Simple sealed box simulation
The aim of this exercise is to familiar the design flow of AKABAK. A simple sealed box with a cone loudspeaker driver is used. In contrast to the previous pressure box (direct-sound analysis) example, we move into the “heart” of the software – BEM. There are more steps needed to accomplish it.
The enclosure and driver dimension are somewhat arbitrary. Outer dimension of the enclosure is 100 x 170 x 110 mm. Uniform wall thickness of 5 mm is assumed. Symmetry along z-axis is used. Hence, BMR parameter dialog is as shown below.
We therefore only need to define nodes of one-half size of the box and driver. Note we need to define both nodes for external and internal walls as depicted below.
Nodes for setting observation fields and points are needed as well. Two subdomains are used. Subdomain with EIType = exterior is used for the free space (enclosure external). Subdomain with EIType = interior is used for enclosure internal.
Neumann boundary type is set for enclosure external elements. On the other hand, wall impedance is selected for enclosure internal elements.
Shell component is used to model the driver front surface which is belong to the enclosure-external subdomain. The rear driver surface associated with the enclosure-internal subdomain is inherited from the front surface.
Lumped-element schematic is illustrated in the next figure. The parameters are somewhat “typical” for a 4” driver.
BEM and field mesh size are rather large to minimize computational time. Once the model has been solved with error, we can increase mesh density.
Enclosure internal ad external nodes.
Node for observations.
BEM exterior subdomain.
BEM interior subdomain.
Observation setting.
Result.
The file for download
http://akabak.pansonaudio.com/Sealed LE+BEM Box 1.akp
Let me know if you find any error. Have fun!