparison.


Claire de Lune by Kamasi Washington
This is a complex track with loads going on, this also tests brass instruments from the midrange. While everything sounds very right this is borderline too much and a faster IEM does this track better. Still it shows good separation of the instruments, and is not that slow that it smears the sounds together. This is also a track where forward midrange can push the Tenor Sax over what's pleasant. Not my favorite track on the Serial because of what is mentioned above, this impression is also due to my favorite cable that pushes the mids a little forward.

Air performed by Anne Akiko Meyers on violin.
Air is breathtaking here, the violin feels alive. And the airy treble is clearly present, I'm not a person who listens much to classical music. Still from what I see as a perfect representation with the ZMF Verite, the serial does lack some detail and airiness. But this approach is not wrong and is still tastefully good, where you just don't pick apart every nuance.

Gear and cable synergy

I have tested the Penon Serial with portable dongles, portable amps and desktop gear. It scales very well with higher end amps like the Topping A90 Discrete. I have a preference with cleaner sounding amps on the neutral side over warm or dark gear together with Serial. It is harder to drive than many other IEMs but all the dongles I tried have done it loud without getting anywhere close to halfway in volume.

One unusual pairing that has been quite fun is the Feliks Audio Echo tube amp, this amp is very silent and had sound on the more neutral side to be a OTL.
This combo gives even bigger lushness to the sound and makes the bass hit even harder and bolder, very fun with electronica and dark metal music.


As for cables I have tried the DUW-03, Penon Mix, ISN C2/S2 and NiceHCK Silver Cable. Favourite being the ISN C2, while the DUW-03 is a perfect companion and a clear upgrade cable when going from the stock cable. While the Mix also is similar it has some extra treble energy compared to the DUW-03.

My favourite ISN C2 gives some extra fullness to the sound similar to what my tube amp does. You also get modular connections making it more versatile with DUW-03, Mix and C2.

The changes are small and if it's because it's placebo or not doesn't matter for me.




And yes this is not a dynamic driver and not the same price group. What makes me put them into the review is that it's also a multi single type driver, 6 BA drivers with a nice tonality that many know about. It's also one of the few IEMs I own.

The SA6 has a more neutral sound, with a more clean clinical timbre that is mainly due to the BA drivers. Since its BA it's also a very fast IEM, and never really gets confused with fast technical songs.

Serial is more musical with more body to both the low end and mid range. Treble is more refined and forward on SA6, airiness is similar.

Soundstage is wider on Serial with around the same depth on both. Micro detail in the imaging goes to SA6.

They are very different but at the same time share a a clean unobtrusive sound, one being more on the cold side and the other on the warm side.

Penon FAN 2
Hybrid consisting of 2 DDs for the bass and 2 BAs for mids and treble.
This is a more neutral IEM with less warmth to the bass and mids compared to the Serial, as for treble detail and energy they are not far off each other. While the BA does make the timbre be closer to the sound of the SA6 in the mids and treble.

The low end is faster and less boosted in the FAN 2, while the Serial has harder sub impact and perhaps better note separation in the sub bass notes. The Mid bass is the other way around with more slam in the FAN 2. Both do the low frequencies great.

Mids are similar in how forward voices and instruments sound, while the timbre is different. I like both and would say that the Serial is more romantic while at times with brass it can get too much that will not happen on the FAN 2. Also a note on the deepest voices of male, there is some forwardness on the FAN 2. It's not unpleasant, but on some tracks can seem unnatural in comparison to the Serial approach.

The upper mid range is actually a little relaxed on FAN 2, they have the same amount of treble extension. Maybe tipping my hat off to the FAN 2s treble, this might also be due to the fact that the FAN 2 is more technical with its BAs.

For details the FAN 2 is the winner, but not by much. It shows more micro details, still less than SA6 does. As for soundstage I would say the Serial is wider while the FAN 2 has perhaps a deeper presentation. Both are great in my book in the soundstage.


Penon FAN
This is a fairly new IEM for me and much cheaper than the Serial. It's a single 10mm DD driver. This has a more v shaped sound, it still has a good mid presentation that is just not as present as the lows and highs. I personally like to have a V shape sounding IEM to dampen the mids on some genres.

FAN has more sub bass and mid bass than Serial while the bass notes are more refined on the Serial. As for speed they are close to the same.

Mids are more recessed on FAN, both voice and instruments gets shadowed some by the bass and treble. Some small bleed in the lower mid bass, but it is minor.

Going into the upper mids and lower treble the FAN has more energy and is increased over the Serial. The presence region is a make it or break it part of the sound, I prefer some extra bite while some others do not. The Serial is much more safe here.

FAN has an excellent upper treble also well extended. While the treble in the Serial is more pleasant and smoother.

Both imaging and soundstage is a win for the Serial, they are quite differently made and priced so it's not a shock.


Truthear HOLA
A small comparison with the newest entry level hype IEM. Different league. HOLA is less detailed, leaner sounding in both the mids and bass. When looking at measurement of both the difference shouldn't be as different in the bass notes. Still the HOLA is softer and less defined in the low end, and lacks some mid bass thump. Treble extension while good on the HOLA is still less detailed than Serial. For people who prefer a leaner and softer presentation the HOLA is great, especially for the price.



If you read the whole review you might have noticed I do have a love for the Penon Serial. While I can nit-pick and say that I would have liked more microdetail, that would have changed the approach of the sound. It has a pleasant line where it's detailed and relaxed enough to not make music a task to listen to.
It has a safe tuning with enough low end to please most, even some bassheads. The mids are romantic and give a full sound. The highs are slightly relaxed and for most people pleasant and engaging.

I would call it a genre master, I can put my music library on shuffle and enjoy whatever that comes on.

If I were asked to take one IEM with me on a 1 year trip this would have been my choice. I also bet that it is one of the safest sets when someone is asking for a recommendation.

It's not an IEM for the ones who need ultimate resolution and capabilities, but for the music lover.

Going back to the start, this is a bold vintage speaker packed into a small IEM and I truly recommend it.

Last edited:
@Alino would love to try it one day, not many places or brands to try out in Norway. Need to thrust others on the web and blind purchase. And thanks 👍
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Reactions: Alino
Best review to hit the front page in a while! Congrats :beerchug:
Excellent review and TOTALLY agree 😎👍

And this is all about music, not sound.... 🥰😉


Headphoneus Supremus
Next level musicality
Pros: -Bass presence, layering and fullness
-Mids presence, layering and fullness
-Natural dense timbre
-beautifuly balanced warm W shape tonality
-wide lush male and female vocal
-thick yet well articulated layering
-good enough transparency
-smooth non fatiguing
-heavy note weight and dynamic
-wide holographic soundstage
-excellent all arounder
-dark treble that doesnt lack in details and nuance
-excellent accessories
-good construction with appealing look
-great price value
Cons: -not the cleanest sound
-not the sharpest resolution
-not the most extended and sparkly treble
-not for treble head


Penon is mostly known as an audio distributor and cables maker, yet they begin to release earphones years ago. Their IEM like the Vortex single DD or Globe hybrid DD+2BA have a solid fan base. It seem the Serial I will review today is quite appreciate by audio community too.
Priced 300$ (but on sale right now at 270$), the Serial is a triple dynamic drivers earphone using 10mm biological DD for low, 8mm Titanium DD for mids and 6mm PU DD for highs.
Since i'm quite a fan of Unique Melody 3DT, my curiosity drive me to contact Penon for testing this IEM, so, these doesn't come out of the blue but are lucid independant decision driven by pure audiophile curiosity.
Now, let see in this review if Penon achieve a cohesive tuning with all these exotic DD and if it worth the price tag too.


Model: Serial
Driver: 3 Dynamic Driver
Impedance: 18 ohm
Sensitivity: 103dB
Frequency response: 20-20kHz
Connector: 2Pin 0.78mm
Plug: 3.5mm audio, 2.5mm balanced, 4.4mm balanced
Cable: 8 shares OCC & silver-plated Mixed Braided
Cable length: 1.2M
18 months warranty



What hit me first seing the Serial is how small they are for triple DD IEM, about 1.5times smaller than UM 3DT for example. After this, it was how beautifull the back colorful stabilized wood panels were, this is arsty craftmanship at it's best, as I like it. When it come to the shell, its made of medical grade resin plastic, it feel sturdy and it's very smooth and light too. The organic shape is very compfortable, i don't feel it as if it were ''part of my body''. Isolation is above average and sound leakage minimal. Nozzle is made of metal and feel durable too. 2pin connector are solidly embeded in shell body. Their no low quality control here, everything feel flagship as we can expect with a 300$ IEM.



Now when it come to packaging, their nothing to say apart the fact i was worry of number of accessories seeing how small the box was. But then, i was overwhelmed by the generous amount of whats include. Don't judge anything by it's size! Here we have high quality carrying case, not a basic one, something durable and elegant. We have a cable leather pouch and holder, cleaning brush and clamp cable holder. 6 pairs of good quality ear tips and, just wow, this high end balanced cable.


This cable is the Penon CS819 OCC & Silver-plated Mixed Braided 2.5mm balanced cable and sell for 50$ on their Ali express store. Its well built with sturdy connector. Its smooth and flexible and I appreciate it doN't have ear hook for more versatile use. It doesn't drastically affect sound rendering, perhaps add with of warmth and timbre density, yet keeping resolution, transparency and dynamic scaling intact. This might become one of my fav cable in fact. You can choose between 3.5mm single ended or 2.5mm-4.4mm balanced models. Very impressive.

All in all, this is excellent accessories that put to shame lot of pricier IEM. Respect, Penon!



The Serial offer a dark W shape signature, where bass and mids trigger all attention. We can call it bassy L shape too, or even balanced U shape due to sub bass emphasis. Its the type of musicality that is thick as a whole and very cohesive, yet feel open and widely layered. Nothing sound like the Serial, yet when you listen to it you feel at home, it's weighty in its dynamic yet laid back in treble. But don't be scare of the dark here, since everything sound full: bass, mids and treble are all meaty with this unique sens of holographic layering, resolution isn't lacking but highs are soften and don't have spike in brilliance and air region. Once you enter critical listening mode, the Serial are highly rewarding in details and nuance, but doesn't force it with fake clarity boost.

