The air spring effect of flat panel speakers
Der Luftfeder-Effekt von Flachlautsprechern
Flat panel speakers are characterized by its low manufactured depth. Compared with conventional loudspeakers the space saving integration in existing surroundings is an advantage. From the acoustics point of view disadvantages come along with the low manufactured depth that influence the reproduction in the lower and middle frequency range. Based on measurements and FEM-simulations the reasons for this behavior were analyzed. Supplementary methods for solving this problem have been considered that are derived from conventional loudspeaker technologies. It has been shown that the advantage of flat panel speakers mounted next to a wall or other sound hard boundaries caused sound radiation problems. In case of flat panel speakers, mounting in a baffle or an enclosure can be a solution. But due to acoustic short-circuit and stiffness of the air volume inside an enclosure unwieldy large baffle or cabinet dimensions are necessary. Furthermore simulation and measurement results show that the stiffness of the air spring seems to be independent on the enclosure shape. The air spring of flat enclosures are comparable to the air spring of non-flat enclosures with the same volume. But the flat enclosures have to be very broad to offer the same air volume like an conventional enclosure. Otherwise, the resonance frequency and thus the lower cutoff frequency will be increased. Therefore approaches to handle or reduce the air stiffness of small enclosures have to be further investigated.