The Tourbillon Pro is the latest addition to the Keep Hifi roster, and it is available here (unaffiliated link).

This sample has been provided by KeepHifi, but the opinion is mine alone.

They only asked if I can write a review, and since I like to have a finger on the pulse of the low price segment, here it is.

The IEM features a single 10mm Dual-Magnetic Circuit & Dual-Chamber Dynamic Driver.
The driver itself sports a PU+PEEK+DLC with Blue Diamond Coating Composite Diaphragm. If you are wondering what all the acronyms stand for, worry not, we can decipher that together. PU is polyurethane, a soft polymer that is usually employed for parts of the diaphragm that require ample movements. You guessed it, it is the part that deforms the most and it is responsible for bass. PEEK is a polyether-ether ketone copolymer, a relatively stiff one, making up the dome of the diaphragm. This area needs to remain stiff in order to vibrate very quickly and with high displacement, but with little deformation. In order to further increase the rigidity of this area, a DLC (Diamond-Like-Carbon) coating is applied on top of the PEEK. It’s called Diamond-like it is hard like diamond, but in an amorphous state, unlike diamond, which is crystalline.
View attachment 5_00d2e786-2e31-426f-93d7-1db130610283.jpg.webp
(from KeepHifi)
The point of the dual chamber is to improve the layering and spatial cues (from the website).
They have a Sensitivity of 101dB±3dB/mW@1KHz, Impedance of 19±2Ω @1kHz, Frequency Response: 20-20KHz (according to the manufacturer's website).
They cost around 69-100USD, depending on the offers.

They aren’t the easiest to drive, but no monsters either. Since they come with a stock 3,5mm terminated cable, obviously the volume knob has to be turned quite a bit more compared to the 4,4mm ones, simply because most sources have the 3,5mm output port less powerful than the 4,4mm one.

There is a lot to like about the Tourbillon. The metal shells are beautifully finished in dark metal, they are very shallow, some of the thinnest I have seen so far. The sit well in the ear, thanks to a nozzle that has the right length and angle (for me). They overtake the Meze Alba and the Letshuoer DX1 in this regard, being a lot more comfortable than these two. I can wear the Tourbillon for hours without any issue, no pressure building up, thanks to the two vents, one located right below the nozzle and the second at the base thereof.


The cable is a 4-wire twisted one, with two tones, anthracite and some light grey. One important mention, I find the cable to be integral part of the tuning. I don’t know if this was intentional or just a happy accident, but I find them to sound better with the original cable rather than replacements. The cable is very soft and malleable, with zero microphonics. Overall, one of the nicest cables at this price point. I am a big fan of thin, flexible cables, and I am ready to trade some SQ for comfort, but in this case there was no need, the cable included in the box provides both.

Apart from the cable, KB Ear also included a puck-type carry box, looking like a cheaper version of the Eletech ones, made of leatherette and with a soft touch interior. It is spacious enough for the IEM and the stock cable, with spare room for all the tips, or IEMs+Upgrade cable.
Their sound is dark-neutral with even energy throughout the mids.

Before we dive deeper into the sound, one mention: there is a negligible amount of sound escaping towards outside when listening with them. Not enough to attract any complaints from my family when seating on the sofa next to them while watching TV, but there is some.
I have used a variety of sources, such as the LP W4 dongle, but mostly the Nipo N2. I realize the huge gap between the DAP and the IEM, but at least I was sure there was no shortage of power.

Rather than splitting the sound into bass, mids and treble, I think it is best to let the music do the talking.

I have "decoded" them by comparison with Hidizs Mk10, a 50-60 Eur single DD, Letshuoer DX1, a single DD priced at around 100Eur and Meze Alba 150Eur.

Katatonia – Colossal Shade
Dark atmosphere, with the bass wrapping around your head and creating a cloud into which the rest of the music is played. Bright IEMs do not fare too well here, as they are ruining the amosphere. It is not the case of Tourbillon, which has enough darkness in them. The cymbals are displayed proudly, close to the center, while the voice is intimate (as it should be) and with the usual amount of silent desperation. There is good of clarity in the mids and mid-bass, while the bass drums are rather tactile. In typical DD fashion, the treble is good, with the most natural timbre, but lacking that extra bit of air that is given by the EST drivers. DO not forget though that an equivalent EST set, the ISN EST50 sets you back around 500USD, which is at least 5 times the price of the Tourbillon.
The “breath” of the bass guitar is felt throughout the song and it adds a nice foundation for the rest.
Alba has a fainter but more articulated mid-bass and more energetic treble. But things are not all rosy, there are some traces of sibilance. Now, I am not very sensitive and I can listen without a problem, but if you know yourself overly sensitive, it might be a good idea to steer clear of the beautiful Alba. As soon as you increase the volume, the magic is lost, they sound too cheerful for this depressive music. It’s not that it doesn’t sound good, is just that for darker stuff, Tourbillon is better. Overall though, Alba sounds more accomplished, more detailed and more airy.
Hidizs MK10 is another step in the direction of light. No darkness whatsoever, this comes at the expense of the atmosphere, but brings perfect clarity to the table. It is yet another way to enjoy this music, with nice bouncy bass lines and very energetic treble. Also, the upper mids are elevated, bringing them closer to dangerous territory. Luckily, they stay mostly inside the safe lines.
If I were to choose a favourite, for this song I’d go with the KB Ear, for the atmosphere or either of the other two for details, in particular treble.
However, the imaging of Tourbillon wins hands down.