Those are for bass lover first, both in quality and quantity, the low end is phenomenal in how fully extracted and layered it felt. These are one of few IEM where i can focus on bass player and see it's beefy resonant bass line as if I was at it's side. So we have a hint more sub bass boost but this doesn't stole slam effect, which have warm weighty punch, but doesn't magnify kick drum presence and texture, here, it favor the texture of bass instrument from acoustic to electric bass to synth. This aren't exactly basshead too, since it's too well balanced and cohesive with rest of spectrum for that, yet, when the cello or bassist go solo in a band, you'll understand how talented the performance can go, since it dig down to 20hz, offer vibrant well controlled rumble or resonance, have dense body full of natural air and lead attack grip that doesn't create timbral imbalance. I can't rave enough about the bass response of these, since it's a versatile one that can benefit wide range of music from jazz to classical, to electronic to soul to r&b to rap etc. It find the sweet spot balance between sub boost, slight mid bass boost, slight dip in high bass then extra boost in lower mids, chunky is the result and the use of 3 dynamic driver avoid muddiness due to excellent layering capacity. No doubt the Serial would be dream IEM for bassist that wanna monitor their playing in a band, i need to underline again how well its physicality is extracted, it's presence is not due to texture boost but low harmonic tone boost. The timbre is buttery, colored with hint of liquid warmth and palpable vibrancy. Is it the fastest? I don't think so, is its ultra clean in separation? Nope, its more about transparent layering and kick drum is dark sounding. So, only music that i would not suggest the Serial is perhaps for very fast rock or jazz fusion that have one or 2 pumped up drummer, so, while it would be god to monitor bassist, the lack of texture and kick drum definition as well as tamed percussion energy will be problematic for drum player.

Since I praise so much the bass, mid range should be underwhelming right? It should take second plan, but this is the magi of Serial, the mid range is as addictive and captivating as the bass, as full, wide and thick in presence too yet with great transparency for proper layering. You know when you can't wait your singer to begin to sing in a track cause you know it would be so musically rewarding? This is it with the serial, and to my ears it trigger this eargasmic experience both for male and female vocal. What is impressive too, it's the fact pina gain isn't too high, so it's not vocal presence that is forced at you, shot at you with impatient urgency, its blossom widely and bigger than nature projection, its not compressed vocal that are stock in middle of instrument, nor veiled by bass bleed, it unwrap fully and take all the stage in openness, and it's smooth, lush, dense. Female vocal are free of sibilance, with hint of extra low harmonic emphasis that benefit breathyness and thickness, inflicting even more on emotional response of listener. Madeleine Peyroux sound as wonderful as Timber Timbre. So, to some extend, due to soften upper mids that can affect slightly definition edge of sound envelope of instrument like piano, the Serial favor woodwind instruments and vocal, and let me tell you that saxophone sound freaking marvelous with those, listening to Prism Quartet is intensely beautiful, even if more than on sax play in same range, the layering doesn't mix up and notes are fulfill with air and color nuance, its smooth yet rich and free of this over textured presentation that affect naturalness of instrument tone as well as can distract us from plain musical pleasure. And for piano, it's not bad since note weight are felt, resonance is open, yet definition of each note is a bit darken, so the Serial are just not end game for piano lover, yet might be for vocal, sax, trumpet, cello and even violin, since this time, its lush and have hint of texture bit that help attack articulation without going overly abrasive and raspy.

Perhaps I worry you with my introduction to treble, that i call slightly dark but be reassure, it's not overly so and very rich and full sounding, here it's well balanced and cohesive, the Serial don't want you to know their 3 different dynamic drivers hide in its body by overly emphasizing texture variance of their drivers diaphragm. So, we have a smooth, natural sounding treble with just a hint of extra snap so snare and brilliant percussion can have enough sens of energy. The details are there, but not in front of bass and mids, which tend to hook the attention more, as it should be unless you go critical listening way. These aren't analytical at all, nor what i would suggest for treble head, but the highs have beautiful resonance that are very realist and life like, you'll hear richness of brush strike in its density more than texture, so can we call the high holographic and hint euphonious, yes, these 2 exotic words describe well what I hear. These are fatigue free highs with good sens of dynamic and bodied presence, high pitch instrument doesn't feel tamed but well control in loudness amplitude projection, should it be piano, violin or female vocal their no shoutyness, no harshness, no splashiness. And about splash cymbals, it doesn't feel artificial scooped, just a hint soften in sustain release so the resonance will be there but gently blurred. If i go nit picky, ill say treble lack air, sparkle and extension up to 20khz, and extra 15khz spike for brilliance and extra snappiness would transform the Serial into TOTL IEM. Add an EST to this and you'll enter end game territory. So, some instrument will feel a bit lacking in proper presence authority and texture like electric guitar and clavichord, for ex, even in chamber orchestra of baroque classical, the clavichord will tend to sound more distant than violin, piano and cello. Nonetheless, like bass and mids, the treble is a very versatile one that will benefit more music genre due to it's charming fatigue free balance.



Spatiality is very wide and have good tallness, we have a full mix of stereo and center stage spacial cue, but it's not the cleanest or airiest openness since their no scooped dynamic zone, and space is fulfill with wide transparent sounds layers.

This permit a good layering separation, but less precise and accurate static positioning. It's not bad per see, just not sharp enough in resolution for clean separation definition...a bit like, being to near of your sound system you know, to get fully immerse in thick musicality, to get goosebumps instead of cerebral enjoyment.

So, while i consider resolution rich in colors nuance and instrument presence fullness, i don't consider the Serial king of technical accuracy, precision of definition or micro details generosity. My real qualm would be lack of proper sound info above 10khz.

Attack speed is good, but not balanced armature or even planar fast, it's not very edgy yet not out of control. The edge is hint blunted but in an appealing euphonious way which make result rounder than edgier. Its still above average and im impress that transient response of 3 drivers seem similar, this keep dynamic balance cohesive.

All in all, the use of 3 dynamic driver permit a dynamic articulation without muddiness that would be impossible with all single DD iem apart perhaps Final Audio A8000.



Let's say that the 3DT follow the opposite musical balance than Serial by focusing more on instrument texture presence and definition than their body and note weight. The result is brighter tonality with less boosted bass and more upper mids and pina gain boost. The resolution is sharper, texture is more detailed but the sub bass is more roll off too, timbre is thinner dryer and overall presentation less wide open and more about center stage compression.
Serial is bassier, warmer, lusher and more natural, it's smoother less prompt to sibilance and timbral imbalance too.I did praise the bass of 3DT, but its very different, its cleaner and better separated, mid bass is faster and kick drum better reconstitute yet bass line are harder to follow, less vibrant and bodied and more about beginning of attack for acoustic bass as an example, you will hear better the slapping texture and articulation yet not the extension of it which will get fastly low in amplitude while with Serial it will open in lush resonance, for rumble lover the Serial is notably more enjoyable, sens of weight and dynamic in whole spectrum is better too.
Mids are less recessed with the Serial, apart upper mids which are more forwarded with the 3DT. Vocal sound less wide open and well layered with 3DT, timbre isn't very appealing and in fact you tend to get distracted by the very generous amount of details. Piano presence is better carved in definition, texture of note is richer yet the weight is lacking and sometime higher pitch go trebly, so, higher note will feel more dynamic while lower mids and mids note more distant, making the listen a bit uneven even if strangely captivating.
Treble is very different, way brighter, more brilliant and generous in micro details, more snappy and perhaps faster, more extended too but to the cost of a more V shape imbalance too where percussion will tend to stole the show of every other instrument in jazz track for example, as well, 3DT extract more background noise artifact and texture grain that perhaps aren't beneficial for musicality. Nonetheless, who know what will happen if we exchange this very treble DD with the darker one of Serial, perhaps a miracle! I love 3DT treble but don't find it well balance enough due to mid range recession.
Spatiality is wider and taller with the Serial, just a hint deeper and cleaner with the 3DT, yet, even if space between instrument isn't the cleanest with Serial its wider to. 3DT feel a bit compressed and intimate in stage, lacking in stereo openness, your a bit stock in ''tunnel vision'' which doesn't create long term laid back immersivity like the Serial.

All in all, those 2 are great but very different in tonal balance, dynamic heft and timbre. I think it wort having both even if their no doubt i prefer Serial for its lusher fuller musicality and notably more appealing vocal. 3DT are for those allergic to warm, dark or bassy soundsignature and in that sens, they are great. Technically speaking, 3DT is a notch superior, both in attack speed and resolution, yet tonal balance it's his achiles heel.

VS KINERA URD (2DD+1BA+dual EST-650$)

The URD are more than 2 times pricier and don't feel like so apart perhaps treble part covered by EST driver which is faster and more snappy-sparkly. Tonal balance is a bit different, though a bit dark too it's more U shape and mid range is notably less dynamic, hint more recessed and thinner. Bass doesn't have the chunky slam of Serial, nor the layering, kick drum is even more dark and lean sounding but sub bass line are cleaner.
In term of dynamic heft, the Serial feel more W shape and energic, offer heavier note weight and thicker fuller more forwards male and female vocal.
Timbre is richer too than URD which have liquid one. Everything sound a bit hall like and distant with the URD compared to more in your face presentation of Serial, this tend to offer slightly cleaner and crisper imaging, but the mids are less immersive.
Highs are darker in mid treble region, so its even more soften in texture and bite, making electric guitar more recessed, less bodied too, but permitting higher transparency which will benefit strings quartet for ex. Serial sound less sharp and brilliant for instrument like clavichord, and add more low harmonic body to acoustic guitar, which will sound thinner yet more airy, delicate and sparkly with the URD. You know when I say the Serial need an extra EST to become TOTL IEM, well, its exactly to add this sens of air and top openness that the URD offer, i can say the URD would need the treble DD of Serial to become end game IEM too.
Spatiality is more open and deep with the URD, but the layering of mid range is lacking, so here we have big tall stereo wideness with scooped center stage will center stage seem super stretched with the Serial.

All in all, while both these IEM are darkish, bassy and smooth sounding with wide spatiality, the URD sound less natural and cohesive between its driver, overly soften in texture and thinner in timbre. Apart the EST treble, they aren't superior technically and tonal balance is fuller, less U shape and more natural with the Serial, so it's an evident win i feel, at least in term of sound value.


Ok, now its the fight that will tell if we can get any advantage with multi-DD IEM against a very capable single DD. The SM2 are perhaps the best technical performance out of a DD you can get under 300$, but the tonality is near polar opposite of the warmer Serial, while Serial flirt a bit with (punchier fuller) Harman Target, the SM2 goes DF neutral its own way. SM2 is brighter with way louder pina gain and treble emphasis, bass is lighter and more rolled off in sub bass, their no proper chunkyness or rumble to it but its more textured, faster and better define in resolution, yet its not as well layered and fully restitude in body. Mids are notably thinner, more distant and artificial sounding, male vocal are notably less bodied while female vocal more agressive and less well rounded, less wide and again well layered in dynamic presence too. Yet, SM2 resolution is notch higher even if it can feel forced while its more laid back, warm and dense with Serial. Vocal and instrument tone is more natural, while presence have boosted textured and edge with SM2. When it come to treble, it follow similar path, its sharper and more agressive and analytical with SM2, it seem to extend more too since we have more air, brilliance and sparkle, but mid treble lack the Serial fullness and some instrument and percussions will feel bodyless with the SM2, nonethless their no doubt Serial is Darker and less generous in details retrieval.
Spatiality is so different here, while the SM2 seem more open and airy, it feel scooped in center stage, where the Serial stretch it wide and fowards. So, Serila is wider and taller yet not as deep, but it feel like well, have 3 speakers instead of just stereo separation.
The imaging is notably more articulate in layering with the Serial, while positioning accuracy will go to SM2 for static instrument since its crisper and cleaner sounding.

