14mm of Dynamic Power with FST Technology
How good can a dynamic driver be in a custom IEM I asked my friend. He said he wasn’t sure, but from the reviews they sound like they have potential. We agreed that in the world of universal IEMs the dynamic driver is the driver of choice for most manufacturers, especially on the lower end and as you go up the price scale things start to shift. Once you get to custom IEMs balanced armatures rule, however the use of dynamic drivers is increasing.
So, how good can the Wan Xuan (Beat Audio) wx i9pro be? We agreed there is a good possibility it could stack up well in for the price, but the sound would probably be different than BA driver IEMs in the price range. There are design challenges with multi-BA designs such as driver matching and note thickness which translate to various sound characteristics that are not adored by all while at the same time dynamic drivers can exhibit some unfavorable results such as imperfect control and bass bleed, especially with lower end sources. Of course there are exceptions from top to bottom such as the GR07 which has nice control and a flat signature, the EX1000 which has BA qualities both good and bad, and the SM3 with a thick and reverberant note. Moving to custom IEMs you can throw out these preconceived notions of BAs you would have from universals as the BA sound can be made to sound very close to the reproduction of a dynamic driver, but still not exactly the same.
Leading to this review to see how the i9pro stacks up with its single 14mm dynamic driver, the largest dynamic driver custom IEM to date. There is competition out there including the original single dynamic driver custom manufacturer, Future Sonic, and several hybrids ranging in price from less to more than the i9pro including Thousand Sound, Unique Melody, Rooth, and EarPower, not to mention another Wan Xuan model, the wx i9.
The summary review of the i9pro and all other custom IEMs I have reviewed along with links to full reviews can be found here.
How to Order, Warranty, Options
For those in the US, you can order from custom-IEM.com here. Stephen makes it easy to get your i9pro and handles everything. For those in China, you can order from here. The price is $669, but there is a launch promotion for only $589 from custom-IEM.com! The deal may be over, but contact Stephen.
NOTE: The 14mm driver will not fit in all ears, contact Stephen from custom-IEM.com to make sure the i9pro will fit your ear.
Options: Color: clear, translucent black
The wx i9pro uses a single 14mm dynamic driver in each channel. There is a vent hole in the back center of the shell and a single, very large sound tube with a small channel between the rear driver chamber and the sound tube containing a filter. The cable uses the beat audio style ear hook and has an inline metal can with FST on it. Overall the shell is very large in depth in comparison with other custom IEM shells I have, and I can’t imagine it is that way due to my ear impressions.
The i9pro comes with a Dolfin box case that has an inner lining and a cleaning tool. The Dolfin box is nice and comparable with Otter boxes.
The cable uses the typical Beat Audio style ear guides and the initial look and feel reminds me of a lower quality Cronus. The metal can located about 4.5″ (114.3mm) from the straight 3.5mm plug measures 1.68″ (42.68mm) long by 0.4″ (10.39mm) and has strain relief on both sides. This makes the replacement cables limited if you want the FST electronics. The right shell connector is black and the left is silver. After extended use the cable did become tangle prone, at least much more so than other stock cables.
I did try the i9pro with the Whiplash TWag cable (I don’t own any aftermarket Beat Audio cables) to see how the i9pro performed without the FST technology. As far as the sound goes, the stock cable has a good deal more forward projection and overall spaciousness than the TWag. While most of the time the stock cable sounded great, sometimes the instrument placement sounded off in comparison with the TWag. This only occurred with very spacious tracks, and not all of them, placing something that is normally off to a side more in the middle. Bass and treble with the stock cable are accentuated, especially the bass which hits harder but doesn’t sound as clean. Imaging is better with the TWag with a more balanced sound across the frequency spectrum, but the stock cable is more spacious.
Overall the shell build quality is great and there are no visible bubbles or imperfections in the shell with a nice finish. The cable sockets are flush and the pins aren’t quite as tight as they should be in my opinion. The cable does come loose with use and I even had a shell separate during A/Bing. This can be fixed by slightly clamping the pins with pliers. Also, over time the cable that for the left shell connector was able to spin around and often the cable was not at the correct angle when I started to insert the i9pro.
Being that the i9pro is vented it doesn’t provide quite as good of isolation as the typical sealed shell custom IEM. This is noticeable with no music playing, however when music is playing the leakage seems to be reduced, even at quieter volumes and isolation in noisy environments is only slightly lower than something like the X3 and better than the Fabs.
