A theatre company envisioned an innovative, interactive play concept incorporating small speakers mounted on the shoulders of audience members. However, the original design posed a challenge as viewers inadvertently disrupted the experience by pressing buttons, altering the sound channels. To address this, the company sought our expertise in developing bespoke cases for these speakers. Overcoming the hurdle of the speakers’ round shape, we iterated through three design phases, continually testing and refining until arriving at a final approved prototype. Subsequently, we executed a serial production of approximately 100 units to realize their vision effectively.