All in all, SM2 is more clinical sounding but sharper in resolution and faster in attack, yet tonality is fuller, thicker and lusher with Serial and way more musical and natural, bass and mids are more bodied and fowards and layering have more dimension to it making it a more versatile and immersive sounding IEM. With SM2, i listen music with my brain while with the Serial, it's with my soul.


I think it's evident I have quite a big love affair going on with the Penon Serial, and while they could benefit from extra treble extension, i'm far from thinking it's a deal breaker.

The fact that Serial offer a lush cohesive musicality with 3 dynamic drivers is a tour de force by it's own, these are perhaps a dream come true for bass and mid range lover that seek for an all-arounder that is safe for long listening, yet heavy in dynamic articulation.

I own about 200 earphones, and none of them offer this sens of holographic layering where the bass player is fully extract or vocalist widely open and enveloping. Sure, i can nit pick that instrument separation isn't ultra clean or micro details feel recessed, but at they end, we are charm by musicality and the Serial know how to sign with colorful passion.

Add to this the beautiful design, and very generous accessories, and it's an easy recommendation for 300$. Now, I have the UM 3DT for bright side of tonality and Penon Serial for the warm side that isn't lacking in richness, for supreme all arounder, i would suggest the Serial without a single doubt unless your are a treble head.

Highly recommended for bass player or lover, male female vocal fans, those who seek holographic layering that single DD can't achieve, those who appreciate natural dense timbre and those who listen to wide range of music like me from classical to jazz to electronic to soul to.…

Penon isn't amateur tuner and their long experience in audio world is beautifuly showed with the Serial. Again, Bravo!

PS: I wanna thanks Penon Audio for sending me this IEM after i manifest my intense curiosity about them. Their no $ incentive nor official affiliation to write a positive review. Penon will see this review once published. As always, i'm 100% unbiased and subjective in my sound impressions and appreciation.

You can order the Penon Serial here for 299$ (non-affiliated link):https://penonaudio.com/penon-serial.html

You can join their Facebook groups too, for diversify reviews of their products here:https://www.facebook.com/groups/1221974387914138
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Thanks for the review. The UNIQUE MELODY 3DT also looks interesting. I wonder if you'll make a review for them. :)
Very good review. Completely agree 😎👍


Headphoneus Supremus
Penon Strikes Again
Pros: Amalgamation of three separate DD technologies
Incredibly balanced with a complete and correct frequency response
Includes “golden-boy” 0.72mm 2 pin/8 core Penon CS819 full-featured cable, a $49.00 value
Responds to OS133 Cable Adapter (a $29.00 extra, not included)
6mm Pu Dynamic Diaphragm for the highs
8mm Titanium Plated Dynamic Diaphragm for the midrange
10mm Biological Dynamic Diaphragm for the bass
Each handmade SERIAL faceplate is one-of-a-kind
Medium-large size, lightweight
Great soundstage
Airy yet smooth trebles, introducing a non-fatiguing big-playback
Sub-bass emphasis, instead of middle and upper bass
A natural (zero BA timbre) response due to zero BAs used
(Amazingly) perfect, perfect timbre
Fun-fast pace due to neutral lower midrange character
Cable both copper with a splash of silver to dial in the sound
Triple-band crossover network
Three separate sound tubes coming together under a single stainless nozzle
Accurate bass emphasis
Diffuse Harman with a subtle V
Slightly dry midrange character, yet clean like a fresh-pressed shirt
Mid-treble focus, with emphasis in the mid-treble most of all in comparison to the upper treble
Cons: While not basshead levels of bass, satisfying with full-on impact
Ultimately the Penon House Sound, known for full-midrange-action
Better at female vocals than male vocals
Midrange slightly dry, still you bask in incredible clarity and pace, none the less!

I did something a little different than with most reviews. I used the Penon SERIAL for a few days then I searched about what others thought of it. And guess what I found? Everyone is basically saying exactly the same thing about the SERIAL. Do you know how rare that is? Meaning most of the time we have personal interpretations of IEMs. This takes place because people often hear IEMs slightly different. But what’s wild is the interpretation of the SERIAL is exactly the same by every reviewer, including myself. I’m not taking about if the Serial is good or bad, more simply describing the attributes and tonal qualities, yep......they are parallel everywhere I look. So? I guess that simply means everyone is correct....really a first in the audiophile community, as normally there is at least one stick in the mud who somehow has to perceive things differently, then go on to explain why. Not here. But also the other feature that’s normally found across the board is how natural the SERIAL sounds. Truly I needed a review like this one. No fires to put out, nothing to really figure out, no one to fight with. It was all very relaxing like a warm bath, with the lights off. Yep, we need that at times.......to come one to one with the music. To find ourselves again inside the song. A song for the soul. Such accessibly is found with the Penon SERIAL. Why? Well to start 3 Dynamic Drivers. When you hear them in union you wonder why everyone is not simply using 3 dynamic drivers? In a nut-shell the SERIAL is complete and not strange at all, in fact it’s the very opposite of different, even though it’s make up is quite revolutionary. Normally you think experimental means effort, effort to get what’s going on. Nope.......here the sound is smooth and complete, yet with just enough excitement to make it all fun. I’m getting ahead of myself here. Who are Penon Audio and why does the SERIAL IEM exist in the first place?
  1. Penon History
  2. Construction
  3. Sound
  4. Build Quality
  5. Conclusion

Let’s get started………..

Penon Audio and Penon Audio History:

Penon is probably more like a craft beer maker than a big conglomerate manufacture like Budweiser? While both avenues are a route to your IEM destination, big manufactures mass produce printed metal shells like copies of copies of copies. Where Penon is more of a music enthusiast brand making IEMs which reproduce music with a noticeable character and stance. I mean for starters, look at the SERIAL IEM, just look at the colors and handy-work. Could such a shell design be mass produced in a factory? In fact the one-of-a-kind-ness is worn on the shirtsleeve of the SERIAL. No two are exactly the same……….they sound identical due to the focus on interior craftsmanship, but each SERIAL has different designs of impregnated stabilized wood. I tell myself I don’t care about such little extras, then I witness the SERIAL in real-life. What? What is this…….there is an aspect of craftsmanship which you can’t argue with……..when you see the attention to detail and feel the emotion that went into the construction……..it has you stop for a moment. Nothing more than color-impregnated stabilized wood, handicraft. Yet somehow it’s more……more than you would guess from the pictures……because pictures are just pictures……they can’t start to explain the vibrancy of the pieces in real life………but more than that…….the exquisite detail that takes place inside of each colored piece. There is about 8 different individual pieces of color…......but more than that, because they are wood, there is another level of detail with-in each pattern of wood. Each individual piece of wood is a painting unto itself…….and the way they are placed together is another signpost that it’s a product of human expression. These IEMs have soul, both in sound and construction. I’m getting ahead of myself again……..yet this IS a way of describing the Penon Company. Penon doesn’t just make IEMs. Besides the Penon brand, they are a retail house that currently represents/sells 120 different audio brands. Not only a retailer but a renowned cable builder, making 44 different cables/adaptors right now. Penon also currently manufactures 9 separate earphones as of late. With a history going back to 2013, Penon is the logical result of years in the business. With a Penon product there is no middle-man……as this is a factory direct purchase. Penon are simply more grassroots in demeanor. Such focus of intent expands even to their whole IEM line. Where some big companies make all styles of sound signatures, Penon on the other hand continues offering a subtle variation of the same tune. Such differences may be indicative of driver methodology creating creative differences in sound? Still Penon is always driving in a singular direction it seems. There is no room to make an odd-ball tune or throw stuff against the wall and let the buyer be the experimenter. Here we are gifted with another reiteration of the Penon House Sound. While I only own the Globe, the VORTEX and the SERIAL, each is related, offering only a subtle (tune) departure, having more in common with each other than contrasts. While Penon has only made two full-range single driver IEMs, the Fan and the VORTEX, they fully understand the positives and negatives encountered by trying to make a single driver float the boat. So….they are experimenting yes, except this sound is accessible and familiar in the most pleasant of ways.


Sound construction and artistic endeavors:

When it gets down to it, using three DDs is rather unusual. Each driver is responsible for a specific frequency band, in charge of getting that frequency band to the driver is a solid-state crossover system.

6mm Pu Dynamic Diaphragm for the highs
8mm Titanium Plated Dynamic Diaphragm for the midrange

10mm Biological Dynamic Diaphragm for the bass

The big deal here is that that underneath the stainless steel nozzle there are three separate sound tubes. Such a design is imperative to avoid any phase cancelation or frequency interference cancelations! The hand-crafted resin shells are semitransparent allowing slight visibility of each of the 3 DD drivers! The opacity of the top faceplate shows a particular design with the stabilized wood sections reaching over the corners to add to the design. A fairly large vent area can be noted having a red ring for the right and a blue ring for the left. Such an IEM structure excels at being incredibly smooth and soft feeling in-ear. But beyond that the SERIAL shows its been meticulously finished offering a medium-ish semi-custom size. Combined with the stainless nozzle, results in exemplary feel and fitment. Seriously, this has been one of the best fitting IEMs in recent memory. You actually long to have these in your ears. The 0.78mm 2 pin connector remains totally flush to the sides, offering up a style of simple elegance, as there is only front names on the IEM. Yet, those names are totally understated in look, offering further the artistic statement present. Such a grouping of stabilized wood panels on the surface and medical grade resin combine to truly make a pure statement. The choices of wood color are almost like a bouquet of flowers with each color both individual yet contrasting with the color next door. Strangely simple, yet effective in design, the SERIAL could even be one you keep on looks alone.

IEM color has tremendous influence into how we perceive sound. All of us would like to think we are totally objective in perception and are able to hear-through any style of construction “paint-job”. When in fact red cars seem to go faster than black ones? Wedding dresses are totally dependent on color for success……..what about how you act wearing a black suit in comparison to a white sports coat? Color really means something as to how we perceive life. And while the SERIAL is slightly warm, it’s the perfect balance of not boring vividness and smoothness, though it makes you wonder how it would be interpreted if constructed all in black?



First off lets talk about the included cable. This section finds itself under the Sound descriptions as we are going to find out just how great the included cable works, as well as get creative with cable rolling. The included CS819 cable is a looker. Maybe not to your average Joe on the street, but if your of the audiophile persuasion, such CS819 build details and accentuations talk back! Even before the power is tuned on (and just like color) we start to get a clue we got what we paid for. A newer revamped edition goes all out to redesign the chin-slider into a more fluid design, less chunky and more out-of-the-way.........especially if you don’t use the thing! Carbon fiber is scattered about, further enhancing the possibility of better sound. :)

With 1/2 the cores silver plated OCC copper and the other half simple OCC copper we are met with a luxuriously flexible affair. An 8 core hybrid cable consisting of 8 cores and 8 shares a core, it can be ended with any plug of choice be it 4.4mm, 3.5mm or 2.5mm. Still this single cable shows two areas of branding, both on the plug and the cable spitter. A band of color goes to designate the right or left 2 pin. And finally both the two pin areas and the plug area show attention to detail with clear strain relief sections.


