Headfonics 2018

FiiO F9 Pro Review

The FiiO F9 Pro is a revision of the existing F9 IEM and will sell at a slightly higher price of $139.99. It will continue to be sold alongside the F9.

Disclaimer: The FiiO F9 Pro sent to us is a sample in exchange for our honest opinion. We thank FiiO for this opportunity. 

To learn more about FiiO reviews on Headfonics you can click here.

Note, this review follows our new scoring guidelines for 2020 which you can read up on here.

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I was lucky to have the privilege of being invited by FiiO for the launch of the F9 Pro back in Nov 2017 at the Dong Fang Hotel in Guangzhou, China. I even made a presentation there though how much any understood is up for debate. My Chinese is not that good.

I did, however, get a sense of some nuanced pitches that day that may get lost in translation when it comes to reading the FiiO website. The F9 Pro is not just a tweaked version of the original F9 but also an improved outcome of the growing relationship of FiiO and Knowles who contributed to the driver technology found inside the F9 Pro.

The F9 marketing collateral made no mention of the Knowles partnership at the time so the F9 Pro should be seen as bringing in a new era of sorts on FiiO IEM armature assemblies. Priced at $139.99 it is their most expensive IEM to date, $40 higher than the original F9. In relative terms, however, this is still what I would classify as a potential ‘bang for buck’ offering.

What Is The Pitch?


The pitch is fairly similar to the F9 with one or two important tweaks. At its core, this is a keenly priced hybrid IEM using a single dynamic 9.2mm driver for the lows and a dual-BA driver design for the mids and highs.

It comes as part of the continuing Infinity Sound theme FiiO has been using since the summer of 2017. That means, like the F5 and F9 before it, the F9 Pro comes with both balanced and unbalanced capability (2 cables) and is referenced against their similarly designed balanced capable DAPs and DAC’s including the Q5, Q1 Mark II, X3iii, X5iii, and the X7ii.

F9 Pro Launch Event

Internal tweaks

The F9 Pro pretty much retains all of the positive features of the F9 such as the strong shell construction, excellent packaging, and dual cable approach but it does tweak here and there. Partly due to feedback and also internal design possibilities. In comes Knowles TWFK-30017-000 balance armature drivers which in turn has helped FiiO to fine tune the sound of the F9 Pro. FiiO have retained the PEK designed 9.2mm dynamic driver for the low-end response.

Physical Tweaks

Also included are some build changes for enhanced usability such as better MMCX connector positioning for a wider range of aftermarket MMCX cables compatibility, color-coordinated MMCX rings for easier left/right visibility and double the number of tips available.

FiiO F9 Pro


Form Factor

The form factor and design are the same as the F9 with only some minor but very useful changes. FiiO has opted to retain the CNC aluminum body of the F9 using a unique ripple effect. As before the engineering and finish of the F9 Pro body is excellent. The contouring is smooth and you will find no sharp edges on the surface.

FiiO also contends that the ripple design adds an additional level of durability to the F9 PRO shell as well as maximize the internal space of the body. As such it is not a huge IEM despite the long 9.2mm driver and roughly on par with RHA T series and certainly a lot smaller than the hybrid triple driver IT03 from iBasso.

Color Scheme

The changes are primarily in the color scheme and the positioning of the MMCX connectors on the top of the shell. The color scheme of the body is now a lighter gray tone as opposed to the darker black hue of the F9 (no comment on the red F9 as we never received one). I think it works a little better than the original black color by visibly accentuating the ripple contours a little more.

MMCX Repositioning

The second major tweak is the MMCX connector stem which is now thicker and slightly longer. This provides for a wider surface area at the end of the MMCX housing which in turns provides for more space to easily connect the supplied cables. And it works. I often found the narrow base of the F9 to just be a little hard to work with for connecting. Now it is much easier as well as providing more workable space for aftermarket MMCX cables and bulkier connectors to fit.

Cosmetic Changes

The final tweaks are more cosmetic but still useful. FiiO has added red and blue color rings to the base of the MMCX cable-side connectors to denote right and left and make it easier to quickly match up to your ear without checking for the physical label. The final change is the insertion of the word Pro on the inside of the shell using a white decal.

FiiO F9 Pro



The F9 Pro comes with two detachable cables with gold-plated MMCX connectors. The first is the unbalanced or stock black TPE coated cable 1.2m in length but this time it is terminated with a right-angle 3.5mm gold plated stereo jack. On the F9 it is a straight jack. The y-split barrel is also printed with the F9 Pro label. The F9 Pro unbalanced cable is also finished with red and blue rings on the MMCX side to denote left and right and provide enhanced visibility for easy matching.