The i9pro received 200+ hours of burn in as is customary for my dynamic driver IEMs before I do my serious listening. You can read about my testing technique here and my review thoughts on how to read a review here. I compared the i9pro with several custom IEMs in the price range including the Thousand Sound TS842, Kozee Infinity X3, Minerva Mi-3, Fabs Fabulous Earphones, Starkey SA-12, and Dream Earz 5X.
When I first heard the i9pro I thought that the amount of bass was, well, immense and I was surprised at how the soundstage sounded different than I was used to as I just finished the UERM review. I thought the soundstage presentation was off as some of the more spacious tracks I have just didn’t sound right. So the i9pro went back to the burn in rig before I commenced my listening. I also did try an aftermarket cable and noted my results in the cable section above.
Bass: Having a 14mm dynamic driver screams bass and the i9pro delivers with plenty of enhancement. The level of enhancement is below the JH16 and Infinity X3, as in the sense of continuous enhancement no matter the track, but it can equal and even surpass both of those with the quantity of bass depending on how much bass there is in the original track. Sub-bass rumble is very prominent when needed and the i9pro can make me cry for bass mercy with some songs such as Ormatie – Twisted Turns with a moderate volume. However, with a song like Blue Rodeo – 5 Days in May the bass is only slightly enhanced, which is welcome. The i9pro is a bass amplifier, the more that is there, the more it is amplified!
Texturing of the bass is good and reverberation levels are high, however the FST technology does add to the bass and in doing so results in a lack of control found in the TS842, EP-10 Plus, and BA custom IEMs, not to mention the i9pro with the TWag cable. Bass detail is very good however when the volume is turned up the bass becomes bloated and starts to bleed into the mids. Luckily this only occurs at a louder volumes than I would ever listen at other than for testing purposes. The i9pro can move significant air in the bass region and does offer a combination of bass and sub-bass only matched by the more expensive EP-10 Plus. Depth is not a problem as the i9pro starts to gently roll off in my ear at 27 Hz, but I can still fell a bass sensation with a 12 Hz test tone.
When at moderate and below listening levels (which is highly recommended for your own long term ear health) the i9pro has good dynamics. Thickness of the notes is a little higher than the RE272, FX700, and TS842 dynamic drivers while also being thicker than the BAs in the price range, but it is by no means overly thick. There is a natural timbre with real drums and the i9pro can pump out bass with electronica. Mid-bass is also enhanced, although not as much as the deep bass and mid-bass is less than the IE8, EM3 Pro, EP-10 Plus, etc. The better the source used the more controlled the bass will be, but the FST technology only allows the bass to tighten so much. If you want less enhancement and tighter bass you can use a cable without FST, however you will trade in the spaciousness.
Midrange: The i9pro has an interesting midrange as it is very pleasant, rich, liquid, and detailed with a placement that can vary drastically with each track. Overall the placement is somewhere between laid back and somewhat distant depending on the track. In this price range there is really nothing with a similar presentation to the vocals and the closest is the Mi-3, which has great forward projection but that is different than what the i9pro does. The upper midrange is slightly recessed in comparison with the midrange and treble resulting in absolutely no chance of sibilance and S’s that are sharp in the recording such as In This Moment – All For You come across almost like the singer has a lisp, but there is no hint of sibilance. Piano, guitar, and other instruments that are in the lower midrange region sound great.
While the midrange has a nice level of detail, the detail is presented differently than with the BA counterparts as the details are generally quieter and not quite as separated within the presentation. The detail is higher than the SA-12, Mi-3, and on par with the Fabs and X3, but giving ground to the TS842 and 5X. Clarity is not bad, but it is not on par with the BA counterparts due to the dynamics and the slightly recessed upper mids.
Treble: This part of the spectrum that is very good in a way, but there is an issue. The treble is presented is presented well with great note decay, impressive levels of detail, and a very natural sound with most instruments, but the issue is the treble starts to roll off fairly quickly after 13KHz. This does not affect most music but it does affect some music that are well mastered and have instruments with high energy harmonics such as cymbals or electronic that adds treble reverb such as Nelly Furtado – All Good Things (Kaskade Radio Remix). But, the i9pro does not sound dark, far from it and I still think the treble is extremely enjoyable and not as dark sounding as the SM3/UM3X/W3 but not as bright as the TS842/SA-12. What is presented is presented very well and I am very happy with the presentation.
