The latest FD3 series of IEMs boasts a large 12mm dynamic driver unit with full-DLC diaphragm material. DLC(Diamond-Like Carbon) is a highly rigid material that also has an extremely lightweight structure that reduces unnecessary vibrations and makes the driver more responsive and clean sounding. It uses strong magnets that produce a strong magnetic flux of up to 1.5T. This helps in a deep-diving lower end and a highly detailed, ultra-low distortion in the high-end frequencies.
FiiO FD3 features an acoustic prism in the front cavity. It is fitted close to the front end of the cavity. This helps in precisely controlling the sound waves travel inside the cavity, reducing high-frequency response, and provides an overall sound wave diffusion. It also helps in reducing the distortion in the output and enables the pair to produce a clean output.
The semi-open design of the FD3/FD3 Pro on FiiO's patented technology for balanced air pressure within brings several advantages. Not only does such a design lead to more natural sound. but it also effectively protects your hearing by balancing air pressure within the FD3/FD3 Pro leading to less pressure on your eardrums. This makes your listening expenenceless tiring and the sound less forced.
While both the FD3 and FD3 Pro have the same cavity design and structure, the only difference between both pairs is the included cable. FD3 comes bundled with a 4-strand 120-core high-purity single-crystal copper cable with a fixed 3.5mm termination plug. FiiO FD3 Pro comes with a heavier, 8-strand 152-core Litz structure silver-plated monocrystalline copper cable with interchangeable termination plugs. It included 3.5mm SE, 2.5mm Bal, and 4.4mm Bal plugs in the package.