Review: FiiO F9 Pro – Optimus Prime

FiiO F9 Pro

This is the area where things get much better. With the help of the new Knowles driver, mids sound blatantly better in every aspect. The F9 had a V-Shaped signature, but that is not the case with the Pro. By courtesy of a more effortless treble response and better tonality from the mid driver, mids now find the required space and freedom to shine. The tonality is especially much better and that is very easy to hear even during the first listening session.

Even so, the control is the biggest improvement in my opinion. The mids of the F9 contained a harsh peak on upper mids & lower treble, while this Pro version does not have such an issue. Even that alone gives you a much more coherent and a pleasing sound and it’s much easier on ears.

This is like jumping on a higher level IEM from a good one. Clarity, control, tonality, resolution, transparency… Everything you can think of, is improved with the F9 Pro. It preserves the good points and adds even more with its higher quality BA driver.


The F9 was peaky and aggressive with its lower treble response, but F9 Pro again irons that out with its much more controlled highs. This is a huge factor not just for the highs are concerned, but also for the whole sound reproduction. The smooth transition between the frequencies is very important in every IEM, and the F9 Pro is much more consistent in that sense.

FiiO F9 Pro

FiiO F9 Pro

Treble energy is just a little trimmed down for the sake of this consistency. But it still has very clear highs and the extension is similar. The improved treble quality effects many things, such as micro details, accuracy, texture and separation for the whole sound experience.

The positioning of the cymbals are very nice and distant enough to create a nice staging & image, together with the resolving character and good control. There is a slight roll off but nothing disappointing for the price level. I think the F9 did not have a noticeable problem with its upper treble, so the character on this part is quite the same, but the improved lower treble contributes critically to the F9 Pro to generate a consistent sound overall.


The clarity on the F9 Pro is simply very good for the money, and the new BA drivers serve absolutely great for the new -much improved- coherency. Also the mids are where they should be this time around, so the sound feels more linear and realistic. Resolution is quite the same and the F9 was already very good in that regard, especially for the budget level. But the F9 Pro contains closer vocals and instruments and that contributes very well for a resolving, balanced and smoother character.

Sound stage again is impressive for the money, although there’s no big difference from the F9. It’s not often to hear this wide staging and sharp imaging for this price. Channel balance is also quite good and separation is improved with the more consistent nature of the new BA drivers. Background blackness leaves good impressions once again with a nice, close to 3D feeling.

FiiO F9 Pro

FiiO F9 Pro

On the contrary, it’s still not the most controlled IEM around. When you crank up the volume to louder levels, you can hear that the control is not on a high level, and there’s a chance for elements of a fast song getting mixed up sometimes. Of course it’s much better and smoother than the F9, but don’t expect a TOTL speed, layering, separation and control from this IEM. The good thing is that, speed and dynamism are better than the F9 and that sometimes makes a big difference with certain genres/songs.

The FiiO F9 Pro has a sensitivity of 106dB and an impedance of 28 ohms. The values are the same with the F9, so it’s quite easy to drive.


This review already contains the comparison with the F9 in the context, so I’ll go on with other IEMs for comparison.

Shozy & AAW Hibiki: Hibiki is a single dynamic driver IEM, and gives an airy bass like the F9 Pro. But the latter has more punch and rumble most of the time, and has more midbass presence as well. Mids are very good with the F9 Pro, and as you know if you’ve read the Hibiki Review, its mids are on the thinner side and tonality is not great. So overall F9 Pro is the better performer. Even so, the Hibiki is a great value for the money.

LZ-A4: The LZ is outstanding in terms of bass and with its open back design it’s really atmospheric and has great stage depth. Mids and trebles are quite good as well, but that depends on the filters being used. The FiiO F9 has much better fit and isolation, similar amount of mid and treble succession and build quality is better to me, except that doubt on the MMCX connectors. This is pretty close to be honest, and I think the winner will depend on the person’s taste and usage habits.

Also FiiO’s own F1 and F3 IEMs are no match for the F9 Pro in any aspect, although the F3 is a damn good sounding IEM for the money.

HiBy R6

FiiO F9 Pro


Let me quote my own review about the F9 here:

“For 100$, you get a very solid IEM with a great fit and ergonomic design and also a great sound quality. The only big problem here is the lower treble, which I think FiiO could make better with more precise tuning. There will be a FiiO F9 Pro model soon, and James from FiiO says it has better control overall, so it looks like you don’t need to worry about the peak after getting that version.”