Presentation: First, the soundstage is not typical IMO as the FST electronics change the soundstage placement and enhance the bass and treble to improve the space, which is very good for this price range. The downfall is that with very spacious tracks the placement sometimes seems to get wrapped back into the middle of the presentation resulting in an odd sound, as happened with the Chemical Brothers live at Coachella for example. However, more often than not the soundstage presentation is more spacious than the competition with proper placement. The Infinity X3 matches with width but is compressed in depth comparatively while the Mi-3 has a similar space, but that space is projected forward.
From an overall frequency response perspective the i9pro is bass heavy, warm, and has a good balance between the midrange and treble. The overall sound is on the laid back side and the midrange is slightly more laid back than the bass and treble. Note presentation has a very natural attack and decay with very good timbre for natural instruments. There is speed present in the 14mm driver, but the FST processing seems to slow things down a little bit in comparison with other custom IEMs when playing Nightwish and other faster metal. The coherence between frequency bands is excellent as would be expected from a single dynamic driver, which isn’t the case with the hybrids I have heard as there is a transition in note presentation between where the dynamic driver stops and BAs begin in note presentation.
Clarity is good for the sound signature, but the details aren’t quite as apparent as with the BA custom IEMs I have. But, the warmth doesn’t take away from the clarity as much as the note thickness and especially the slightly recessed upper mids, but conversely the very good level of detail does add to the clarity. Overall the presentation of the i9pro is very pleasing.
Thousand Sound TS842: When switching between the two in A/B testing there are quite a few differences, but they do share a very similar presentation in the bass. The i9pro is more spacious yet more forward giving the brighter TS842 a more laid back sound. Even though the midrange of the i9pro is more forward than the TS842, the TS842 articulates details better with more clarity but with a rougher note at the same time. While there is a good amount of difference between the upper midrange, the treble is surprisingly not too far off between the two. The i9pro has a smoother presentation that gives up slight levels of detail and isn’t quite as forward as the TS842 treble. The treble of the i9pro sounds more realistic in tone and note thickness however it doesn’t have the air the TS842 has. In the bass region both have dynamic bass sound but the i9pro has more rumble, emphasis, warmth, and punch at the expense of a little less control. Those that want big bass and warmth will get what they are looking for with the i9pro while those that want a more balanced and tighter bass presentation will prefer the TS842.
Going from the TS842 to the i9pro, as mentioned above, does give a better sense of spaciousness and openness. Instrument definition and edge is more precise with the TS842, even though the edge is rougher with the TS842, but placement is more realistic with the i9pro most of the time as the TS842 soundstage sounds a little flat in comparison. In summary, the TS842 is more analytical, thinner and clearer while the i9pro is more of a warm, spacious and musical presentation with more bass emphasis.
Kozee Infinity X3: From a presentation standpoint the X3 has a more mid-forward presentation with up front vocals vs. the more laid back i9pro. Clarity is very close, but the X3 edges out the i9pro due to more emphasis in the upper midrange. The X3 has a spacious soundstage which is about on par with the i9pro, although the i9pro can offer a better sense of space depending on the track and sounds more 3D most of the time. Detail levels are overall similar and notes on the i9pro are thicker by a bit resulting in a richer sound. The X3 is punchier but dynamics are similar.
Treble on the X3 is more forward and also not as smooth or forgiving, resulting in a harsher sound that has a slight grain in comparison which is brought to the forefront due to the presentation. Midrange is more emphasized with the X3 with a bump in the lower and upper mids which can sound a little artificial in comparison with the i9pro. Bass quantity of the X3 is slightly more than the i9pro, however when there is a lot of sub-bass rumble the i9pro outperforms the X3 and sounds more effortless in general to the slightly processed sound of the X3.
Overall the i9pro has a more realistic tone for real instruments while the X3 has a more enhanced and exciting sound with electronic music, not that the i9pro sounds bad with electronic music. The sense of space and power are better with the i9pro. These are similar and could be considered competitors, especially for people that listen to electronic music, in which case it would come down to a desire for a punchier and brighter sound vs. a more laid back sound with more sub-bass capability.
Fabs Fabulous Earphones: The Fabs are have a mid-forward presentation that allows the mids to remain in focus as the treble and bass are unassuming while the i9pro adds quite a bit of bass to the presentation in comparison. This presentation difference give the Fabs more apparent detail and better recreation of ambiance in the midrange area. The treble of the i9pro is more prominent with more details in cymbals and other upper midrange/treble region instruments. Bass is different in quantity but fairly close in quality, however due to the quantity in the i9pro the details are brought to the forefront. The i9pro has significantly more sub-bass rumble.
