Optimizing the manufacturing parameters of carbon nanotubes stiffened speaker diaphragm using Taguchi method

This study developed a thermal transfer printing (TTP) technique to fabricate a carbon nanotubes (CNTs) stiffened speaker diaphragm. The self-developed TTP stiffening technique does not require a high curing temperature that decreases the mechanical property of CNTs. Therefore, the inherent strength of CNTs was preserved. In addition to increasing the stiffness of diaphragm substrate, this technique alleviates the middle and high frequency attenuation associated with the sound pressure curve of a speaker, thereby smoothing the sound pressure curve and achieving a full sound range as well as reducing bass distortion and enhancing treble clarity. Furthermore, the TTP technique can stiffen a localized area on a diaphragm substrate, thus increasing diaphragm stiffness without markedly raising diaphragm weight. The Taguchi quality engineering method was applied to identify the optimal process parameters (i.e., transfer area, stiffening pattern, coating layers, and transfer temperature). Finally, the optimal process parameters were employed to fabricate a stiffened diaphragm, which was then assembled onto a speaker. The result indicated that the stiffened diaphragm improved the smoothness of the sound pressure curve for the speaker, which produced a mid-frequency dip difference (ΔdB) of 1.9 dB and an attenuation peak frequency (f_peak) of 4220 Hz.