Abstract
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.
Highlights
Flat-panel loudspeakers are becoming increasingly important for today’s consumer market [1].The invisible integration, wide and diffused radiation and improved room interaction are features of flat-panel loudspeakers, mentioned by Bank [2], for improving the perceived audio quality.large and more powerful devices can be integrated without disturbing customers’ views or disrupting the aesthetics of a room
The finite element acoustical (FEA) part is modeled with TET10 elements (a 10-node second-order isoparametric tetrahedral element with four nodes associated with the vertices and six with the edges) with 1 mm element size, causing a minor error of less than 1%
The compensation function Hc was calculated by comparing a reference measurement with the Klippel near field scanner (NFS) and the in-situ tests at a certain location in the anechoic chamber
Summary
Flat-panel loudspeakers are becoming increasingly important for today’s consumer market [1]. An alternative solution was presented by Anderson [14], who recommended the usage of an array of force drivers to selectively excite the lowest eigenmodes of the flexible panel This construction enables the same acoustic performance as a conventional speaker within the array-addressable frequency region. Compared to a simple cuboid enclosure, the irregular shaped enclosure can create local pressure changes that can cause a local panel stiffening This minimizes dips and improves the frequency response without adding mass to the system. A variation routine is performed, which further optimizes the frequency response by changing the shape of the enclosure
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