Penon CS819 OCC & Silver-plated Mixed Braided HiFi Audiophile IEMs Cable

OCC & silver-plated Mixed Braided IEM cable
8 shares, single share is 19 cores, a total of 8 × 19
Silver carbon fiber alloy splitter, CNC integrated alloy slider
The solder joints is silver–contained tin
Copper Gold-plated plug

Cable length: 1.2M

So how does it sound?

With Penon being a cable builder they could have really matched the SERIAL with anything. Still at $49.00 by itself, the CS819 provides the goods. First off lets talk about sonic balance and what has a possibility of going wrong. When dealing with warmish sound signatures, everything has its place in the equation. Meaning the ear-tips, the DAP and the cable of choice. In contrast (pure copper) 4 wire litz OCC construction can actually sound great right off, but there is a phenomenon at work here. Like any trouble to be found it sneaks-up slowly and unexpectedly. With pure OCC we run the risk of the Penon SERIAL getting slightly boring. Meaning this is not an instantaneous thing…………but happens after a night of listening, to the effect of simply wanting a little more. More in the form of brightness and that sonic excitement that occurs when we add a slight bit of treble to the mix. So price in a way is inconsequential, we are examining cable character here. Again we are looking for balance in that the full-frequency spectrum is represented, but also that each tone is inherently correct and doing its job to make the whole balanced. So moving over to a more mid centric DAP, the litz OCC still starts to show its lack of luster after a while. Going to the included CS819 offers an improvement in the form of added brightness, but beyond that, the brightness is repositioned into a slight soundstage expansion. Such discoveries prove the Penon engineers were thinking when they chose the Penon CS819 cable add. With that comes an ever so slight repositioning of sonic elements, a polishing and shining if you will. The CS819 helped add just a smidge of added clarity and is well worth the price asked, as it’s free with the SERIAL.....in a way? Probably the most important thing we can get is clarity of elements in wanted places, it is a quest of looking for texture in the violins and vocal expressions…..and sure enough we can partake of such adjustments. But of course curiosity creeps-in as curiosity always does…….to try more cables in fact. But before I do, I want to reiterate with-out going overboard, that the CS819 is probably all someone is going to need with the task of basic listening.

Still there is this?

This can be used in addition to the included CS819 cable to change the sound slightly. Believe me, this is one of the most questionable adds I have reviewed. Before I started I was pretty much 100% sure it wouldn’t do anything. But remember everything in the signal chain has an effect.

Penon OS133 Audio Adapter Cable for Earbud/IEM/DAP/AMP


OFC silver-plated cable
Black nylon sheath
4 shares , single share is 133 cores , a total of 532 cores.
Gold-plated copper + carbon fiber plug accessories
Cable length: cable is about 8cm,total length is about 15cm (include plug)

Available type:
3.5mm Audio Male to 3.5mm Audio Female
3.5mm Audio Male to 2 5mm Balanced Female
3.5mm Audio Male to 4 4mm Balanced Female
2.5mm Balanced Male to 2.5mm Balanced Female
2.5mm Balanced Male to 4.4mm Balanced Female
4.4mm Balanced Male to 2.5mm Balanced Female
4.4mm Balanced Male to 4.4mm Balanced Female
3.5mm Audio Male to 3.5mm Audio Male
2.5mm Balanced Male to 2.5mm Balanced Male
4.4mm Balanced Male to 4.4mm Balanced Male

The outcome was that it changed the signal, except it was slightly darker and had more authority. I’m maybe not going to say that everyone should drop what ever they are doing and go buy one! But truthfully it was interesting and cool. The notes were heavier and meatier…….denser and slightly darker. The biggest surprise was that I didn’t think it would make a noticeable difference, yet it did. Now am I going to use it all the time? Probably when extra note weight is needed and that level of darkness, well not exactly darkness…….lets say it added a color, a faint color, and that color seemed a shade darker as a result? Again though its an example of everything in the signal chain as having an affect. I can’t wait to try it with a super bright cable, as my guess is the end results may even be more dramatic? So this ends the testing of the OS133 cable adapter and CS819 cable. For complete transparency here I used the Sony WM1A with MrWalkman’s Firmware in addition to the Penion SERIAL IEM when doing this single test.


This is the brightest cable in our series of tests.

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ISN Audio SC4 4 Shares 12 Cores Pure Silver & Single Crystal Copper Mixed HiFi Audiophile IEM cable

At $99.90 this is the singular most expensive cable used besides Han Sound Audio ZENTOO 4-wire OCC litz copper cable.

While the effects of this cable have been legendary here at Redcarmoose Labs, it became a kind of fix-all for many IEMs, lending an energy and shimmer to the music, affecting everything it touched (almost) positively. Obviously such a cable rabbit-hole is confusing and bewildering at times. As in truth, the ISN CS4 often is not the right choice for IEMs that are borderline bright. So we have a spectrum of playback with different IEMs, and probably each is its own story. But the ISN CS4 and the SERIAL was very much a departure from stock. Details like whispers and vocal accents were showcased, yet maybe not needed. Meaning we are so far from a stock sound that it may take a while before I can accept this playback as totally correct. Meaning we are with-in bounds of pleasurable playback, I’m just not sure if my preferences go to this side of town. Remember it’s the soul of the SERIAL that resides in a style of warmth and while that warmth is still here, I’m not sure I want to trade (any of) it off? Though the soundstage with the added midrange emphasis is spectacular! Adding the OS133 was maybe the ticket, as now I had that soundstage yet stuff was dialed down just a tad. I can tell I’m on the threshold of audio confusion………..though these are my thoughts? In all honesty though this really sounds the best? A $99.90 cable plus $29.00 adapter…lol….more expensive somehow always (usually) sounds better. But I don’t know if this is placebo or what, but this one of the best so far?

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Penon OS133 OFC Silver-plated HiFi Audiophile IEMs Cable

OFC silver-plated cable

Black nylon cover
2 shares , single share is 133 cores , a total of 266 cores.
Gold-plated copper + carbon fiber plug accessories
MMCX connector
2Pin 0.78mm connector (positive and negative concave grooves facing outward)
QDC connector (positive and negative L, R characters facing outward)
Length: 1.2m

Plug: gold-plated

Finally we end up with the Penon OS133 cable. Really this is the inspiration for the OS133 Adapter.

4 shares , single share is 133 cores , a total of 532 cores.

So you have twice the cable (in-action) using the adapter. But other than that it’s the same, except for the 2X plugs when utilizing the adapter. Where the greatest contrasts happened with the thiner midrange and increased imaging/spacial properties of the ISN CS4. Where truly it would take awhile to take that response to heart, adding the OS133 adapter was a match made in heaven……..instantly! Also going back and forth between cables was truly a pleasure being the SERIAL 2pins are flush and welcomed any fast cable change. So……in ending this cable roll test, the included cable showed to be fantastic and better than the Han Sound Audio ZENTOO 4-wire OCC litz copper cable at $249.00 due to the SERIAL not needing the darker response. The included cable was better than the OS133 aftermarket cable too. Though the differences were very close, after a number of back-and-fourths the included cable really started to shine, with added separation and realism.

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Definition of Serial:
adjective: serial
  1. 1.
    consisting of, forming part of, or taking place in a series
So you can see the word means a series. A series of what? Maybe a series of dynamic drivers? Could the name of the SERIAL mean this?

6mm Pu Dynamic Diaphragm for the highs
8mm Titanium Plated Dynamic Diaphragm for the midrange

10mm Biological Dynamic Diaphragm for the bass


After about 4 days of burn-in I was itching to start this sound review…..but I had a word of caution interjected. Dsnuts PMed me and let me know about new discoveries to be made with prolonged burn-in. He said the SERIAL really demands a full 168 hours of burn in! I normally do burn-in though not always quite that much, as I actually have quite a number of IEMs to review, and less burn in would save time. But you know what? Dsnuts was absolutely right, at about 5 days I noted a smoothness never before seen, a cohesiveness which surfaced anew. I shook my head, this again was enlightening as truly the SERIAL was a slightly different IEM, soundstage even seemed wider, and in the end I had new respect for the completeness offered. Finally 7 days came around and yes, the SERIAL was gifted by another level of togetherness, a smoothness which went a-top of the initial ideas of smoothness. Here is a perfect example of you don’t know till you know. Meaning out-of-the-box there was nothing particularly wrong with the SERIAL, it’s just there was more driver separation and less blending of frequencies, there was a great smoothness right off, but burn-in added a quality of “oneness” along with added smoothness. I’m truly grateful for Dsnuts input as there was a big difference between 4 days and 7 days! Way more quality than I could have ever dreamed possible. Though come-on it makes sense, instead of one DD driver, we have three in a series. Go figure?

Besides the smoothness present we are gifted with a style of naturalness which could only take place with the jettison of BAs. There is zero metallic sheen due to no drivers responsible for such an artifact. Don’t get me wrong, my favorite IEMs are hybrids, and I actually have a single 10 BA IEM that’s one of my favorites in response. But BA timbre is a real phenomena. There are actually ways to deal with it, but if we want it to go away entirely simply don’t include BAs. This is such a rare use, of using 3 DDs in a series, that it makes you wonder why it’s not used more? As I like Hybrids and at times.......that BA timbre is very well hidden or placed in a backseat to other sonic qualities noted, yet it’s always there in varying degrees. One of the fastest ways to rid yourself of experiencing BA timbre is to simply switch to a warmer DAP, that or switch to a warmer cable. Luckily we can throw all such nonsense to the wind with the SERIAL. Due to a naturalness provided by the SERIAL we first notice two major elements…..

Accurate reverberations:
Smoothness of character:
Laughingly.......many may guess that my love for multiple drivers employed is to broadcast the sound spectrum well. So to replace those BA hybrid drivers with DDs we would find ourselves in Heaven so to speak? And……absolutely, the $299.00 SERIAL does hold TOTL Flagship qualities, there is really nothing like it in my humble experience. Such are the reverberations that enables me to grab the SERIAL over the top of many other IEMs. It’s that decay that we join our ears with the SERIAL for.......that and balance. The balance part I’ll get to later as it’s a super important part of what makes this IEM a piece of audio art. But there are simply coherent natural fall-off of notes, the way you would guess them to be in real life. Next up is the smoothness, which in reality smoothness means nothing if it isn’t across the board smoothness. As if there was a frequency in a certain place (rearing his head) as the stark standout of anti-smoothness, we could probably say part of the frequency repose was smooth, but this quality is actually connected in a weird way to balance. That’s right, we only truly totally perceive smoothness when it’s a character of the driver in relation to an even frequency response. A BALANCED frequency response in fact! Now you can obviously have a smooth low-end and a choppy midrange and treble……in-fact Hybrids often parlay this style of response, Yet here all is better and more accessible, more digestible…..due to a WORLD-CLASS form of smoothness and balance.

