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FLC Technology FLC8

FLC Technology FLC8 Review

FLC Technology FLC8
Brief: Variable-tuning triple-driver hybrid IEM with a massive 36 possible sound settings

MSRP: approx. $350
Current Price: $350 from$350 from
Specs: Driver: Hybrid, dual BA + dynamic | Imp: 11Ω | Sens: 93 dB | Freq: 20-20k Hz | Cable: 3.9′ L-plug
Nozzle Size: 5.5mm | Preferred tips: Stock single-flanges; MEElec M6 single-flanges; Comply T400
Wear Style: Over-the-ear

Accessories (5/5) – Single-flange silicone tips (3 sizes), treble/midrange tuning nozzles (4 pairs), bass tuning ports (3 pairs + spares), sub-bass tuning ports (3 pairs + spares), keychain container for tuning parts, tweezers, over-the-ear cable guides (pair), cleaning tool, airplane adapter, 6.3mm adapter, and nice semi-hard carrying case
Build Quality (4/5) – The angular plastic housings of the FLC8 are well-made and surprisingly small considering the 3-way hybrid driver configuration. What really sets it apart from other high-end earphones, however, is the tuning system. The housings boast prominent front and rear ports, each with its own set of interchangeable plugs, as well as interchangeable nozzles. A word of caution – be careful when working on the earphones for fear of losing and/or damaging the small parts. Changing sound settings is not something I’d recommend doing on the go.

The cables are detachable, with 2-pin sockets that are slightly recessed on the cable end. Oddly, the included cable is a little on the short side, especially considering the over-the-ear fit. The 1.3m length listed in the product specifications is optimistic by about 10cm.
Isolation (3.5/5) – Good, though mild audio leakage through the vents can occur at high volumes
Microphonics (4.5/5) – Very low
Comfort (4/5) – In the standard over-ear configuration, the FLC8 is very lightweight and comfortable. Next to conventional ergonomic in-ears, like those manufactured by Shure and Westone, its nozzles are slightly unusual – wide and not angled relative to the earpieces. While maybe not perfect for those with narrow ear canals, this, together with the memory wire-less cables, allows the FLC8 to be worn cable-down as well as cable-up in some ears. The stock eartips of the FLC8 also have an unusual design and only come in three sizes but work well, perhaps reducing bass a touch compared to more conventional tips.

Sound (9.4/10) – The tuning system of the FLC8 is far more complex than any other I’ve come across, utilizing three different types of adjustment. There are four interchangeable nozzles, which control the mids and treble, three sets of plugs for the front tuning ports, which control the sub-bass, and three sets of plugs for the rear ports, which control the bass.

Altogether, this allows for 36 different sound signatures – a massive number compared to the three that you commonly get with other variable-tuning earphones such as the AKG K3003 and RHA T10i. To put it another way, if I were to A:B all of the possible sound configurations of the FLC8 against one another, I would have to perform over 600 comparisons.

I’ve summarized how each of the FLC8’s parts is designed to affect sound in Table 1 below. As always, the tuning parts work by restricting flow through the respective aperture of the earphones. They range from open ports, to various filters, to completely plugged vents. I attempted to determine the hardware setup of each part and included that information as well.

Table 1: Effects of FLC8 tuning parts

Type Color Sub-bass level Bass level Midrange level Treble level
Front Port (sub-bass adjustment) Red (sealed port) High
Gray (filtered port) Med
Clear (open port) Low
Rear Port (bass adjustment) Black (open port) High
Gray (thin filter) Med
Clear (thick filter) Low
Nozzle Filter (midrange and treble adjustment) Gold (thin filter) High Med
Green (no filter) Med High
Dark gray (thin filter) Med Med
Blue (thick filter) Med Low


Subjectively, the sound tuning filters do perform as promised for the most part. In some cases the differences are immediately audible and in others – quite subtle.

The manufacturer includes five sets of recommended combinations for the tuning parts, by music genre. These are listed in Table 2. I’ve also added my own preferred setting, which is identical to the “balance” setting save for the heavier sub-bass port.

