Disclaimer:
I bought this IEM at my own expense from Aliexpress when it was on sale and am not affiliated to any company.
Introduction:
I was searching for a good single DD driver IEM and am pleased to have bought the Nine Tails. It is a very well tuned single DD driver IEM, and the sound signature can be customized with many filters. This IEM has a cult following with generally good reviews, but hasn't gotten much mainstream attention, probably due to its very unconventional design.
The Nine Tails in actual fact is a Far Eastern "fox spirit" in Japanese, Korean and Chinese cultures, which can shapeshift to take the form of a human. Do the customizable filters let it live up to its namesake in changing the sound signature?
Here's my short review on it:
Specifications:
- Driver: Single Dynamic Driver
- Impedance: 16Ω
- Sensitivity: 100dB
- Frequency Response: 5 – 40,000 Hz
- Cable: MMCX detachable cable
Accessories:
Other than the IEM, it comes with:
- 1 detachable silver-copper MMCX cable
- 3 different pairs of rear filters, 3 different pairs of front filters
- 1 small pouch
- 1 shirt clip
- 2 pairs of foam eartips
- 3 pairs of black silicone eartips, 3 pairs of white silicone eartips
Build/comfort:
Let's get the big elephant in the room out of the way: the design is extremely unconventional to say the least. It took me a few tries to finally figure out how to put it into my ears. It is actually worn like a conventional overear IEM, but with the gourd shaped part downwards and the narrower tip of the gourd facing upwards at about 10 degrees anteriorly.
It is actually very comfortable once you get a good fit in, and very light. It is made of alloy and is very sturdy.
I suspect a lot of potential buyers might be put off by the design, fearing that they may be uncomfortable or not be a good fit, but I can assure you I have average sized ears and have no issue wearing it for hours.
Isolation:
IMHO, this is one of the weaker isolating IEMs, and I tried using it outside, but it failed to really prevent external noise from disturbing my music. I would personally only recommend it for use at home.
Filters:
I can assure you the filters ain't a gimick and they actually do change the sound signature. Based on my listening, the filters do the following modifications to the sound:
a) Silver filters - comes by default on the Nine Tails. Makes the sound V shaped.
b) Red filters - boosts the bass. I felt it does cause a mild mid bass bleed and muddiness when these were used, but it does pump up the lower frequencies by a few DB that is noticable, and is good for EDM. I would say it is just a level shy of true basshead levels when both front and rear filters are red.
c) Blue filters - makes the bass less pronounced but makes treble more extended and airy. I would say it makes the Nine Tails quite neutral sounding with it on.
There are both a front and back filter so they can be used independent of the coloured filters (ie u can use a blue front filter with a silver back filter etc). Generally it would make sense to use the same colour for both the front and back filter, or at least a silver one with either the blue or red. This makes many permutations for finetuning of the sound you want. In view of the three pairs of both front and back filters, there really are nine combinations of sound tuning one can tune the Nine Tails to, so it does live up to its namesake. In between the extreme both blue filters on one end, and the both red filters on the other end, the rest of the filter tunings are subtle changes along this spectrum.
Personally I liked both filters as silver for my general listening. Sometimes when I'm in a basshead mood, I'll use both red filters.
I've read reports in a the forums that the filters can drop out and be lost easily, but personally I haven't had the filters drop out on me, after screwing it on securely.
Sound:
I tested this with a Desktop -> Khadas Tone Board -> Fiio A3 and Android -> Tempotec Sonata HD. The Nine Tails is quite easily drivable from smart phones without any need for external amping. I didn't have any hiss with this IEM on laptops/PC/smartphones. It definitely scales better with a DAC/AMP.
Even on the most neutral tuning, it is mainly a V shaped tuning, with recessed mids.
I found the clarity and details/instrument separation to be very good for a single DD driver, just slightly worse than my other single DD driver IEM, the TFZ No. 3. But it would lose to some multi BA/hybrid IEMs in this area.
Bass:
As above, you can fine tune the sound signature with filters, but in general the Nine Tails bass is very typical of a well tuned DD driver, with good subbass extension and displacement of air with either the silver or red filters on. With the blue filters both on, the bass sounded neutral to me. With both red filters on, it is just a level shy of true basshead levels.
Mids:
Quite recessed, typical of most V shaped CHIFI tuning. I would have preferred a bit more meat in the mids personally. Nevertheless, the mids are detailed with good clarity and instrument separation. The timbre of voices and instruments from the Nine Tails is very organic and natural, one of the best I have heard in my collection of IEMs.
