An enclosure for an electronic device is enclosed. The enclosure includes rib structures configured to improve structural support to prevent damage and to dissipate vibration throughout the enclosure. The rib structure can receive a speaker module and a cap member. The rib structure and the speaker module can combine to form a three-dimensional volume allowing the speaker module in which the speaker module may project sound, thereby enhancing acoustic performance. Also, the cap member may be adhesively attached to the rib structure to provide additional structural support against vibration and abuse caused by load forces associated with a drop event.