Table 2: FLC Technology’s recommended sound setups, plus my preferred modification of the default tuning

Recommended configuration Front Port (sub-bass) Rear Port (bass) Nozzle Filter (midrange and treble)
Balance (default) Gray (sub-bass=med) Gray (bass=med) Dark gray (mids=med; treble=med)
Pop/rap Gray (sub-bass=med) Black (bass=high) Dark gray (mids=med; treble=med)
Vocal Clear (sub-bass=low) Clear (bass=low) Gold (mids=high; treble=med)
Light music Clear (sub-bass=low) Clear (bass=low) Dark gray (mids=med; treble=med)
Strings/Piano Clear (sub-bass=low) Clear (bass=low) Green (mids=med; treble=high)
My preferred Red (sub-bass=high) Gray (bass=med) Dark gray (mids=med; treble=med)


All of the manufacturer-recommended tunings can be grouped into two categories – those with flat/light bass (vocal, light music, and strings), which differ in the relative balance of mids and treble, and those with the FLC’s equivalent of flat mids/treble, which differ in the amount of bass (balance and pop/rap). My own preferred tuning falls in this second grouping as well.

In my view, then, the FLC8 is best viewed not as an earphone with 36 discrete sound signatures, but one with two or three base configurations that may then be subtly adjusted to one’s liking.

I spent some time trying to ascertain the exact effects of each set of tuning ports. I thought the light bass tunings – the clear sub-bass and bass ports – lacked a little in the way of depth and punch for my liking. The gray medium sub-bass port and the red high sub-bass port, on the other hand, provided plenty of depth and only differed from each other minutely. I ended up preferring the red front sub-bass port – the high setting.

The effect of the rear bass tuning port was more apparent. With the gray medium bass ports, the bass has very nice punch. FLC Technology utilizes the gray ports in their default “balance” tuning, but realistically the impact is greater than with a reference-flat earphone. The clear low bass port is closer in bass quantity to a flat unit such as an Etymotic ER4 or the VSonic VC1000, but I found this setting to also impact the treble curve of the earphones with my preferred midrange/treble ports, moving some of the treble peaks closer to the “sibilance” range. Since the extra bass impact of the gray bass ports doesn’t take away from the overall clarity and resolution, I find that setting to be preferable.

The black high bass port increases the impact even further, to the level of enhanced-bass dynamic-driver earphones like the Shure SE215 and Sony MH1C, albeit with better bass quality. While this doesn’t do bass control any favors, high-end earphones with enhanced bass are few and far between, so it is a welcome option. However, I thought the black bass ports, like the clear ones, caused the highs to sound less smooth and refined compared to the gray medium bass filters.

The relative levels of the mids and treble are controlled by the nozzle filters, of which there are four sets. The dark gray filters, which FLC Technology uses in their neutral setting, ended up being my favorites as the smoothest and most pleasant all around. These are said to offer medium midrange and medium treble levels.

The green high treble filters were too bright for my liking and made the earphones more harsh and sibilance-prone. The gold high midrange/medium treble filters perform as expected, raising the midrange and upper midrange. This setting is still brighter than the gray filters I preferred, though fans of a forward midrange may very much enjoy it. The last set of filters, the blue medium-mids/low-treble, were the least impressive to me, lacking a little in the way of clarity compared to the stock gray filters with no discernible gains elsewhere.

Keep in mind that the filters are only independent to an extent – making changes to one outlet can affect airflow through others. Therefore, swapping from one filter to another may have slightly different effects depending on the settings of the other ports.


After testing all of the filters, I used the neutral configuration of the FLC8 in most of my listening and A:B comparisons, except where it was an especially poor signature match.

In this configuration, the FLC8 has powerful bass that hits harder compared to most balanced-armature in-ear monitors, even relatively bass-heavy ones such as the EarSonics SM64. The SM64 has a noticeably less rich and impactful – though also marginally more controlled – low end. Same goes for relatively balanced-sounding dynamic-driver sets, such as the Philips Fidelio S2 and VSonic GR07 Bass Edition. The bass quantity reminds me of another hybrid earphone, the Fidue A83, and falls short of truly bass-heavy sets such as the Sennheiser IE 800 and JVC HA-FX700. Bass extension is very good and bass quality is superb for the quantity.

Equally impressive is the clarity of the FLC8 – the mids, while not at all forward in the stock configuration, can’t be called recessed either and are impressively close in clarity to high-end analytical earphones like the Brainwavz B2 and VSonic VC1000. The FLC8 is noticeably clearer than the very capable TDK BA200, EarSonics SM64, and Philips Fidelio S2. There is no upper midrange dip as there is, for instance, on the SM64 and Fidue A83, which allows the FLC unit better crispness and overall resolution, as well as superior vocal intelligibility.