Both are similar in midrange dynamics however the i9pro is superior in bass dynamics and a little better in treble dynamics. Presentation size is similar but the Fabs sound more accurate in presentation of depth and height. The Fabs have better tonality through the midrange but the bass tonality of the i9pro sounds more accurate.
These are more a compliment to each other than a competitor as the Fabs would suit someone that has spacious vocal presentations while the i9pro does better across a wider range of genres. Bass power is definitely different as is treble presentation and the laid back feel of the i9pro is a contrast to the mid-forwardness. Technically they are fairly close.
Minerva Mi-3: While these two are close in many ways and the presentations sound similar at first, the Mi-3 has more forward projection and sounds as if you are further back in the audience of a performance. With something very spacious like Balmorhea the Mi-3 can convey a sense of depth in the presentation the i9pro doesn’t and while the i9pro is spacious, the Mi-3 can sound more spacious due to the more laid back sound. The i9pro reproduces a little more detail and has better dynamics resulting in a livelier sound to go with better coherence across the frequency spectrum. The Mi-3 has a little better transparency due to the presentation and superior instrument separation.
The bass region is vastly different as the i9pro is more enhanced with more capability, pretty much outperforming the Mi-3 in just about everything except texturing, which is a little better with the Mi-3, and control. The i9pro is warmer and has a little more thickness to the note, but with more speed than the Mi-3. Mids are similar in tone but the mids are more in your head vs. at a distance. There is a little more treble emphasis with the i9pro to go with a more forward presentation that has more detail although the Mi-3 is more extended and has a more liquid treble.
Overall, if you want a good amount of bass the i9pro is your choice while if you value forward projection the Mi-3 will be a great choice. The i9pro does offer more punch, dynamics, speed, bass, and detail while the Mi-3 is more transparent with better placement and separation of the inner parts of the soundstage.
Starkey SA-12: The first thing I noticed is the difference in the size of the presentation (spacious track) as the i9pro presents with a larger presentation. Depending on the track and even certain parts within a track they compare differently. The SA-12 is consistently 3D with decent size that doesn’t change much (changes more with amps than anything else) while the i9pro can sometimes have good 3D spacing and other times seem to flatten out the presentation, although it is always wider than the SA-12. Detail levels of the i9pro are a little higher than with the SA-12 and there is more ambiance and presence within the soundstage most of the time. While the SA-12 has better clarity, the differences are not all that large but the SA-12 is more transparent.
Bass is more reverberant, enhanced, and powerful on the i9pro but with an amp like the iQube the SA-12 isn’t a slouch. The bass presentation between the two is different as the SA-12 is tight and well textured while the i9pro conveys more power and isn’t quite as precise. While the SA-12 can reproduce sub-bass, the level differences can be significant and both share a warmth that is not at all overpowering and definitely not thin. The midrange tonality of vocals differ as the i9pro has less upper midrange emphasis than the SA-12 resulting in warmer sounding vocals that are more distant sounding than the more up close and personal SA-12. Treble is presented not all that far off in ways but the differences are fairly large as the brighter SA-12 is more extended but not as detailed giving a different feel to the treble. There is more overall note thickness with the i9pro giving piano and other instruments a richer sound, but the SA-12 isn’t thin by any means.
This choice comes down primarily to sound signature preference as well as size difference since the i9pro is much bigger than the canal sized SA-12. If size doesn’t matter, the i9pro will satisfy bass heads and soundstage space junkies while the SA-12 gives more air and a tighter overall sound. The SA-12 does isolate a bit better than the i9pro.
Dream Earz aud-5X: Differences between these two are fairly significant as the 5X is more up close and personal with a larger emphasis in the upper midrange leading to more clarity and a brighter sound. The bass of the i9pro is a little more enhanced, but the 5X isn’t a slouch close in the lower registers. Surprisingly the 5X can keep up in the bass department in most songs, but there is a tonal and tightness difference between the two. However, the sub-bass is more pronounced with the i9pro, exhibited for example by the foot tapping at the beginning of Eric Clapton – Layla (unplugged).