Iron Maiden – The empire of the clouds
The trick here is that you have a full heavy metal band, with three guitarists, no less, but also strings and piano and even some wind instruments at times. All has to fit in the confined space of an IEM. Is it possible?! KB Ear seems to think that the answer is yes. While Tourbillon does not excel at details, being more relaxed than resolving, it does a wonderful job at maintaining the many layers of Empire... separated, so that when the orchestra kicks in, it does so in an additional pocket of space, one that you almost didn’t know it existed (compared to my modest expectations, that is)
I realize it seems counterintuitive to have less details but better layering, but this is indeed the case.
Mk10 shines with details, in particular in the treble. There is a flurry of cymbals that keep resonating in your head forever. The timbre and the energy of the cymbals is just fantastic. Un fortunately, there is a trade-off between this enhanced treble resolution and layering, as, you see, Mk10 tends to melt together the guitars and the orchestra rendering the layering rather flat.
Alba finds the middle ground, with good clarity and good treble energy. There is maybe a touch less energy than Mk10, but more than Tourbillon Pro. The layering is average, and the strings can be heard, but flattened out to some extent.

Billie Eilish – Billie Bossa Nova
This is a test of female voices, timbre and distance. There are some castanets at the top of the stage, that have to remain audible and textured throughout the song.
Tourbillon manages to keep the voice close to the center, but the sparkle brought in by the castanets is lost to some extent. The L/R separation does not feel that great either. All in all, this song makes them sound more like a dropped treble, bass-head IEM. Upon increasing the volume, the treble picks up some force, but the bass becomes overwhelming.
Both Alba and DX1 have more air at the top, sounding more detailed and with greater vocal clarity.
Mk10 is sounding more rounded up, even though a bit flatter from the point of view of layering and with an intimate stage. As it is often the case in this price range, there is a bit of thinness in the mids, in particular lower mids, but not too serious. The treble is exquisite, my favourite of all this crop of IEMs. In many ways, Mk10 is a Tourbillon with more treble and a bit more presence.

Brandee Younger – Brand New Life
This is...how should I put it?! Too bassy. Depressed as it is, the treble finds its way to my ears and it is delightful. The texture is much better than expected, even though some of the dynamic details are either hidden or simply not present. The harp sounds natural and the voice is pretty forward. The relative lack of air makes Tourbillon less appropriate for this kind of music, though.
Alba has a larger stage and more ethereal upper notes. From the start seem more open and more sparkly, with a soft touch making the notes efortlessly float in the air. The voice carries more texture than Tourbillon and the mid-bass, while less in quantity, seems even more articulated than Tourbillon’s. Towards the end of the song, the cymbals become more intense and Alba is doing a great job conveying them in an open space, with plenty of air.
DX1 impresses with its mids forward approach. It has a fairly reference sound, no V shape here. I have the impression that technically it is superior to the other two. The bass is more textured, without necessarily being more muscular. The amount is just right, no more, no less. The quality of the treble is over the other two, even if in terms of air it cannot compete with Alba. The instrument separation is less clear than Tourbillon, it has a flatter sound, no doubt partly because of its rather linear tuning.
Mk10 is here to prove things are never simple. It has a better balance, in the sense that the bass is a hair less powerful while retaining the texture and articulation. Since Brandee is first and foremost a harpist, this is the instrument that takes the centerstage and it sounds clear, even if a tad cold. There is just a little bit of harshness in the upper notes, but the cymbals make you forget it.

