In a ported speaker, the resulting bass frequencies are made by the bass woofer and the porting tube. The job of the porting tube is to further enhance bass extension and enhance bass control, for fast bass transients and overall better bass quality.
The FiiO SP3 features a 3.5-inch midwoofer that is larger than what is typically found in its class. What this means is that when playing music with a bass emphasis, the woofer vibrates more and thus more air is flowing through the speaker porting tube. Engineers have to take into account this flow of air when designing the porting system to ensure that the air flows smoothly so that the resulting bass is of high quality.
After going through dozens of different designs, FiiO engineers finally developed the innovative “double-diffused S-shaped porting tube”, which specifically allows the SP3 to meet its goals of being compact yet capable of producing high quality sound. First, this porting tube design features a much smaller cross-section than typical porting tubes, allowing the SP3 to remain small in volume. Second, FiiO engineers carefully created the “S” shape of the porting tube to maximize smooth air flow and minimize turbulence. Finally, damping is specifically placed at the inlet and outlet of the tube, for reduced audible noise and for a pure, robust bass quality. All in all, the SP3 will easily immerse you in a movie thanks to its ability to accurately reproduce sound effects.