Compared with the first generation, the concept sound of the second generation has made a qualitative leap and is mature and stable. After all, it feels like middle-aged and fat. The main consideration is that a suitable cavity is helpful to improve the sound quality. This generation looks really much more obese and closer to mass production. Of course, the selection of materials and punching of the metal ring in the middle ring still cannot be solved. The aperture is small, the density is large, and the seamless design is required. Only large factories dare to try the cost estimate. Apple had a similar camera that year, which also used aluminum-magnesium alloy full-circle punching and seamless design to form a closed-loop sleeve. Looking at the current audio market, if there are similar products, Bose's small audio can do it, when its aperture is not small. So this thing can only exist concepts after all.