This is the most neutral IEM Penon has ever made. Now don’t take that neutral as not warm, or even not containing bass emphasis. Because this is PENON we are talking about. Such tone is often exploited by other manufactures too. It’s adding room response. Room response helps IEMs emulate speakers in a room due to frequencies bouncing around inside of a speaker cabinet and exiting through the rear and side panels, then bouncing off the side and rear walls of the listening room and changing the FR of the perceived front speaker drivers. This add of lower frequency has been measured and proven to exist in rooms and an add to what is coming from the main front drivers. Such a phenomena takes place in live music playback too, and is partially responsible for live music sounding different than recorded music. The end effect (besides the bass) are synthesizers and choruses sounding slightly distant and containing a cathedral like presence. Combined with the natural reverb and balance and that’s what we have in a nut-shell.

End of review:
HA, I’m not done with you yet. But really that sums up the SERIAL in that you will grab the SERIAL due to a charming way it does reverberations plus the balance. The fun factor, some IEMs actually have the fun left out, but not here................when it all comes together that’s the most important quality. What’s happening here is the Penon tune experts have added room response, but more than that, they tweaked up the forwardness of the midrange which in turn means everything is heard, nothing is actually siting that far back. I have 5 other IEMs yet to review, and more coming today, and tomorrow, but my completeness here is because Penon is complete. Penon Audio have done their due diligence to dial-in this tone, this balance, this magic………that in itself deserves a complete review, not a quick glimpse of what the SERIAL is, but an attempt at describing the full-ride the SERIAL offers every time you put them in your ears.

Here the SERIAL dominates with emphasis on sub-bass and mid-treble. Offering a diffuse Harmon, subtle V shape tuning. Such is the consummate balance, makes you wonder why all IEMs are not tuned this way?


Graphic representation by freelancr

Bass: 10mm biological dynamic diaphragm goodness:
When sub-bass is present in the song the bass comes out to play. While still kept in check, it’s not the most authoritative I’ve heard, but still dramatic and fun. Probably the best quality is how cohesive the over-all sound is, meaning I’ve heard other DD drivers which seem to lay way outside of the stage to become an add-on style of bass. Here we are gifted with the opposite in that the bass becomes the natural extension on the whole signature found like a good dog, loyal and trained. With that said the bass is not speedy nor slow, but on the slower side of the fence from some IEMs. Is this an issue? Not at all due to the balance at hand……the focus is not necessarily on the bass alone, this bass imaging is not exactly super fast nor super delineated, yet there is just enough detail to thrill to satisfy. Such is the tune of the SERIAL. A kind of Goldilocks of sorts. If you were wondering which Penon IEM to try first, there is nothing wrong with the SERIAL being that gateway product. In fact, out of everything from PENON I’ve heard (Globe/VORTEX) the SERIAL becomes the most well-rounded and accessible, In my opinion. Again I will say that despite the unorthodox driver configuration, the SERIAL is very much a solid-well-rounded performer. Somehow they have simply put together a generally likable IEM? And just like that loyal dog……the SERIAL is well trained and stays in-line, despite having a character all its own.

I found a huge divergence of treble personality in cable rolls. Now this does nothing to undermine the quality of the included CS819 cable, it’s just that the 6mm Pu Dynamic Diaphragm has the innate ability to wake-up and parley a broader and more involved soundstage filled with finite elements of trebles. Take note, different cables were showcasing the treble abilities....giving you the freedom down the road to invest in a different cable if wanted. Remember though this cable change is really not essential, as the CS819 cable was gifted by Penon who is (first and foremost) a cable builder. Do you really think they would skimp on their baby? No…….this CS819 is well rounded and slightly spicy due to the small amount of silver added making it a hybrid cable. Obviously it depends on your entire set-up what style of tone you get, as the DAP, the cable and ultimately the IEM go together to distinguish the style of output. Definitely not as detailed and refined as my IER-Z1R DD super-tweeter, yet very few are, if any. Though take in account the Sony IER-Z1R isn’t perfect either. With the midrange of the SERIAL becoming more accessible and heard, the shape, fit and price of the SERIAL too, being just that much more accessible.

While the SERIAL enjoys a polite and comprehensive treble that meshes with the midrange seamlessly. It's the treble you always wanted from a single full-range driver set-up, but never got. It’s that faint extra spice where the magic is to be found. Combine that with the hearty bass action and we are drinking from a full-glass. Only you choose the right music for the correct level of intoxication wanted!

What CAN I say? Penon are the midrange masters, only to be met with even more success due to this style of midrange perfection. Now listen, perfection is a big word around these parts……but, how else would I describe it? Tailored and fast due to the tautness of the 8mm Titanium Plated Dynamic Diaphragm! If there was ever any play in the 10mm bass department, none such excursion can be applied to the midrange. In fact that loyal dog we were taking about to describe the bass character has become a robot…………….a robot dog, no less. Lol

While almost uncanny in the accuracy, here the mid-emphasis holds supreme. And even though we have a seamless joining to the bass, the lower mids take a backseat for the full middle-midrange to shine. That titanium driver has less deviation in path, leading to robot (dog) like precision and execution. In real-world use this means female vocals are done better than males, yet guitars shine with perfect timbre. Also the fun scattering of female vocal reverberations which are spread out into the stage, fall into perfect visibility. This relief is why we came, this organic involvement that sways and swings……………….taking us far from home……into the realm of musical enchantment. Yes, of course the SERIAL is all about the mids, even if they get their clarity from a splash of dryness. It’s that dryness that comes about as a needed contrast to the (somewhat) airy highs and bass textures. Still that dryness is maybe the exact reason Penon chose the CS819 cable in the first place, and why you should be warned that that even though a brighter cable will create a wider treble, keeping that dryness at bay is the single key for over-all well-roundedness.


Laughably, you will find the SERIAL does perfectly well with even your older (thinner) favorite songs of youth. While not sounding like a remaster, they will be brought into focus. Somehow adding musicality and offering forgiveness in times of brightness or lack of bass. While at the same time offering a bigness that you paid for from a modern-day IEM with well mastered tracks. Any genre is dialed in, and the SERIAL is so middle of the road with the basics, it brings those attributes to the table, showing just how it does any musical genre spectacularly.

The stage is really mostly right to left with forward and back being stronger than the up and down.

Inside of the imaging are found the slight aspect of those easter-eggs that you have heard before, but not all the time…….better known as DETAIL. It’s this provocative instant realization that placement is totally correct. And within that placement is the natural occurring bounce that propels the track forward.


Build quality:
The SERIAL is slightly medium-big. Straddling the definition of medium and large. Such a shape is actually shorter in distance from faceplate to nozzle (than some) making the SERIAL more chunky than large. The joy here is both the medical resin feeling, and the fact that the stainless steel nozzles hold tips on like no tomorrow. All those instances of having the ear-tips stay in your ears, upon removal of an IEM can be forgotten. Looking inside the pressure release vents we are gifted with screen covers much like a miniature screen door, as the vents are so big with-out the screens, we risk stuff falling inside. The Faceplate is made up of a multitude of color stabilized wood pieces, each idiocentric of the particular unit you’re buying. Each is an individual work of art, delineating such handiwork, as these could never be made by machines. Such work is truly to be experienced first hand, as I could never get a photo to look exactly right? Interestingly enough the entire shell is composed of the same tone of material, meaning shine a micro-spotlight into the shell at night and the pieces of wood are actually floating in the same resin the body is made of. Such detail goes to show the three drivers as well as the three sound tubes joining directly under the nozzle screen. There is no writing except on the faceplate, and even then the black letters are an understatement. Such cleanness of lines goes one-step further as only a single (red or blue) vent is shown with a single in-and-out purpose. All this simplicity goes the extra mile to go with the (abstract) faceplate in generating a one-of-a-kind art-piece feel to your purchase. As no two SERIALS are the same, surprisingly you will feel that much more individual in ownership after you see photographs of other builds. Flat, completely non-recessed 0.78 2 pins are an uncomplicated joy in use. Writing this review I changed the cables upwards of 15 or more times, always to be met with robust satisfaction.

DSC_0005.jpegcable 3.jpeg
DSC_0004.jpegcable 2.jpeg

The CS819 cable:
Really I have talked a lot about this cable prior to this section. But, to sum it up the CS819 is a combination of traits. 1) One of Penion’s best cable values, it’s sold as a stand-alone $49.00 purchase.


Probably my most favorite aspect of the cable (besides sound) is the easy-going feel of it. It lays any way you choose, and never fights for placement or space. The cable could actually be the perfect size, adding the fact that the aluminum plug mount and cable separator/chin cinch are gorgeous. The carbon "look" on each aluminum piece becomes a great feature, but also adding to comfort as you grasp the cylinders in use. The cable is even stripped with red and blue rings at the 2 pin. Why doesn't everyone do that?

The CS819 comes in as a basic 8 core with half the cores silver plated OCC and the other half standard OCC. 19 total shares per core. Such a build will typically shows itself to hold slightly brighter definition when compared to a pure copper cable. Of course as in comparison to more silver cables, the CS819 goes to show its value at keeping the dryness of the SERIAL midrange at bay, yet not offering quite the soundstage of brighter additives, cable wise. Really for most this is all the cable they will need, or course if you have other cables to experiment with, try them! I actually found the SONY WM1Z, the CS819 and the OS133 Adapter Module to be the cat’s meow at slightly lesser than normal volumes! And………whenever I find such listenability, it can go on all day long………long after the review is written and read, long after the hype has died down……….as off into the sunset I can traverse with such a combo.

The BOX opening experience:
I don’t need to list what’s in the box as the picture here is self-explanatory:



Penon did it again. While not reinventing the wheel, they kind-of have. If you know of a similar IEM idea like the SERIAL………..let me know. As here we find a juxtaposition seemingly new and different adds. While 10mm DDs are a dime-a dozen, few are outrageous enough to experiment with the addition of a midrange DD and a treble DD. Yet that resulting sound appears like you’ve heard it your whole life? With added SERAIL detail and added SERIAL pizzazz………..that makes grabbing this unique IEM over others a natural.

While there may be more expensive IEMs and more “Plain-Jane” additions in your collection, the SERIAL simply goes about its day doing what it does, no matter what style of file quality or genre of music you throw its way. While being a little temperamental as to source, it simply could have been me and my hearing? As truly I could take the SERAIL away (on vacation) and keep it alone in its originality. With such a carful balance and demeanor, the SERIAL represents a special value, no matter what kind of listener you are. At $299.00 the SERIAL comes with everything you need to get started down this avenue, you can choose 3.5mm, 2.5mm balanced or a 4.4mm balanced cable. Simply designate the cable style when ordering. You can also add $10.00 extra if you’re into express shipping, so you don’t have to wait for the magic to begin!