Moving on up into the treble, the FLC8 strikes a fine balance of presence and smoothness. Even in the stock configuration it’s not a very forgiving earphone and can probably be classified as “slightly bright” on the whole. At higher volumes it gets harsher, as is usually the case with this type of sound sig, but still fares better than the excellent DUNU DN-2000, for instance. As expected, darker-sounding earphones like the TDK BA200 and EarSonics SM64 are smoother and more forgiving, but lack the sparkle and energy of the FLC8.  Its strong treble presence and excellent end-to-end extension also give the FLC8 some advantage in dynamics in soundstaging, beating the TDK BA200, SM64, and Fidelio S2 in width and, with the exception of the SM64, depth and dynamics, by a margin.

Interestingly, I also found the sensitivity higher than implied by the earphone’s specifications – despite the 93dB/mW stated figure, the FLC8 actually exhibited above-average efficiency in my testing.


Select Comparisons

Note: unless otherwise noted, the neutral configuration of the FLC8 was used for comparisons

VSonic GR07 Classic ($99)

VSonic’s mid-range heavyweight generally competes well with pricier earphones, but the FLC8 is out of its reach. The bass of the FLC8, even in its “neutral” configuration, is deeper and more powerful, but the GR07 still impresses with its bass quality, matching if not beating the FLC8 in control and the overall realism of its bass presentation.

The biggest advantage the FLC8 has over the GR07 is its midrange. There, the FLC8 is more natural, with a more crisp, resolving sound and vocals that are more upfront and realistic. The slight midrange recession of the GR07 causes the mids of the VSonic unit to sound less clear, less detailed, and significantly more laid-back, even distant, compared to the FLC8.

The FLC8 is a touch brighter overall. It can be more revealing, but still sounds more natural than the GR07, thanks in part to the more level midrange and to the GR07’s greater sibilance. Also worth noting is the higher efficiency of the FLC unit.

DUNU DN-2000 ($280)

The DN-2000 is perhaps the closest overall match for the FLC8 in my IEM collection. Like the FLC8, it is a triple-driver hybrid earphone with a sound signature slightly on the v-shaped side of neutral. Both earphones have similar strengths, including bass punch, clarity, and soundstaging. The differences between them are subtle, but add up.

The DUNU boasts a little more of both bass impact and depth, for instance. Modifying the configuration of the FLC8 from “neutral” by moving to the high sub-bass port helps in this regard, but the DN-2000 still maintains slightly better depth. On the whole, the FLC8 sounds a little warmer than the DN-2000, thanks largely to its less bright treble presentation. Its bass still provides plenty of impact when called for but on average is a little more subtle and less intrusive compared to the DUNU unit.

The FLC8 has an overall less v-shaped sound signature with a little more midrange presence. Combined with its marginally larger and more dynamic presentation, this makes for a slightly more natural sound. Up top, too, the DN-2000 is slightly brighter and more metallic-sounding, though both earphones tend to be rather revealing. In fact, depending on track I sometimes found the treble curve of the FLC8 to be more bothersome in terms of harshness and/or sibilance, and other times the DN-2000 was the bigger culprit.

InEar StageDiver SD-2 ($450)

The SD-2 is a warmer, more mid-centric sort of earphone than the FLC8, but it is one of the most capable such sets I’ve tried and makes for an interesting comparison with the “neutral” configuration of the FLC8. First, the FLC8 is a bassier earphone all around – depth, impact, rumble, and so on. The bass of the SD-2 is slightly tighter, but that is as expected due to the bass quantity difference. Taking the FLC8 into its low-bass configuration creates more parity between the two in bass quantity and quality, but makes the already-brighter FLC unit even brighter – a poorer signature match on the whole.

The FLC8 is clearer than the SD-2, due in part to its stronger treble, while the more level SD-2 appears mid-centric thanks to its lower bass quantity and duller highs. One advantage the SD-2 does have is smoother and more forgiving treble, which is something the FLC8 can’t match in any configuration. The presentation of the SD-2 is competent, but a mid-centric sound is never an asset when it comes to dynamics. On the whole, I found the FLC8 to sound more convincing more of the time thanks to a combination of better soundstaging and dynamics, clarity, and bass punch.

Westone W40 ($500)

The W40 is a quad-armature monster with a bit of bass enhancement and a warmer, darker sound signature. In its “neutral” configuration, I did indeed find the FLC8 to be more neutral than the W40 thanks to its brighter sound and broader frequency response. The bass of the FLC8 is not too different the W40 in overall power, but appears deeper thanks to a greater sub-bass focus and a less audible mid-bass hump.