Treble:
Extends well with no fatigue/harshness/sibilance. Very good for listening for long sessions and having a relaxing listen. I would class it on the slightly darker side compared to the usual bright CHIFI treble tuning.
Soundstage:
Above average.
Comparisons:
a) Audiosense T800
As expected of a 8 BA driver IEM, the T800 trumps the single DD driver Nine Tails in the details/clarity/resolution/soundstage/instrument separation department. The clarity and details of the Nine Tails is no slouch, but the T800 is on another level.
The T800 is much more bright on the treble and may cause a bit of issues for the treble sensitive among us. Whereas the Nine Tails treble is very polite and non fatiguing and relaxing.
The mids are more recessed on the Nine Tails.
Although it is a DD bass, the bass (with red filters) of the Nine Tails is almost on par with the vented subwoofer BA bass of the T800 (IMO the BA bass of the T800 sounds very much like a DD bass).
b) TFZ No. 3
This is a more fair comparison as both are single DD driver IEMs.
The clarity and details is marginally less on the Nine Tails.
Imaging is sharper on TFZ No. 3.
Treble is slightly brighter on the No. 3 especially the lower treble. There is a roll off at higher frequencies for both of these IEMs.
Mids are more recessed on the Nine Tails, with less meat to vocals/instruments.
The TFZ No. 3 bass and subbass extends deeper and has more oomph and displaces more air than the Nine Tails (with red filters). I personally find the No. 3 to have the best bass in my stable of IEMs.
Having said that, with both bass filters on the Nine Tails and with a good DAC/AMP, it can hit almost close to bass head levels IMHO.
Soundstage is better on the Nine Tails.
Conclusion:
This is a great IEM that allows you to customize the sound signature you would like by changing the filters, giving many possible permutations, from a bassy sound to a more neutral signature. I hope more people would come to give the Nine Tails a try, even though it may look weird, it actually is super comfortable and well fitting.
It is very relaxing IEM to listen to, with little fatigue/harshness.
I found the isolation and mids lacking, but the many ways I can customize the sound to suit my mood or music genre more than makes up for this.
The tonality and timbre of voices and instruments are second to none on the Nine Tails.
If you are looking for a well tuned DD driver IEM, you can consider getting the Nine Tails. It may look for all intents and purposes to be an Ugly Duckling, but once you give it a try and look below its appearance, the Nine Tails may actually be a Beautiful Swan underneath it all.
I bought this IEM at my own expense from Aliexpress when it was on sale and am not affiliated to any company.



Introduction:
I was searching for a good single DD driver IEM and am pleased to have bought the Nine Tails. It is a very well tuned single DD driver IEM, and the sound signature can be customized with many filters. This IEM has a cult following with generally good reviews, but hasn't gotten much mainstream attention, probably due to its very unconventional design.
The Nine Tails in actual fact is a Far Eastern "fox spirit" in Japanese, Korean and Chinese cultures, which can shapeshift to take the form of a human. Do the customizable filters let it live up to its namesake in changing the sound signature?
Here's my short review on it:
Specifications:
- Driver: Single Dynamic Driver
- Impedance: 16Ω
- Sensitivity: 100dB
- Frequency Response: 5 – 40,000 Hz
- Cable: MMCX detachable cable
Accessories:
Other than the IEM, it comes with:
- 1 detachable silver-copper MMCX cable
- 3 different pairs of rear filters, 3 different pairs of front filters
- 1 small pouch
- 1 shirt clip
- 2 pairs of foam eartips
- 3 pairs of black silicone eartips, 3 pairs of white silicone eartips

Build/comfort:
Let's get the big elephant in the room out of the way: the design is extremely unconventional to say the least. It took me a few tries to finally figure out how to put it into my ears. It is actually worn like a conventional overear IEM, but with the gourd shaped part downwards and the narrower tip of the gourd facing upwards at about 10 degrees anteriorly.
It is actually very comfortable once you get a good fit in, and very light. It is made of alloy and is very sturdy.
I suspect a lot of potential buyers might be put off by the design, fearing that they may be uncomfortable or not be a good fit, but I can assure you I have average sized ears and have no issue wearing it for hours.
Isolation:
IMHO, this is one of the weaker isolating IEMs, and I tried using it outside, but it failed to really prevent external noise from disturbing my music. I would personally only recommend it for use at home.
Filters:
I can assure you the filters ain't a gimick and they actually do change the sound signature. Based on my listening, the filters do the following modifications to the sound:
a) Silver filters - comes by default on the Nine Tails. Makes the sound V shaped.
b) Red filters - boosts the bass. I felt it does cause a mild mid bass bleed and muddiness when these were used, but it does pump up the lower frequencies by a few DB that is noticable, and is good for EDM. I would say it is just a level shy of true basshead levels when both front and rear filters are red.
c) Blue filters - makes the bass less pronounced but makes treble more extended and airy. I would say it makes the Nine Tails quite neutral sounding with it on.
