1. Introduction
This manual provides detailed instructions for the proper use and maintenance of your FiiO FD3 PRO In-Ear Earphones. Please read this manual thoroughly before using the product to ensure optimal performance and longevity.
2. Package Contents
Verify that all items listed below are present in your package:
- FiiO FD3 PRO In-Ear Earphones (Left and Right)
- High-purity monocrystalline silver-plated copper cable with interchangeable audio plugs (2.5mm, 3.5mm, 4.4mm)
- Various ear tips (balanced, bass, vocal)
- Carrying case
- MMCX removal tool
- Cleaning brush

Image 2.1: Contents of the FiiO FD3 PRO package, including earphones, cable, various ear tips, and a clear carrying case.
3. Product Features
- Flagship-level DLC Diamond Diaphragm: Equipped with a 12mm dynamic driver featuring a Diamond-Like Carbon (DLC) diaphragm. This design provides high rigidity and low weight, contributing to excellent transient response and minimal distortion for clear, powerful sound.

Image 3.1: Close-up diagram illustrating the internal structure of the FiiO FD3 PRO's 12mm dynamic driver with a DLC diaphragm.
- Flagship-grade Acoustic Prism: Incorporates an acoustic prism system designed to eliminate high-frequency standing waves, enhance sound wave diffusion, and address time delay issues within the earphone cavity, resulting in improved sound quality.

Image 3.2: Cross-section diagram highlighting the acoustic prism component within the FiiO FD3 PRO earphone.
- Semi-Open Design: Features a patented semi-open design that balances air pressure inside the earphones. This contributes to a more natural sound presentation and reduces pressure on the eardrums, enhancing listening comfort.

Image 3.3: Diagram illustrating the semi-open design of the FiiO FD3 PRO, showing air vents for pressure equalization.
- 2.5D Film Coating Glass Faceplate: The earphone shell features a unique celluloid panel covered with 2.5D film coating glass, providing a transparent aesthetic. The main body is constructed from aluminum-magnesium alloy, processed using five-axis CNC and hand polishing, ensuring durability and a lightweight feel.

Image 3.4: A close-up view of the FiiO FD3 PRO earphone showcasing its 2.5D film coating glass faceplate and aluminum-magnesium alloy body.
- High-Purity Silver-Plated Copper Cable: The FD3 PRO includes an exclusive cable made of high-purity monocrystalline silver-plated copper, featuring 8 strands of 19 wires each (total 152 wires) braided in Litz Type 2 style. It includes interchangeable audio plugs (2.5mm balanced, 3.5mm single-ended, 4.4mm balanced) for compatibility with various audio sources.

Image 3.5: The FiiO FD3 PRO's high-purity silver-plated copper cable with its interchangeable 2.5mm, 3.5mm, and 4.4mm audio plugs.
4. Setup Instructions
4.1 Attaching the Cable
- Identify the left (blue marking) and right (red marking) earphone units.
- Align the MMCX connector on the cable with the corresponding port on the earphone unit. Ensure the cable is oriented correctly (the pre-formed ear hook should curve over your ear).
- Gently push the connector until it clicks into place. Do not force it.
- To detach, use the provided MMCX removal tool or firmly pull the connector straight out while holding the earphone unit. Avoid twisting.
4.2 Selecting and Installing Ear Tips
Proper ear tip selection is crucial for sound quality and comfort. Experiment with the various types and sizes provided:
- Balanced Ear Tips: For a neutral sound signature.
- Bass Ear Tips: Designed to enhance low-frequency response.
- Vocal Ear Tips: May emphasize mid-range frequencies for clearer vocals.
To install: Gently push the ear tip onto the nozzle of the earphone until it is securely seated.
4.3 Changing Audio Plugs
The FD3 PRO cable features interchangeable audio plugs:
- Unscrew the currently attached audio plug from the cable.
- Select the desired plug (2.5mm balanced, 3.5mm single-ended, or 4.4mm balanced) and screw it onto the cable connector until secure.
- Ensure the connection is firm before connecting to your audio source.
5. Operating Instructions
5.1 Wearing the Earphones
- Insert the earphone units into your ears, ensuring a comfortable and secure fit. The cable should loop over the top of your ears.
- Adjust the cable and ear tips until a good seal is achieved. A proper seal is essential for optimal bass response and sound isolation.
5.2 Connecting to an Audio Source
Connect the appropriate audio plug (2.5mm, 3.5mm, or 4.4mm) to your audio player, amplifier, or DAC. Ensure the volume on your audio source is set to a low level before playing audio.
5.3 Volume Control
Adjust the volume using your connected audio source. Avoid listening at excessively high volumes for prolonged periods to prevent hearing damage.
6. Maintenance and Care
- Cleaning: Regularly clean the ear tips and earphone nozzles with the provided cleaning brush or a soft, dry cloth. Ensure no earwax or debris accumulates in the nozzle.
- Storage: When not in use, store the earphones in the provided carrying case to protect them from dust, moisture, and physical damage.
- Cable Care: Avoid sharp bends or excessive pulling on the cable. Detach the cable by pulling on the connector, not the wire itself.
- Moisture: Keep the earphones away from water and high humidity. They are not water-resistant.
7. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| No sound or intermittent sound |
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| Poor sound quality (lack of bass, muffled sound) |
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| Static or crackling noise |
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8. Specifications
| Feature | Detail |
|---|---|
| Model Name | FD3 Pro |
| Ear Placement | In Ear |
| Connectivity Technology | Wired |
| Headphones Jack | 3.5 mm Jack (interchangeable with 2.5mm and 4.4mm) |
| Audio Driver Type | Dynamic Driver |
| Audio Driver Size | 12 Millimeters |
| Diaphragm Material | Diamond-Like Carbon (DLC) |
| Impedance | 32 Ohm |
| Frequency Range | 20 Hz - 20,000 Hz |
| Cable Feature | Detachable MMCX, High-purity monocrystalline silver-plated copper |
| Interchangeable Plugs | 2.5mm, 3.5mm, 4.4mm |
| Material | Aluminum-magnesium alloy body, 2.5D film coating glass faceplate |
| Item Weight | 7 Grams (per earphone) |
| Water Resistance Level | Not Water Resistant |
| Manufacturer | FIIO |
| Product Dimensions (Packaging) | 9.45 x 27.17 x 0.98 inches |
9. Warranty and Support
FiiO products typically come with a limited manufacturer's warranty. Please refer to the warranty card included in your product packaging or visit the official FiiO website for detailed warranty terms and conditions specific to your region.
For technical support, service, or inquiries, please contact FiiO customer service through their official website or authorized distributors.
Official FiiO Website: www.fiio.com