The FLC8 is clearer through the midrange, but up top it sounds more harsh and sibilance-prone than the smoother, darker Westone unit. The FLC8 also has a wider and more “broad” presentation, as v-shaped earphones tend to do when compared to warmer or more midrange-focused ones.

I also switched the FLC8 to its bassier “pop/rap” configuration, but it didn’t make much of difference in this comparison. In this setting, the bass of the FLC8 was clearly more powerful than that of the W40 and the bass quality was more equal between the two. Despite this, the remainder of the comparison above still held true with the FLC8 remaining the brighter, clearer, and “wider” of the two earphones. Also, the FLC8 is more efficient than the quad-driver W40 in any configuration.

Audiofly AF180 ($550)

The signature of the AF180 is an interesting one, with some traits from smoother and more mid-focused sets such as the StageDiver SD-2 and TDK BA200, and others from brighter, more analytical earphones. Audiofly’s flagship IEM turned out to be a stronger competitor for the FLC8 than its counterparts from Westone and InEar, the W40 and SD-2/SD-3.

Once again, the FLC8 is the more efficient earphone. Its sound signature is more v-shaped, with deeper, more enhanced bass and brighter, more sparkly highs. This brighter tone is most noticeable with vocals. The FLC8 is a bit clearer as well, though also more prone to sibilance thanks to its extra treble energy. Where the AF180 shines is in providing a very flat and neutral midrange. Though vocals are a little more dull compared to the brighter FLC8, they end up sounding more prominent, full-bodied, and natural on the whole.

Value (9/10) – Despite the ever-increasing number of IEM offerings on the market in 2015, it’s rare to come across an earphone as unique as the FLC Technology FLC8. The main draw is the flexible 36-setting sound tuning system, though I found it best viewed as two or three “base” sound signatures that can each be altered slightly to one’s liking.

TheHeadphoneList Recommended Badge 2015Not all of the possible tunings are brilliant and swapping out the ports is an exercise in patience and finesse even with the included tweezers and spare parts, but it’s pretty easy to alter the sound once you get the hang of it. Those who get tired of listening to the same sound signature – or aren’t yet sure of exactly what sort of sound they want – are certain to find extra value here.

It’s not just the tuning system that makes the earphone special, however – even if limited to the default tuning, the FLC8 would be a superb-sounding set with one of the lightest and most comfortable form factors among hybrid IEMs, and that already makes it worthy of a strong recommendation.

Pros: top-tier audio performance; functional sound tuning system allows for more adjustment than other variable-tuning IEMs; very lightweight and comfortable for a 3-driver hybrid
Cons: small, easy-to-lose/damage parts mean this is an earphone solely for enthusiasts






Living in the fast-paced city of Los Angeles, ljokerl has been using portable audio gear to deal with lengthy commutes for the better part of a decade. He spends much of his time listening to music and occasionally writes portable audio reviews across several enthusiast sites, focusing mostly on in-ear earphones.


219 Responses

  1. Hi ok I can get these or 3003i. Please help with advice? I have dunu 2000j and ie800 but looking for ultimate universal 3D out of the head e peri eve with the best detail retrival.

  2. Hi ljokerl,

    I have my GR01 running for about 3 years now, and have been liking every second of it. I’m going for a replacement since the cables will break soon.

    How does FLC8 compare to the GR01? What I liked about the GR01 is the instrument separation and balanced sound. I liked the sound even more than GR07, as the highs are clearer.

    If I’m aiming for a similar sound signature, is FLC8 a good choice, or is there any other recommendations that you think is better? Thank you very much!

  3. Hey ljokerl,

    Been reading your reviews since you did one for the Phonak PFE. Probably snagging an FLC8S based on your recommendation!

    This was a great review! Thanks for taking the time to write so many of them!

  4. Thank you so much for taking the time answering my questions! Decision is definitely sealed. Just waiting for my x5iii to come in.

  5. Soundstage is good, definitely above average.

    Never heard of fake ones, this is not an easy earphone to manufacture and it doesn’t sell tens of thousands of units like a Beats or Sony or Sennheiser, so the effort to make a fake one wound’t be worth it.

    Modern smartphones are pretty good, so while you may not get 100% performance out of the FLC8, you’ll still be better off with that than with a lesser earphone. I’ve never felt my Moto X Pure was a waste with any of my universal IEMs. Nexus 6P should be on a similar performance level.

