The low-frequency performance of exciter-driven flat-panel loudspeakers is technically challenging. The lower modal density results in high deviations in the frequency response, and dips of more than 20 dB are possible. This paper presents an alternative approach for optimizing the modal behavior through the additional air spring effect of an irregular shaped enclosure. The additional mode-dependent air compliance suppresses the panel’s anti-phase components, which minimizes dips in the frequency response and improves the response without adding mass to the system. The approach is analyzed with the measured and simulated results of a prototype. Furthermore, additional enclosure changes were made to visualize the influence of the air spring improved system.