The Penon SERIAL IEM and CS819 cable:

$299.00 USD

The OS133 Audio Adapter module (optional):
$29.00 USD


Equipment Used:
Sony WM1Z Walkman DAP MrWalkman Firmware 4.4mm
Sony WM1A Walkman DAP MrWalkman Firmware 4.4mm
Sony TA-ZH1ES DAC/AMP Firmware 1.03
Electra Glide Audio Reference Glide-Reference Standard "Fatboy" Power Cord
Sony Walkman Cradle BCR-NWH10
AudioQuest Carbon USB
UA3 Dongle DAC/Amplifier 4.4mm

I want to thank Penon Audio for the love and the Penon Audio SERIAL IEM review sample.
These are one persons ideas and concepts, your results may vary.
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Now I will wait for your analysis of the vortex, and the comparison of these two (serial and vortex), as I have small ears, I need to be careful with my choice, to at least try to choose an iem that will not really harm my hearing channel (already i had a lot of ear problems because of iems, i already had timeless and it was screaming in some tracks and also the comfort was not good, it hurt my ears a lot), thank you very much for the review, I'm looking forward to the next vortex!
Wes S
Wes S
Wow, what a great review man! I owned these amazing iems briefly before I decided to focus solely on my full-sized system, and they really are fantastic iems that punch way above their price.


Headphoneus Supremus
Very Engaging and highly satisfying
Pros: Excellent texture, fantastic layered bass, some of the most melodious and smooth vocals.
Cons: It trades musicality for details, doesn't have the best treble region.

From being one of the prolific online seller in the world to a cable then IEM brand, Penon has ventured deep into the Audiophile market. They have been making good amount of IEMs for various type of consumers. They have single DD to multi BA and multi hybrid IEMs under their belt and the Penon Serial is their latest addition. It's an unique kind of IEM with 3 dynamic drivers in a 3 way crossover. The tech is not exactly new in the market but the implementation of the UM 3DT wasn't exactly excellent. Penon has a different strategy here. They have a 10mm bio DD for bass, 8mm titanium plated driver for mids and 6mm PU DD for highs, interesting combination of drivers I must admit.

Penon has been making excellent sounding IEMs and I am expecting a pleasing experience with the Serial. Priced at $299 it comes in only black color and goes head-on against the CFA Satsuma, UM3DT and many other DD based IEMs.

Get one from here:




Serial ships with the usual Penon style box and has 6 pair of tips.



Serial has a unique kind of shell. The body is mostly made out of resin for better stability and durability but the back plate has pieces of stabilized wood on it with layers of resin on it. As usual the shell the solid to the hand and feels light weight. There is a single vent on the side of the shell. The metal nozzle looks good but isn't really premium feeling. What's odd is that even with a resin body the IEM doesn't have a more ergonomically designed wing. This should have been better but thanks to light weight and deeper insertion serial is fairly comfortable.




Penon Serial ships with an 8 core OCC + SPC cable. Its Not the most premium cable in the market but it still looks good and somewhat compliments the IEM aesthetically. A silver coated cable could have made this pairing more appealing. It's an supple and soft cable without much memory problem. It barely has any microphonics to worry about. What I really like is the lack of cable guides. There are some stress relieving at the jack end but doesn't have much protection anywhere else. The cable splitter looks nice while chin slider is a bit too big. Sound wise this cable is not bad, upgrading to something like Effect Audio Grandioso or similarly priced Silver cable will make sense, or else it does the job.



Serial just like any other DD based IEM doesn't really care a lot about the source but it enjoy power without any guilt. The worst performance is with mobile devices but that too is above average while driving it from something like Fiio KA3 and Qudelix 5k brings out the best of it with better details and transparency.


It has 3 DD in a 3 way cross which delivers one of the most cohesive sound in any price range. Cohesive has been a great USP for Penon. Their ORB too was excellent in this regard. This takes it even further. It has a reasonably balanced sound with a Slightly W shaped feel. The mid range is not drowned while the lower end and lower treble region are a bit more forward.

There is little to no coloration while having one of the most uniform notes presentation. I love this. No note feels out of place or gives an odd vibe.

I am using Tri-TK2 and stock tips for this review while changing cables.



Serial is very pleasant sounding IEM with exceptional lower end abilities. I can write the conclusion here. You read it right, you can stop reading here and grab the Serial for it's lower end quality. There is no other IEM in the market which can deliver an lower end like this under $500. If you are a bass lover, want to enjoy the goodness of lower end without any guilt, this IEM will do wonders. The sub-bass extension is excellent, very deep, rumbly and has the eargasmic air moving quality. The whole lower end feels meaty and full which gives it the cohesive but this does lack the speed one might look for at times. The layering and definition of notes are exceptionally good in the lower region.

Now the question arises, Is it an IEM for bass heads? Yes and no. Yes because it's layered and defining prowess with weighted notes make it a delight to use but then it doesn't have the area or volume of a bass-head IEM like Satsuma or ISN D10. Serial's lower end has tunnel like feeling while others are flat.


Loved the lower end. But there is more to it. Bass is excellent, so are the vocals and mid range instruments. It's not the most detailed mid range by some margin but the rounded notes with thicker fuller and weighty nature gives it a calming and soothing signature. If an Audiophile who wants details and finishing definition, let me tell you, this might not be for you. It has very good edge definition with excellent texture on both vocals and instruments. Both male and female vocals have some of most pleasing tonality and timber with a throaty feel. Female vocals don't feel unnaturally thick, that's the beauty.

Another remarkable feature is it's reverb. This reverb gives the Serial an captivating quality. It's simply feels hypnotizing at times. It simply submersive.

Instruments have good details but the resolution and level of transparency is not high. Upper mids have good energy and details but the instruments before and after the vocals can be slightly mushy.


What? Are you still here? Are you not convinced? This is the IEM for you!! Go get it.

If you still are reading on, either you are just curious or like to do some critical listening at times, if you do, this IEM might not be for you. The treble region is not bad, it has good extension and reasonable relevance but doesn't have a lively feeling to it. The spark isn't good. It's doesn't have any offensive feel to it, which is a positive. Layering and separation are not class leading. Micro details are not exactly present in the treble region.. This has two conclusions. 1. It's a bass lover's delight, let's you enjoy without interruption. 2. It's not for those looking for treble details.


Serial has good stage expansion, it's not very big though. Stage height is good near the head but gets better at the upper mid lower treble region which are placed out of the head. The Z-Axis is very good for the price but the X-axis could have been better.

Nearly 80% of the lower end notes are placed inside the head. Vocals have reasonable presence out of the head while 95% treble notes are placed out of the head. Cue placing abilities of this IEM is very good too. It's dynamically adjusting stage gives it very good sonicality.



Hmm, waited for the conclusion? Aight, let me give it to you in simpler words.

Serial is for a bass lover who wants excellent texture, layered notes, excellent sub-bass with meaty mid bass. It does not unload a huge punch or volume but the experience is satisfying. The slower decay helps a lot too. Serial is suited for enjoying the music, its melodious and calm. If you want a lot of details, attack and traction, you can look at other options like Audiosense T800 and even the Shozy B2 makes more sense.

This is it guys, enjoy!!


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Made in China?
Great analyses, succinct and insightful. Listening to them now off my desktop and they sounds great.
Great review 😎


1000+ Head-Fier
Evolution of Musicality
Pros: Significantly matured take on Penon's house sound, extremely balanced and versatile tuning
Excellent dynamics
Delicious sub-bass with excellent tactility/physicality
Rich lower mids that do not predominate over other frequencies
Ideal upper mids elevation, good energy without any fatigue
Well-balanced treble response that hews closely to neutrality
Excellent soundstage height
Superb layering
Very precise imaging
Very good timbre and coherence
Great fit and comfort
Excellent stock cable
Cons: Resolution doesn't quite match BA/EST implementations
Not the absolute largest soundstage out there
Anti-sibilance scoop mutes some instrumental harmonics
Minor channel matching issues

Introduction: The past few years have seen a renaissance in dynamic-driver based IEMs, and a few of the more adventurous manufacturers have begun to branch out into triple-dynamic earphones (a category which historically has been represented by only a few implementations, most of which shall we say left a fair bit to be desired). I really the Unique Melody 3DT last year and it remains one of my favorite IEMs, although the upper mids and lower treble are tuned a bit aggressively on that model. So I was extremely excited when I heard that Penon Audio was developing their own triple dynamic, especially since Penon is one of the few manufacturers which reliably employ a more restrained and neutral (to my ear) pinna gain than is often the case with ChiFi earphones.

Due to life circumstances I was taking a break from the hobby when the Penon Serial was finally released, but although I am late to the party I can nevertheless now affirm that the Serial does not in any way disappoint, and is one of the most compelling options out there for those who love the sound of dynamic drivers but are hungering for more technical capability than most single dynamics can provide.

I would like to thank Penon Audio for providing me with a sample of the Serial in exchange for my honest review. You can purchase a copy for yourself here at an MSRP of $299.

The specifications are as follows:
  • Driver: 3 Dynamic Drivers
  • Impedance: 18 ohm
  • Sensitivity: 103dB
  • Frequency response: 20-20kHz
  • Connector: 2Pin 0.78mm
  • Cable: 8 shares OCC & silver-plated Mixed Braided

Packaging & Accessories: The packaging comes to us in the now-familiar Penon Audio classic yellow slip-cover — a bit spartan, not exactly signifying the outstanding audio quality found within, but of course perfectly serviceable. Within the cardboard box itself is a blue faux-leather zippered carry case — similar to that which for example graced the Globe, although it seems to me that the quality has been improved (for example, the dye seems richer this time). There is also a leather pouch for storing the included Penon CS819 cable, which is a nice touch — especially for those given to cable rolling.


The CS819 cable (a mixed OCC and silver-plated braid) is itself quite good as an aftermarket cable, and the inclusion of a $49 cable with a $299 IEM is certainly to be commended. The other accessories are quite satisfactory as well — the normal blue and green sets of silicone tips (as usual, I prefer the green) often included with Penon IEMs, as well as a set of foam tips, a cleaning brush, and a cable clip.

Build & Comfort: Coming from the gargantuanly-sized and fairly heavy UM 3DT, I was amazed at the normal size of the shells of the Penon Serial and even more so at their extremely light weight. The resin is shaped in a fairly rounded manner which should work for most ear anatomies, eschewing the semi-custom shape which can be much more hit-or-miss. The faceplates of the Serial follow the now-popular trend of using a stabilized wood panel, multicolored but still fairly restrained in appearance especially being yoked to the black resin shell.


