6 Knowles BA | DLP 3D printing |
80.6mm ultra-long sound tube |
4-way electronic crossover |
3 sound adjustment switches |
8-strand monocrystalline silver-plated copper cable |


6 Knowles Balanced Armature IEM


The 6 Knowles BA drivers per ear, together with the carefully-designed 4-way crossover and low-frequency ultra-long sound tube, completely covers the entire audible frequency range with a sound that will take your breath away.


Higher/ultra-high frequencies: handled by the SWFK-31736 driver that blends extreme resolution with rich sound
Mid-frequencies: EJ-33877 custom driver collaboratively created by FiiO and Knowles, with powerful mids that give lush vocals
Lower frequencies: HODVTEC-31618 driver, with 2 woofers that produce dynamic and authoritative bass


A whole new level of sound
6 Knowles BA driver custom setup

The FA9 marks the first time FiiO has employed Knowles EJ balanced armature drivers, commonly used among high-end IEMs. FiiO and Knowles collaborated to come up with the custom EJ-33877 driver for use in the FA9 for excellent mid-frequency performance with hauntingly realistic vocals.

More lifelike sound than ever
Custom Knowles EJ BA driver

Pleasing your eyes and ears
Scientifically-designed ergonomics

Thousands of individuals’ ear model data were used in designing the FA9, allowing us to create a smaller design that is comfortable for the vast majority of listeners.

In order to achieve the purest sound performance and to ensure the multiple drivers do not interfere with each other, the FA9 employs a specially-designed, ultra-long sound tube 80.6mm in length. The sound tube acts as a low-pass filter that effectively filters out unneeded extra mids and highs from the drivers to ensure a seamless frequency response. The sound tube also ensures the mid-bass is smooth and clean while enhances bass texture in general.

80.6mm ultra-long sound tube
Specially-designed acoustic filter

The FA9’s use of electronic crossover technology allows you to tune the sound to exactly the way you want with 3 sound adjustment switches. The impedance, bass, mids and treble adjustment depends on what music you are listening or what your preferences are!

Make it truly yours
3 sound adjustment switches
8 possible sounds

• S1 switch on: lower impedance and higher sensitivity, making the FA9 easier to be driven
• S1 switch off: higher impedance for a more clean and natural sound, with a darker background and lower audible noise from the source
• S2 switch on: treble boost, perfect for those seeking more highs and for rock music
• S2 switch off: treble normal for more balanced tuning, suitable for most types of music
• S3 switch on: reduced bass and increased mids, useful when listening to human voices and musical instruments 
• S3 switch off: increased bass and reduced mids, good when listening to classical and orchestral music

An all-new diamond-cut faceplate is integrated perfectly with the seamless translucent-black resin shell for a gorgeous look. And when you look at the FA9 from different angles, you can see a dazzling effect like those of numerous stars in the night sky.

Beautiful at any angle
Diamond-cut faceplate
Seamless translucent shell

Unlike most other 3D printed headphones, the FA9’s entire shell is created through DLP 3D printing technology. Now in its 4th generation, the printing accuracy, efficiency, and curing uniformity have been significantly improved from the past iterations of DLP 3D printing. This allows the FA9 to have an extremely precise and robust structure that is fully optimized for audio that is difficult to achieve with traditional manufacturing methods.  

The beauty of unprecedented precision
4th generation DLP 3D printing


The material of resin is especially important when designing a 3D printed earphone. Thus, we chose to use EU IIA certified, German high-transparency resin for its fine texture, skin-friendliness and comfort, as well as its resistance to discoloration.

EU IIA Medically Certified
High-transparency skin-friendly resin material

Thanks to the optimized 3D printing manufacturing and skin-friendly resin materials, the FA9 is lightweight at 6.2g per each ear unit and fits closely and comfortably to your ear, further allowing you to enjoy your music.

Born light and comfortable





The included 8-strand monocrystalline silver-plated copper cable gives you excellent sound quality out of the box, so you don’t have to worry about upgrading to a better cable.

8 strands of pure audio goodness

Details matter

• Expanded MMCX connectors
• Left blue and right red unit markers
• Gold-plated 3.5mm plug

• Imitation leather
• Self-closing cover 
• Mesh storage area
• Inner lining protection

Exquisite leather case for careful storage

标配SpinFit 360度可旋转硅胶耳套,使耳塞能够自由地旋转,轻松契合耳道,提升高低频音域。

沉沦其中的舒适感,标配SpinFit 耳套


Comprehensive accessories
Protected inside and out

HB3 leather case, 15 pairs of ear tips (balanced sound*3, enhanced bass*3, enhanced vocals*3, Spinfit*2, foam*2, double-flanged*1), SK-01 magnetic cable organizer, brush

Four-way crossover
Igniting a fire within your heart

The four-way crossover design has been applied so that each driver works perfectly in harmony with each other for seamlessly coherent low, middle, high, and ultra-high frequencies. With dynamic bass, crystal clear yet lush vocals, and extremely detailed yet pleasant treble, the FA9 will get you excited about your music again.

Always professional
Hi-Res Audio certifie