Midrange differences boil down to a brighter vs. warmer presentation and so for vocals it is a matter of which tonality do you prefer, however the 5X does have more detail and ambiance in the midrange. Due to the FST the i9pro can have better ambiance than the 5X, but sometimes it flip-flops as the 5X has a more accurate placement and sound such as The Chemical Brothers live at Coachella. The upper midrange emphasis is blended into the treble, giving the 5X a little more treble emphasis to go along with more extension. While the treble is similar in amplitude and presentation, the i9pro has an overall more liquid and slightly more detailed treble than the 5X, however there were many instances where the treble sounded dark in comparison due to the roll off of the i9pro.
While not analytical, the 5X has a thinner note with a brighter sound, making the i9pro warmer in comparison. The location of the performance is more distant with the i9pro, making the 5X sound closer and more intimate in comparison, but the i9pro wins in overall spaciousness even though the 5X isn’t bad at all. The 5X does have more speed and an overall more accurate and analytical sound vs. the i9pros more fun sound. Either of these can please a bass head, but the i9pro can recreate much more overall bass and is often much more bass heavy.
Volume performance: The i9pro is good at low volumes but the bass levels are lower, probably due to perception from human loudness curves. Due to the sensitivity there more than likely won’t be many issues with sources that have analog volume controls. The biggest issue I have with the i9pro as far as volume is at louder volumes. For whatever reason, the driver becomes uncontrolled and when there is a lot of bass it bleeds to the midrange. This isn’t an issue for me as I don’t listen at volumes that will cause the issue (and I highly recommend you don’t listen that loud also), but it is there if you crank the volume.
Sound Summary: The i9pro has a warm, rich, powerful sound that is not lacking in any way except the treble extension which is only apparent when compared with airy headphones. The spaciousness is uncommon due to the FST technology which moves the bass and treble back creating the sense of additional space and adds bass punch. For example the Infinity X3 has similar width but the depth is shallow in comparison and the Fabs, which have a fairly spacious presentation are noticeably smaller all around. The FST can at times result in instrument placement being a little off when compared with my other custom IEMs when there is an extremely large spaciousness in a track, but this doesn’t occur often.
The quality of the bass is good but due to the FST enhancement the control isn’t quite as good as with my other hybrid in the price range. However, bass heads will most likely prefer the i9pro as the bass is enhanced. The note presentation is very natural and fairly coherent from top to bottom with thickness that isn’t overly thick, but due to the bass performance with the FST the i9pro is a little slower in the bass region. With the natural presentation, enhanced bass, and added spaciousness the i9pro is good with most genres and especially today’s music that isn’t mastered with the most spacious sound.
Portable Sources, DAPs
Clip+: No complaints about the Clip+ for the price/size as it performs quite well with the i9pro. Bass isn’t the most controlled, but it isn’t bad considering the Clip+ does accentuate the bass to an extent. Even at louder volumes, while not perfect, the Clip+ performs decently. 4/10
iPhone 3G: The 3G is a little more spacious and has a little more clarity than the Clip+, but the bass control is a step down and when there is a decent amount of bass the lack of control interferes with the rest of the spectrum. 2.5/10
RoCoo-A: Compared with the Clip+ the RoCoo has less sub-bass and bass but the clarity is a little better with an overall brighter presentation. The size of the space is fairly close and the rest of the presentation isn’t all that far off. There really isn’t any advantage to the RoCoo with the i9pro vs. the Clip+. 4/10
AMP3 Pro2: When going from the RoCoo to the Pro2 the first thing I notices was the hiss. Sure, the overall sound is higher quality with more separation, a more 3D presentation, and a more natural sound with better note decay but the hiss knocks the score down. 4.5/10
Studio V (BA firmware): The V takes the sound of the Pro2, increases the naturalness to the sound and removes the hiss, but the weakness is the bass depth. It has bass punch, but the depth is not the same as with the Clip+. Overall the sound is between the Clip+ and the modded iPod->amp. The score is reflective of the single unit design. 6/10
801: The 801 adds dynamics and punch to the music and is the best of the portable players I have tested. While it doesn’t offer the driver control of most of the amps nor quite the clarity and transparency, it isn’t all that far off and contained in one module. There are volume imbalances at very low volumes. 8/10
Portable Sources, DAPs with Amps
Modded iPod ->
Arrow 12HE: The 12HE is an average performer among this group, not doing anything better but not being the worst. Soundstage space is about on par with the Pico Slim and clarity is between the Slim/120 and iQube. There is a slight channel imbalance at very low volumes. 6/10