Eminem – Without Me
A classic by now, this piece brings the best out of Tourbillon. The combination of mid- and sub-bass makes this a particularly appropriate choice for Tourbillon. The words can be understood with ease, the voice is reasonably detailed, and comes across with a certain degree of clarity. The bass line is king—fat, textured with good rumble, and with an impact that is, as expected, more towards medium than good.
Alba has just a touch too much treble here. The bass is great, even though not as rumbly as Tourbillon, it has very good impact. The voice is one step clearer and once more Alba shows great style.
Special guest: FatFreq Deuce. Despite its rocky launch, the Deuce is one of my most loved IEMs. Well, it plays in a league of its own, as this is my “bass-head” IEM. It sells for a little over 200 EUR, but what it brings to the table is massive bass, good balance, vocal clarity, and a larger stage. The bass reaches deep, but this is not what impressed me the most; it is the impact. When it hits, it does it like a sledgehammer. I am sure there are better bass-head IEMs out there, but for this price, I think it is difficult to beat.
Special guest 2: Tangzu YuXuanJi. Good bass in quantity, but less so in quality, as it sounds a bit flat and lacking articulation. The voices are very clear, but also lack body, sounding thin and a bit metallic. The treble is pretty much the same: thin, lacking articulation and details. This is a simple recommendation: Tourbillon.
Birds ov Paradise - Ängarna
Simple track, almost no voice, if you don’t count the little synthesizer line. It plays on stage and stereophonic effects. It’s done well, as there is always a tiny difference between L/R; that doesn’t require much attention, the effect is pretty obvious. Tourbillon does not leave me feeling there could be more to it, but let’s see how the other two are doing.
Alba is perfectly balanced; there is no hint of shoutiness, nor overwhelming bass. Just simple, great, enjoyable sound. Certainly a more spacious presentation, with equally good sound density. I have no favorites so far. Either of them is perfectly suited for this, with Tourbillon having more bass and Alba sounding more open.
DX1 has many talents, but this track is not necessarily one to reveal them. No major faults, but the flat tuning does not work here; I want booming bass, not this overly technical but relatively lifeless approach. Adding a touch more bass elevates DX1 dramatically, but as it is, it lags behind the other two.

Lusine – Not Alone
This not being one of my preferred genres, I do not have particular pointers I am looking for. Tourbillon sounds spacious enough, this kind of music being less taxing than prog metal. A pleasant surprise is the tall stage. It’s not deep, but the height, combined with the way the instruments are separated, gives the impression of space. A bit like placing a mirror in a small room to make it look bigger. There is good balance and good coherence. This little IEM is starting to grow on me.
I had expected to like Alba more, me being a treble head... well, it does sound more crystalline and with a larger stage, but truth is, the treble is just a bit harsh here. The extra air is great, but there is a spot in the mid-treble causing them to be just a bit strident and forcing me to lower the volume. This caused the bass to take a hit, which, in turn, exposed that treble again... once the right volume was found, I had no problems enjoying the music. I simply preferred the darker approach for this song.
DX1 – the same as for the previous song. More technically capable, but I need more bass and a touch of warmth to really appreciate this music.

Olafur Arnalds – So Close
(From the Broadchurch soundtrack). A harrowing track from a harrowing series. Very atmospheric; you can almost feel the breeze of the sea and hear the seagulls. There is a palpable sense of drama. Technically, the Tourbillon is perfectly capable for this kind of music. Apart from a broader sense of space, there is little extra I could ask for.
Alba offers a clear step up. Not only is the stage larger, but it is also better filled with sound, with percussions moving gradually from left to right in a very dramatic and impactful way. Even the voice benefits from the additional force in the treble region. An additional layer of emotion seems to have been unlocked.
DX1 has a lot of potential and it can be seen, or heard here, but it comes with a big handicap (for me). It is hardly possible to find a fit stable enough to last until the end of the song. Because of these issues, combined with its naturally brighter tuning, I clearly prefer the other two. Besides, it is borderline shouty for me on this track.

General Impressions and conclusions
One of the most pleasant experiences with Tourbillon Pro was listening to Therion’s Leviathan. The bass is nice and deep, while having a slight mid-bass lift and a slight darkness in the treble. Think of it as a V tuning with a twist in the treble. Despite not having a large stage, most of the time you don’t feel it, thanks to the many voices on this record and their tasteful layering. It gives the impression of a much larger stage than it actually is. The operatic voices are rendered with average clarity, but with a bit of warmth and, frankly, quite organic. The meandering of that bass guitar is helping me forget the treble that is only average, with plenty of details well hidden. Like most single DDs, the timbre sounds very accurate to my ears.
What is it good for? One particular use struck me: evenings or night sessions. It’s a calm-sounding IEM, soothing to some extent. Despite having decent attack (the speed with which the peak intensity of the sound is reached) and fast decays, Tourbillon sounds a little bit sedated. Thanks to this sound, I find it the perfect companion for winding down. Dim the lights, play some symphonic metal.
That is not all, though; during the day it is useful for commuting, with better-than-average sound insulation and its muscular bass blocking most of the surrounding noise.

As for music, it works very nicely with all things gothic, provided the album is not produced with a complete disregard for treble. Acts like Tiamat, Therion, Paradise Lost, and other droning or menacing music sound great on them.
Where they could be better: The level of details is just not up there with its competitors, Alba and DX1. It’s polished, but the other two are simply better. The difference is not night and day, but dynamics are reduced compared to better sets. I’m not going to ask for more treble, as I love Tourbillon for what it is. I have enough bright-ish sets; this one serves me right as it is.
For their low price, they do a wonderful job. The only question is whether there is room in your collection for a set that trades some details for an enveloping warmth. If the answer is yes, I can certainly recommend them. If you are looking for a brighter sound with roughly the same bass experience, the Mk10 is available for about the same price and it gets my recommendation.
Yes, increasing the budget brings more sound quality. Whether that quality is worth it is entirely up to you.
Thank you for reading.