  6. I feel the same way about my HD600… I’d definitely get rid of my “higher-end” cans first. Never selling the Sennheiser.

    Very glad my reviews have been helpful on your journey and that you’re now enjoying the FLC8. Happy listening!

  7. Hi ljokerl,

    Thinking of purchasing these, and I think you persuaded me with the really great review. Also, the highly customizable sound signature is a fit for me since my music is so confused. Just have three questions though:

    1. How is the soundstage with these?
    2. Are there any chances that I could possibly be buying fake ones (will purchase from ebay)?
    3. Will use these on with my Nexus 6p (haven’t purchased a DAP yet, but thinking of), am I doing an overkill though partnering this with a phone?

    Hope you can take a bit of time to answer.

    Noob audiophile 🙂

  8. Yeah, you are to be blamed for that! (LOL).
    I’ve been reading your reviews for years now, and I’ve almost never bought any IEM related stuffs without reading your reviews first. Seriously, you’ve no idea how much I appreciate the work you’ve done here (of course my wallet wouldn’t say the same thing :D).

    In relation to the collection I have, you are right, it is a bit too much indeed. I plan to sell some of them once I found the IEM that is perfect for my taste. (I did the same with Open Aired Headphone, I stopped looking and sold most of them once I got to the HD650). Perhaps there are some better ones out there, but the HD650 is more than good enough for me, especially for the price I got them for.

    BTW, I just received the FLC8S yesterday, and I agree with most of points you said. But while I agree that this is indeed a bright IEM, I don’t think that the sibilance is much worse than the EX1000 (maybe just a tad more) (using Gold, Red, Gray Filter). Of course, my ears are severely untrained compared to yours… LOL

    Few months away from receiving my Velvet, and I hope I can stop looking after this… Seriously, I should stop…

  9. That’s quite a collection – most could only dream of having two universal IEMs that are pretty much end-game for their respective signatures!

  10. Hey,
    Thank you very much for your response. Still haven’t received mine yet, but I just hope that the high will not be terribly sibilant (the MDR-EX1000 is probably the most I can handle, treble wise).

    And also, I just purchased the Velvet after reading your review. Based on your description, the Velvet should be an “end-game” for my taste (I love HD650).


  11. Between T20 and FLC8 definitely FLC8. A83 is more competitive in detail, but I’d still give it to the FLC8. And comfort is no contest, FLC8 is a lot smaller and lighter than the other two.

  12. Hi Joker, nice review. I have an obsession with detail in a headphone. One time, I was listening to the Shure se846 and the detail in the mids was genuinely surprising; string instruments sounded like they were actually in front of me, like actual wood and vibrating springs. I’m replacing my fidue a83’s due to build quality and comfort issues. I’m trying to decide between the flc8s’ and the rha t20’s, and I was wondering which one you felt had the higher level of detail. Thanks!!!

    TLDR: which has more detail: fidue a83s, flc8s, or rha t20?

  13. I doubt you will see much of an improvement with the E7 over the 6S, but it’s best to just try it for yourself and go from there. I don’t find the FLC8 to have issues with “regular” (non-audiophile) sources, and iPhones are generally way better than average in that category.

  14. Hi ljokerl,

    So I just purchased the 8S (currently in the mail), and I’m wondering since I am using the iPhone 6S Plus mainly as the player, will I have any problem with the 8S? Because this one has an unusually low impedance (11ohm) while the iPhone has a relatively high output impedance (3-4ohm I’m guessing).

    I do own the FiiO E7, which nowadays I haven’t been using very much (because of the touch screen on the iPhone).

    I also have a 4R, which I quite like but wants a little more impact on the low ends.


  15. Hey again, thank you very much again for your input.

    I guess in the scenario you describe above, I imagine you would lean back to the FLC8s to be the best IEM in terms of bang for your buck, price to performance ratio in the context of being plugged into and iPhone SE almost exclusively. Is that right? I want to use these IEMs predominantly for on the go. Long bus rides and walking and stuff like that.

  16. Right, I probably wouldn’t buy a $1200 custom specifically for use with a phone much the same way I wouldn’t buy a 60″ 4K TV to watch basic cable or a high-end sports car to sit in traffic. That’s not to say you will have the same experience as with a less expensive earphone, it just comes down to the magnitude of the difference vs price paid. However, everyone’s finances and level of enthusiasm is different, and I’m sure there are some who would disagree about all three examples.

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