There are both a front and back filter so they can be used independent of the coloured filters (ie u can use a blue front filter with a silver back filter etc). Generally it would make sense to use the same colour for both the front and back filter, or at least a silver one with either the blue or red. This makes many permutations for finetuning of the sound you want. In view of the three pairs of both front and back filters, there really are nine combinations of sound tuning one can tune the Nine Tails to, so it does live up to its namesake. In between the extreme both blue filters on one end, and the both red filters on the other end, the rest of the filter tunings are subtle changes along this spectrum.
Personally I liked both filters as silver for my general listening. Sometimes when I'm in a basshead mood, I'll use both red filters.
I've read reports in a the forums that the filters can drop out and be lost easily, but personally I haven't had the filters drop out on me, after screwing it on securely.
Sound:
I tested this with a Desktop -> Khadas Tone Board -> Fiio A3 and Android -> Tempotec Sonata HD. The Nine Tails is quite easily drivable from smart phones without any need for external amping. I didn't have any hiss with this IEM on laptops/PC/smartphones. It definitely scales better with a DAC/AMP.
Even on the most neutral tuning, it is mainly a V shaped tuning, with recessed mids.
I found the clarity and details/instrument separation to be very good for a single DD driver, just slightly worse than my other single DD driver IEM, the TFZ No. 3. But it would lose to some multi BA/hybrid IEMs in this area.
Bass:
As above, you can fine tune the sound signature with filters, but in general the Nine Tails bass is very typical of a well tuned DD driver, with good subbass extension and displacement of air with either the silver or red filters on. With the blue filters both on, the bass sounded neutral to me. With both red filters on, it is just a level shy of true basshead levels.
Mids:
Quite recessed, typical of most V shaped CHIFI tuning. I would have preferred a bit more meat in the mids personally. Nevertheless, the mids are detailed with good clarity and instrument separation. The timbre of voices and instruments from the Nine Tails is very organic and natural, one of the best I have heard in my collection of IEMs.
Treble:
Extends well with no fatigue/harshness/sibilance. Very good for listening for long sessions and having a relaxing listen. I would class it on the slightly darker side compared to the usual bright CHIFI treble tuning.
Soundstage:
Above average.
Comparisons:
a) Audiosense T800
As expected of a 8 BA driver IEM, the T800 trumps the single DD driver Nine Tails in the details/clarity/resolution/soundstage/instrument separation department. The clarity and details of the Nine Tails is no slouch, but the T800 is on another level.
The T800 is much more bright on the treble and may cause a bit of issues for the treble sensitive among us. Whereas the Nine Tails treble is very polite and non fatiguing and relaxing.
The mids are more recessed on the Nine Tails.
Although it is a DD bass, the bass (with red filters) of the Nine Tails is almost on par with the vented subwoofer BA bass of the T800 (IMO the BA bass of the T800 sounds very much like a DD bass).
b) TFZ No. 3
This is a more fair comparison as both are single DD driver IEMs.
The clarity and details is marginally less on the Nine Tails.
Imaging is sharper on TFZ No. 3.
Treble is slightly brighter on the No. 3 especially the lower treble. There is a roll off at higher frequencies for both of these IEMs.
Mids are more recessed on the Nine Tails, with less meat to vocals/instruments.
The TFZ No. 3 bass and subbass extends deeper and has more oomph and displaces more air than the Nine Tails (with red filters). I personally find the No. 3 to have the best bass in my stable of IEMs.
Having said that, with both bass filters on the Nine Tails and with a good DAC/AMP, it can hit almost close to bass head levels IMHO.
Soundstage is better on the Nine Tails.
Conclusion:
This is a great IEM that allows you to customize the sound signature you would like by changing the filters, giving many possible permutations, from a bassy sound to a more neutral signature. I hope more people would come to give the Nine Tails a try, even though it may look weird, it actually is super comfortable and well fitting.
It is very relaxing IEM to listen to, with little fatigue/harshness.
I found the isolation and mids lacking, but the many ways I can customize the sound to suit my mood or music genre more than makes up for this.
The tonality and timbre of voices and instruments are second to none on the Nine Tails.
If you are looking for a well tuned DD driver IEM, you can consider getting the Nine Tails. It may look for all intents and purposes to be an Ugly Duckling, but once you give it a try and look below its appearance, the Nine Tails may actually be a Beautiful Swan underneath it all.