Isolation is very good despite the presence of venting, especially since the shells fill my medium-small ear cavities quite well. I experienced no driver flex or vacuum effect. The shells are quite comfortable even over longer listening sessions, although the protrusion of the shells prevent the Serial from being a good candidate for side-sleeping.


As far as the driver configuration goes, the Serial actually differs a bit from the approach taken by Unique Melody with their 3DT. Whereas the latter employed two 7mm drivers to handle the bass in tandem and a single 10mm driver for the mids and highs, Penon has opted to deploy a 10mm biological driver for the lows, an 8mm titanium driver for the mids, and a 6mm PU driver for the highs. There is a three-way physical crossover to separate the sound frequencies.

I will note that my copy had some slight channel matching issues, nothing horrible, but others have experienced some issues as well so it’s something worth mentioning. However Penon customer service is always excellent at resolving issues should they arise.


Signature: The Serial — like most Penon IEMs — has a signature which is difficult to immediately pigeonhole. What is readily apparent from the first moment, however, is that the Serial is easily the most mature tuning I have heard from Penon yet. It's definitely not neutral, it has the characteristic full-bodied musical midrange of Penon's house sound, but it is no longer so bold and perhaps even ostentatious as on some other models; rather, it is tastefully restrained and extremely well-balanced with the other tonal regions. The bass is somewhat emphasized, although once again in a very tasteful way, and certainly emphasizes quality over quantity. Treble, on the other hand, is fairly neutral aside from a mild-to-moderate anti-sibilance scoop. All in all I think the overall presentation is close to a bass-boosted neutral (although again with a tasteful addition of some of Penon Audio’s signature lower mids warmth), but is quite a bit more dynamic sounding than is typical for this signature.

One thing to note about the Serial is that it is extremely tip-sensitive; I cannot remember the last time I rolled as many tips for an IEM as I did while writing this review. On the one hand this offers probably one of the most customizable sounds out there without involving some sort of tuning mechanism; on the other hand, one can perhaps even get a bit overwhelmed by the number of choices if your tip collection is large!


Bass: The sub-bass here is extremely delicious, with beyond excellent physicality, and the bass is biased somewhat toward this subregion. The mid-bass on the other hand is no slouch by any stretch of the imagination, exhibiting stupendous control and outstanding texture. There is plenty of tightness and agility throughout the entirety low end, enabling the not-insubstantial elevation to nonetheless remain in good balance with the other tonal regions. Being powered by a DD the decay is slightly on the slow side — though only enough to impart a moderate sense of atmosphere to the sonic presentation, and it always maintains good cleanliness. Note weight is somewhat thicker than average, but the notes themselves have a very good definition to them. All in all, it’s been a long time since I was this pleased with an IEM’s bass response.

Mids: The midrange is the bread and butter of the Penon house sound, and although some might consider the Serial to be something of a departure from this house sound, I actually consider it to be an evolution of it instead. The familiar warmth and fullness are still here, yet rather than the euphonic exuberance of previous models, we instead receive an organic bridge between the bass and treble, one which hints enticingly at lushness but always remains tempered by maturity and a sense of faithfulness to the recording’s natural properties.

The lower mids are, to me, the star of the show, and have a wonderful warmth, richness and texture that nevertheless does not predominate over the rest of the tonal regions. Pianos sound absolutely outstanding, with just the right note weight for my preferences. Cellos likewise sound very full and rich, although depending on the mix sometimes they can be just a bit too thick. Male vocals are not as euphonic as on models such as the Globe, opting instead for an extremely natural and tonally correct presentation.

But of course, great lower mids on a Penon IEM are not surprising. What I was pleasantly surprised by, however, was the upper mids which to me have now found their sweet spot, being more prominent than on other Penon models but still well back from the (to my ear) exaggerated and shouty Harman target. Female vocals and strings now have their proper energy and presence, but without any shout or fatigue whatsoever; sibilance, likewise, was nowhere to be found.

Treble: The treble region displays a similar evolution to the Penon house sound: whereas some of their prior models have leaned somewhat dark, here Penon has opted for what is (to my ear) fairly dead-on neutrality. This does come with several caveats, however. The first is that proper burn-in is a necessity, as for many people initial out-of-box experience can be a bit underwhelming in the treble region. The second is that even after burn-in, there does remain an anti-sibilance scoop in the lower treble that somewhat mutes certain instrumental harmonics. It is a much less aggressive scoop than on many other IEMs (the UM 3DT comes to mind here), but it is there and buyers should be aware of it. Although this is probably my favorite Penon IEM for treble that I’ve yet heard, nevertheless it’s still not an IEM for trebleheads. But it does strike an excellent balance in that it retains a respectable amount of air and sparkle while accomplishing the task of staying thoroughly fatigue-free.


Soundstage & Technicalities: Although the Serial is a hybrid, it is still a triple-dynamic hybrid and so one expects the technicalities to improve over a single-DD while still falling somewhat short of BA-level performance. And in general, I think this holds true, especially in resolution and detail which, while respectable, are not earth-shattering. But there are some areas where the Serial manages to exceed these expectations: for example, the soundstage has good width (though certainly it is far from the widest IEM I have ever heard) and it actually has good depth as well, but what is really remarkable is how incredibly tall it is. This advantage in height in turn allows the layering to be close to the best I have yet heard in this price range, even despite the fact that the warmth of the midrange prevents there from being a lot of air between the instruments. Add to this the outstanding and nearly-holographic imaging performance, and the result is a level of technical performance with which I am extremely satisfied. Yes, the timbre and coherence of the Serial do not quite reach the levels of the best implemented single-DDs, yet especially after burn-in (the midrange DD in particular needs some break-in before it gets into good sync with the other drivers) they get fairly close and much closer than almost any traditional hybrid.

Select Comparisons:
vs. Unique Melody 3DT: This is the fairest comparison I can think of, since they are both triple-dynamic earphones selling around the $300 price point. The Serial has noticeably smaller, lighter, and more comfortable shells, and there is no driver flex or vacuum effect unlike the 3DT — although the tradeoff is that the 3DT isolates better. The 3DT has a somewhat colder midrange in general, and it has more aggressive and more peaky upper mids and lower treble — although these do give the 3DT a greater sense of openness, clarity, and perceived resolution. Technicalities in general are close, and so other than fit issues (which are far from insignificant!) the decision comes down ultimately to tuning preferences, with the Serial being more musical and relaxed and the 3DT more energetic and open.

Conclusion: The goal of the triple-dynamic driver setup is clear: to attain to at least a significant measure of the technical capabilities of hybrids, without their inherent compromises in timbre and coherence. I think it is beyond clear that Penon has achieved this goal, and done so at quite an attractive price point. The tuning is, in my opinion, a significant step forward for Penon: it is now much more balanced and extremely versatile, while still retaining the fundamental musical appeal of the Penon house sound. The Serial has my complete recommendation.

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Had these and loved them. Sold them for quick cash and regretted it ever since. Gonna buy them again some day. Great review.
Scuba Devils
Scuba Devils
Great review and I also sold and regret! I will definitely buy again.
Thanks for your time to write this review! really considering buying a set:)!:ksc75smile:


Headphoneus Supremus
Penon Serial. A unique 3 dynamic earphone.
Pros: Utilizing 3 different sizes and types of dynamics with each driver specializing in the sound region it is taxed with. 3 way crossover design in a semi custom all resin shell with vent out back. .78mm 2 pin design. A diffused wide stage with excellent detail, more neutral in tuning with sub bass emphasis. Very good clarity and well balanced. Non fatiguing treble, clean well imaged mids with a proper bass emphasis. Incorporating one of the best value Penon cables the CS819.
Cons: neutral lower mids, male vocals are not the best on the serial.
Penon Serial

Triple dynamics earphones are rare in the industry and even more rare if you think about how many hybrids, dynamics, tribrids and all BA earphones are available vs the triple dynamic. The idea behind using 3 dynamics is to focus each dynamic driver on one aspect of the sound tuning. Penon has taken that idea one step further and incorporated 3 different types and sizes of dynamics with each driver specializing what it does for the sound bands it is taxed with.

The treble dynamic is a smaller more agile 6mm Pu diaphragm dedicated for the highs, 8mm titanium plated dynamic known for its detail and imaging properties for the mids, 10mm bio dynamic specialized for its bass properties. It is encased in an all resin poured housing with a vent out back utilizing a 3 way crossover system finished off in a 2pin .78mm connector design. The size of the housing is a compact medium in physical size for an all resin design, which should fit a majority of ear shapes with comfort giving decent passive isolation.

It has been a while since Penon has done a pure dynamic offering and a first for a triple dynamic design. For fans of dynamic earphones these should catch your interest for several reasons. Firstly this particular design is even more rare as it is using 3 different sizes and 3 types of different dynamics. Could be the first in the industry actually. Then the other aspect is that it is designed and tuned by Penon which if you go off of their history of in ears, you're getting a highly refined high quality product. All their designs and tunings are done in house. Penon does not produce numerous models of inears under the Penon brand, again the only other dynamic earphone offering under the Penon brand was their limited edition Penon Fan earphones.

Standardly disclaimers: I would like to thank Penon audio for the review sample. An early production sample was provided for my take on them. I have no affiliation with Penon and will relay how I hear the Serial to you, the enthusiast. If you must own the serial you can buy you a set here. They have been burned in for a week straight and are now ready for evaluation. Sources used are as follows. IBasso DX300Max, Fiio M15, Shanling M6 pro, M5s, M3s, Fiio K2 2021, KA3, IBasso PB3, IFI Black Label for amping.

What you get.

Serial comes with Penon’s Blue rectangular zip up case. Hearty and roomy this case has been the mainstay of all Penon products. Why change something that works? It has enough room in the case for the Serial, the cable and your tips. 2 sets of silicones, a medium pair of foams, and a very nicely matched Penon CS819 cable in any termination you want when ordering. Highly recommended, balanced termination using a balanced source as the Serial loves a bit of power.

The CS819 is Penons basic 8 core hybrid cable. Half the cores are silver plated OCC and the other half OCC, 8 cores 19 shares per core. The cable pairs very nicely with the serial sound presentation as it is mostly higher end copper in sound properties which adds a bit more body enhancing a natural tonality with a solid bass impact to the Serial sound presentation. The retail value on the CS819 itself is $49 and is worth every bit of that money. These cables are without a doubt one of Penon’s best value cables. Not to mention how good it matches with the Serial. The cables can be purchased here.