Pico Slim: A tad bit less spacious than the uHA-120 and iQube but with more clarity than the iQube, although there is less bass. Control is on par with the 120 as is transparency and a brighter top end. 7/10
uHA-120: Very good combination with control, spaciousness, detail and clarity. There is a good deal of bass punch compared with the Pico Slim, but still a little more clarity and a brightness the rest of the amps don’t have save the Pico Slim. The transparency is on par with the Pico Slim at the top of this group of amps. While this is the best sounding amp with the i9pro, there is a channel imbalance at low volume levels I didn’t experience with the other amps. This imbalance is rather minor to me so I only reduced the score 1 point. 8/10
iQube: Not quite as clear as the uHA-120 and Pico Slim as the iQube doesn’t seem to control the i9pro driver quite as well. The space is the largest of the amps I tested, besting the next closest 120, but there is less overall transparency with a little thicker sound than the rest of the amps. 7/10
Neco V2: coming soon
D10: Spaciousness of the Pico Slim with clarity about the same as the iQube and bass slightly less controlled compared with all the other amps resulting in less transparency with bass heavy music. There is a very minor channel imbalance at very low volumes. 5.5/10
HUD-MX1 (OPA1611 & power supply): The MX1 is ever so slightly less detailed and a little less dynamic than the other DACs tested with the i9pro. The presentation of space is on par with the 801 and the sound signature is fairly similar to the other DACs. The exception is the deep bass doesn’t have the same power and is a little weaker than with the iQube, 801, and D1, all of which cost significantly more. There is a channel imbalance at lower volumes. 6/10
D10: The D10 has the smallest space of the DACs tested by a bit and the bass is similar to the MX1, but there is a little more resolution than the MX1. Space with some track is slightly smaller than the MX1an 801, but with most tracks it is just about the same. There is a slight channel imbalance at very low volumes. 6.5/10
iQube V2: The V2 has the best space of the small and portable/transportable DACs with an added sense of depth to the presentation. This DAC sounds a little different than the rest in frequency response with a shift to a bassier presentation accentuating the great and deep bass of the i9pro. Resolution is about on par with the D1 except with 24 bit material. 9/10
801:The 801 brings out the best of the treble of the i9pro without much sacrifice elsewhere. Due to the slight enhancement in the treble the 801 gives a little more detailed presentation. Deep bass impact is very good and on par with the iQube, although not as accentuated. The 801 has good depth, but not quite up to thelevel of the iQube or D1. There is a channel imbalance at very low volumes. 8/10
D1: The D1 is about on par with the iQube in many tracks, but when a bass heavy track comes on the bass becomes too much and sounds bloated, which is more due to the FST technology working to enhance the already enhanced bass. Songs with less bass sound ever so slightly more 3D with the D1, but the improvement over the iQube is minimal. 7/10
Source Summary: The i9pro has the ability to resolve more detail than the entry level DAPs such as the Clip+ and iPod, and even the RoCoo and Studio V can output, so using an 801 or decent DAC will reap some benefits. Amps also help, but to do the FST, only to a point. If an amp strengthens the bass too much the FST will cause the bass to be less controlled affecting the sound in a negative way as happened with the Anedio D1. The 801 is overall a very good match, but due to the price something such as an iPod/iPhone to the uHA-120 via LOD will be a great compromise between price and performance.
FST technology gives the i9pro a pretty unique sound in its price range with added spaciousness to go with the sound of a dynamic driver. The spaciousness comes with enhanced bass, an overall warm presentation and a great treble quality. The level of enhancement is high with punchy and deep, rumbling bass. Detail levels are good for the price range and presented in a liquid and enjoyable way. Note decay sounds very natural but speed is average. Piano sounds amazing, D&B bombastic, and most genres sound right. Midrange tonality is on the warmer side.
But, with the good comes some issues including treble roll off at 13K which can affect air and not recreate some of the harmonics and spatial queues that give ambiance to the upper end. FST increases the bass and this can lead to the bass sounding a little uncontrolled at times, and the added spatial qualities can affect instrument placement for very spacious tracks. However, even with these issue the overall presentation of the i9pro is very enjoyable and without direct comparison you will most likely be hard pressed to hear the issues. So go ahead, rattle your brain with 14mm of dynamic driver that give you a nice spatial experience.
– Very good, enhanced, dynamic bass that reaches deep at moderate and below volume
– Treble quantity is in a sweet spot and is very detailed
– Spacious presentation
– Instrument placement can sometimes be off
– FST technology in the cable limits aftermarket cable choices