The cable wire is still a 24-strand braided OFC cable with TPE used to protect from unnatural coloring from oxidization, corrosion, and aging. This is pretty much the default cable for those using an unbalanced DAP or 99.9% of all smartphones.

Remote & Mic

Note, because of the lack of MFi for the F9 Pro the unbalanced cable does not have a specific iOS to Android switching function but it does have an inline remote and mic module.

The performance of the remote is patchy. For iOS, it will play and pause but no volume control on iOS10 on an iPod Touch. For Android Nougat 7 on an LG G6, I did get full volume control and play and pause on the stock music player. However, I only had volume control using the HiBy Music app. Mic functionality was fine and I had no issues with in-call use during the testing.

FiiO F9 Pro


The second cable is a 2.5mm balanced 1.2m MMCX terminated cable which is also made with a TPE jacket. It houses a superior SPC wire to the OFC of the F5. This is a 1.2m braided black PET jacketed 4-core cable which splits into 2 beyond the y-split. It is terminated with a 2.5mm TRRS gold plated plug. Like the unbalanced cable, it also comes with a right-angle jack as opposed to the F9 straight jack. The y-split barrel is also printed with the F9 Pro label

The F9 Pro balanced cable is much softer than the F5 balanced cable with better pliancy and lower microphonics. The good news is if you have an F5 you can simply swap them over as both are MMCX terminated.  The F9 Pro balanced cable is also finished with red and blue rings on the MMCX side to denote left and right and provide enhanced visibility for easy matching.


Both cables are finished with the same F9 long memory retentive hooks. It retains its overall shape though as opposed to user-customized shaping. It will bend and flex to your needs but once off your ear, it will snap back to its original curve.


One final note, the MMCX connection is strong with a healthy snap when put in place. It is also now much easier to attach and detach than the F9 due to the wide stem length and base. It still requires just a gentle wiggle will ease them off. I found a slight twist and bias pressure outwards in one motion snapped the cables off very easily. If you pull back with force you won’t be able to get them out and worse you could damage them.

Comfort & Seal

Comfort and fit are a very similar experience to the F9 though the additional foam tips will provide a slightly better experience. The F9 did not come with foam tips. The large venting on the inside shell will take a little away from the isolation of an otherwise excellent fit.

The over the ear cable experience was excellent with very little microphonics creeping up with either cable into my ear. Comfort wise, I can have no complaints. The rounded curves of the F9 Pro made this a very smooth insert and it stays fairly secure in my ear. That additional depth I would have liked on the F9 has been satisfied with the inclusion of those foam tips also which insert a little deeper for me.

FiiO F9 Pro


The supplied tips with the F9 Pro are much better with a wider range of choice which now includes foams. The total count is now doubled from 6 sets of tips to 12. The wide and narrow single bore tips have been retained from the F9.

The additional six sets are 3 sets of clean white and red stem single bore silicone tips and 3 sets of foam tips. The clean white attenuates the top end a little more than the original tips with a bit more focus on upper mids and lower treble. The foam tips will relax the top end even further and accentuate the low-end but they will seal the best.

Accessories & Packaging

The external packaging on the F9 Pro is virtually the same as the F9. This is an all-black open-top cardboard box though instead of pics of the red and black shell variations fo rthe F9 on the front you just get the gray shell of the F9 Pro. Perhaps the most prominent change is the additional Knowles marketing line in white at the bottom of the box celebrating the new relationship with FiiO.

The F9 Pro internal packaging has the drivers on display outside the hard case whereas before they were found on the inside of the box. The F9 Pro uses the same etched hard case as the F9 though on the inside there is no use of cardboard tip carriers and they are instead inside simple plastic white bags. That makes sense. I was never a fan of the cardboard holders as they fall apart easily and 12 sets are kind of hard to pack in without going to lightweight bags.

The full breakdown os what is inside is as follows:

  • Carrying case
  • Ear tips x 12 pairs
  • Warranty card
  • 3.5mm single-ended cable with in-line controls
  • 2.5mm balanced cable
  • Water-resistant neoprene carrying pouch
  • Quick start guide

FiiO F9 Pro

The additional soft zip pouch is a nice touch. It adds some enhanced pocketability to the F9 Pro that the hard case cannot offer. Simply switch to the hard case if you are sticking your F9 Pro in a bag and then alternate to the soft pouch for your smaller on-person or bag pockets and you are good to go.

Click On Page 2 Below for Sound Impressions & Comparisons

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