Well, this time for 139$, you get everything the F9 offers, plus a much smoother and controlled sound with better dynamics, precision and tonality, which is crucial in my book. Slight upgrades in terms of usage is the icing on the cake. What more can we ask?

I recommend everyone to skip the F9 and get the F9 Pro. It’s really interesting to see how much the brand of the drivers makes this kind of an impact on sound. What if you have the F9 already? No difference, I would still recommend the Pro version to you. I think FiiO could’ve released the Pro model directly as the F9 model, but I’m not making the decisions of course.

This is the best IEM FiiO have ever released so far, and I hope they continue to offer great value in this market.

4.2/5 - (88 votes)

A keen audiophile and hobby photographer, Berkhan is after absolute perfection. Whether it is a full-frame camera or a custom in-ear, his standpoint persists. He tries to keep his photography enthusiasm at the same level as audio. Sometimes photography wins, sometimes his love for music takes over and he puts that camera aside. Simplistic expressions of sound in his reviews are the way to go for him. He enjoys a fine single malt along with his favourite Jazz recordings.


  • Reply February 13, 2018


    Thanks Berkham for your review. How do they sing with HiBy? Good matching? I have F9 Pro with Fiio X5 III and I am not particularly impressed. Would you swap the player?

  • Reply February 14, 2018


    Thank you too.

    Yes, I would swap the player. F9 Pro and Hiby pair very nice from the BAL output.

  • Reply February 14, 2018


    Good! Will consider highly your recommendation:)

  • Reply March 24, 2018


    I’m testing Shure SE 215 and FiiO F9 Pro. I can tell that bass is much better and deeper in Shure.
    Treble is different in both, Shure is well balanced. In FiiO treble is too intensive, not very natural however it’s a good quality.

  • Reply April 5, 2018


    Could you tell me if I have a good experience using this F9 Pro with a smartphone xiaomi (with internal dedicated dac) or they must be used with a specific DAP to reach a good result? At the same is different in terms of quality if i buy the F9 normal instead the Pro?

    • Reply April 6, 2018


      You should get the Pro model as it sounds much better. As for the smartphone, all devices have a dedicated DAC but that doesn’t mean anything. A phone will never sound on a level a good DAP does.

  • Reply April 8, 2018


    Sorry i am new to headphones and i want to get a pair of iems.I have about a budget of 250 usd.How should i spent the money worth?(sry for the bad english)

    • Reply April 9, 2018


      How will you use it? What musical genres? What source?

  • Reply August 31, 2018

    dhannjay sah

    very nice this blog

  • Reply August 31, 2018


    Thanks for the appreciation!

  • Reply September 12, 2018

    Sheridan Kamal

    May i know what type of cable that Fiio used for the balanced jack, is it necessary to change the cable to further improve the sound? Thanks.

    • Reply September 14, 2018


      “The 2.5mm balanced cable is made of silver-plated copper wire, which ensures a balanced sound signature and a high level of detail retrieval. Of course, due to its balanced nature, the left and right channel wires are separated so that there is significantly greater channel separation – leading to a richer, more detailed musical experience.”

  • Reply October 5, 2018


    Which is better between F9 PRO or Brainwavz B400?

    • Reply October 9, 2018


      I’ve never heard the B400.

  • Reply January 4, 2019


    How would you rate these against the Simgot EN700 Pro? Thanks.

    • Reply January 9, 2019


      I’ve never heard the EN700.

  • Reply February 25, 2019

    Rob Schschtet

    Comparing the 1 More Quad and the Fiio Pro 9, which one would you assess is better for classical music listening and why? And are there others in this price range even more suitable for classical
    Music? Thanks!

  • Reply June 25, 2019


    Does F9 Pro match with Shanling M0?

  • Reply August 10, 2019


    Hi Berkhan! Quite a detailed blog, many thanks for that.

    I have been inching towards ‘purer’ music while not splurging. I am looking to upgrade from Symphonized NRG 3.0 (~ $25, not so famous apparently, but bang for buck). I’ve been eyeing F9 Pro. I will be pairing it with Fiio MK3 (again, the starting baseline for Hi-Res DAC).

    Though it might appear counter-intuitive for this article, but would there also be other good earphones in this range that I could run my eyes over. I am looking to spend 5x vs. my old earphones, and plan to the make the best out of it 🙂

    Thanks in advance for the response.

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