While a lot of folks might overlook the included cable with their earphones. I will tell you Penon has improved their included cable pairings. You didn’t get this level of cable with their previous earphone offerings especially at the retail price of the Serial. Let me put it this way. The Globe being sold for the same price has an ok included SPC cable. But the ok cable is not the CS819. The CS819 was included as a sound design aspect for the Serial. The copper element of the cable is a good clue in the types of cables you should try to match up with the Serial if you are the type that never lets good enough alone. Of course using higher end cables on the Serial yields even better sound. Silver based for more detail, more treble and stage expansion. Copper based for more fullness, greater note weight and the best bass performance. Or how about a bit of both. Shown with upgraded Penon Mix

The sound
Serial leans a bit more toward a reference type neutral diffused harmonish tuning. It is a mildly V shaped in signature but very tastefully done to add enough emphasis leaning toward sub bass and the mid trebles. This is the type of tuning what you would hear more commonly for higher end headphones. Given the technology and drivers involved. Why not go for a wide expansive neutralish mild v tuning. Its tonal qualities are more neutral in its mids presentation with a sub bass boost is how I would describe the sound profile. While the Serial is not a ruler flat by the numbers neutral tuning. I doubt Penon will ever do a tuning like that, however the Serial is as close to a neutral tuning as you're going to hear from the group. This is a slight departure from their BA offerings as their BA/hybrid offerings all have some type of mids coloration that is the hallmark of the Penon sound. Rated at 18 ohms with a 103db of sensitivity. The Serial sounds great out of anything, easy to drive but due to the dynamic nature of the design, amping the serial has its advantages for increased dynamic range, expansion and detail. Serial likes a bit of current and power to achieve optimal sound.

Is handled via 6mm pu diaphragm. Micro dynamics have their inherent strengths on the high notes. Just based on my own experience with micro dynamics. Companies like JVC, NuForce, Final and Sony has utilized the micro dynamics to full effect in the past so it was good to see Penon using such a driver. The idea of utilizing a dedicated dynamic treble driver is that it works like a tweeter driver for all the notes past a certain high frequency. What you get is a clean, clear detailed separation of the high notes. Just my opinion but I wish more manufacturers would use dynamics for highs. The advantages of using a dynamic is that you get a more natural tonal and better blended treble character when using a dynamic.

Its emphasis has a good balance of presence and detail. Imaging and transient qualities of the Serial for the treble is very good. As a side note I do recommend a burn in for the Serial as the trebles on open listen was a touch subdued, the treble dynamic seems to wake up and expand with better qualities with burn in. Also as a side effect, expanding the scope of the stage presentation. What's very inherent with the Serial treble is that it blends with the rest of the sound like it was coming from a single driver. Using a 3 crossover technique to achieve that coherency the treble blends a natural smooth non fatiguing take on treble within the sound presentation. True to the Penon house sound, the treble presentation here does not stand on its own, but plays more of a supporting role for the mids and bass. As such you will not have to worry about treble grain or undue treble spikes for a Penon tuned IEM. Treble design has the most emphasis for the mid trebles with a dedicated deemphasis for upper trebles. I wouldn’t say the treble is overly rolled off, it is more deemphasized for the upper trebles to not cause a tonal shift or fatigue, letting the natural mids sound qualities be the star of the show for the Serial sound presentation.

Depending on the tips and cables you use. Trebles become airy and better extended but for the most part its detail level is done very well for the given price level. I own the IER-Z1R which also uses a dynamic for trebles and those are my bar for using dynamics for trebles. And while the Serials treble presentation is not as refined sounding, it's got a satisfactory quality and more importantly blends well with the overall sound presentation. Treble tonal qualities, its emphasis is leaning toward a smoother presentation, agile, crisp with good extension and detail are its strengths. Excellent treble dynamic chosen by Penon.

Mids of the Serial is utilized by a titanium coated 8mm dynamic. Titanium plated dynamics are known for its clarity and detail qualities for the mids. Here we get that with the Serial. The strengths of this particular driver comes through in this design and I would put the mids detail as above average for dynamic earphones. The tuning is a bit of a departure for Penons BA design. This is the area I feel has the most neutrality in emphasis and tonal qualities. Folks looking for a more meatier sounding earphone might be a bit disappointed with what Penon has done for the Serial. The mids are detailed, clean and have about 8 dbs of pinna gain for upper mids presence.

It does female vocals better than male vocals since the lower mids is where there is less emphasis. Its mids are more accurately presented vs being overly exaggerated or having too much of anything. It is more closer to a monitor type neutrality vs being too dimensional or thick in note weight. Its timbre while accurate comes off a touch dry with a quicker sustain. The tightness of the sound is clearly evident from the upper mids to the lower mids. I can tell the titanium dynamic here is a bit stiff and perhaps does not move air as well as the bio dynamic used for the bass. Serials clean imaging, its wide sound presentation along with that detail is the strength of the Serial mids dynamic. As mentioned above female vocal renditions hit them high notes and these are so proper for female vocals.

Instrument separation and imaging is also a stand out for the mids design. The sound presentation is uniquely wide in earphone presentation. Wider than tall or deep. Sound has more depth than height but the width of the stage on the Serail adds to that neutrality reference headphone like presentation. Due to how wide the serial sounds you actually get a better separation in the presentation for instruments that play on that field. Its black space with that wider diffused stage provides a nice broad canvas for you to pick out details. Folks that like to listen to big bands or live performances will love how the serial sounds for such recordings.

A 10mm bio dynamic here is a bass specialist dynamic that was used on previous earphones like Yanyin, Vsonic, and Sony products. The strength of the Bio dynamic is its ability to have a roundness in bass tonality with an ability to dig deep without much struggle. It is the bass dynamic which is the biggest driver being used for the Serail and I have yet to hear a bio dynamic fail at bass. The emphasis for the bass presentation is more sub bass than mid bass. It has a goldilocks of bass emphasis at roughly 8dbs of sub bass shelf. It has the right impact and anything that hits them sub bass notes the Serial will come out to play.

The transition from the mids to the bass end is seamless, smooth in transition and is once again very coherent with the rest of the sound design. Mid bass speed is about average but is fast enough to keep up with busy metal tracks. Beefy enough to sound proper with EDM and bass genres. Its deeply textured sub bass rumble is excellent. These are not basshead in levels but satisfactory for bass to sound complete with a proper sub bass extension and rumble. As a design choice you can have a neutral lower mid emphasis but a neutral bass emphasis? I don’t think so. Never heard a Penon made Iem with neutral bass. I doubt they will ever tune an earphone with neutral bass. Bass is very gifted emitting a high quality bass definition to impact ratio. I have to give credit to Penon in trying out various types of dynamics to achieve better results for its bass presentation and the Bio dynamic has proven to be one of the best for earphone designs. Serial has a proper bass and being true to the Penon sound. You get a satisfactory bass end to enhance your music. The quality bass here is not only a strong suit but the emphasis is perfectly suited for just about all types of music you listen to.

In the end
The Serial is yet another fine example of Penons tuning prowess and their ability to present one outstanding earphone after another. They went for a slightly different tuning using a different unique driver design this time. The Penon fan was a precursor to what the Serial is. These are unique in many ways using 3 different sizes with 3 different types of dynamics all 3 with excellent ability to portray an accurate sound taxed for their sound output. The coverage from the lowest of bass notes to the highest airy treble notes are easily portrayed with the 3 dynamics throwing out their absolute ability. I have posted on previous Penon earphone reviews that I have yet to see Penon do a neutral tuning.

The Serial my friends is the closest it will get to a neutrally tuned Penon earphone it will get from the group but one with some outstanding addictive technical qualities. Their wide earphone stage presentation mimics a headphone reference stage and in doing so the Serial portrays a different type of musicality. True to the Penon house sound, the Serail is all about the mids and its rich bass presentation with a clean smooth detailed treble. Its dynamic sound tuning is every bit as engaging as anything they have made in the past. It is good to see Penon trying out a different variation of their house tuning philosophy and it seems everything they make reaches a certain level of sophistication and ability. The Serial is the most unique out of their line up and is a great addition to the Penon collection. As always, thanks for taking the time to read.

Because you asked. Some comparisons.

Penon has a hybrid that is priced the same as the Serial. Yes we are talking about the Globe.
Vs the Globe. Globe uses a full range Sonion BA for mids and a Knowles BA for trebles + a 10mm dynamic for bass. If there is a classic hybrid that is a fine example of the Penon sound. It is the Globes. You can read some reviews of the Globe here. Against the Serial. These two have similarities in treble and upper mids emphasis but from lower mids to bass is where they are different. The Globes have more lower mids emphasis therefore it has a greater note weight and fullness to its tuning. It is more efficient vs the Serial but volume matched the differences are evident. Dynamic timbre vs BA timbre there is a difference there. Though BA timbre some may look as a negative but if you haven’t heard a Sonion BA do mids proper then you need to get yourself an Orb or Globe and hear a Sonion BA do mids proper. Serial has more of a natural sound signature but has more of a neutral lower mids emphasis so music sounds more accurate and not as forward sounding. Presentations are different. While the Globes have a bit more in the way of bass emphasis and a touch more warmth to its tonality, I have to give the bio dynamic bass of the Serail the edge when it comes to bass. Both are very good bass ends but the Serial bass has a slight edge in detail and quality over the Globes bass. Both have similar treble emphasis with the serial again emitting a touch more naturalness and smoothness for its treble end. I would also give a slight edge in stage expansion to the Serial. Globe however is very close in stage here as well. Both are wide with the Globes having a bit more in the way of height of stage.

Against the ISN SCB2.

You want to talk about stark differences in presentations. The SCB2 is as close to a western tuned IEM made by a Chinese manufacturer as it gets. Its tonality is warm with a bit of darkness to its tone due to the big bold lower mids and mid bass it has in comparison to both the Globe and the Serial. The SCB2 is a much more colored earphone vs the Serial. More in the way of mid bass so for folks that love them some bold forward bass the SCB2 is what that is. It's got a unique tall and deep sound to its presentation and due to the emphasized lower mids and bass end the SCB2 is uniquely suited for bass genres and more weighty music in general and one of the better dynamics for male vocals. Its treble has slightly less emphasis vs its bold bass end but has a proper extension and treble presence for its overall tuning. These are the opposites of the Serial presentation with more of a neutral level of lower mids so you couldn’t get two more completely different presentations than these two. Serial definitely wins the stage here width wise but again that unique tall full sound signature of the SCB2 has its own musical sound that some will like more over the Serials more neutralish presentation. You like your sound bold forward with a rich tone that is what the SCB2 is all about. The Serial does not sound as compact with a wider more diffused sound presentation. Its bio dynamic here is more focused in the sub bass region the SCB2 more mid bass but has enough sub bass grunt to make it sound complete.

So going from the least colored sound tuning to the most
Serial > Globe > SCB2
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@listener26 all 3 you mentioned would be an upgrade to the H40. Try out the Aladdin see how you like that one since it is the cheaper of the 3 earphones.
@Dsnuts thanks bro, my h40 was one of the best I've ever bought and has prevented me from buying anything else for 2 years. I hope i get another good buy from this 3.
Love the review! Could you make a comparison between these and the ISN H50? Not sure which one I should pick. I'm a basshead, but clarity in the mids and highs are also quite important for me since I game quite a lot