Lumped Speaker Boundary
The Lumped Speaker Boundary condition is used to model a loudspeaker (dust cap, cone, surround assembly, and motor) or another transducer using a lumped representation with a coupling to an Electrical Circuit interface. The mechanical and electric properties of the speaker can, for example, be described through a Thiele-Small parameter representation and associated lumped parameters.
In the time domain, nonlinear effects can be included in the lumped model through parameters that depend on the axial position x or velocity v of the speaker. These are, for example, the typically measured BL(x), CMS(x), or RMS(v). Predefined variables exist for the axial velocity tatd.lsb1.v_ax and an ODE is solved for the associated axial position tatd.lsb1.x_ax (use the appropriate physics and feature tag). These variables can be directly used in expressions in the electric components in the Electrical Circuit model as they are globally defined.
The properties of a back volume can also be modeled using a lumped representation through either a simple equivalent acoustic compliance or a more general RCL circuit representation. On the other hand, if the air domains on both sides of the speaker are modeled explicitly (included in the model) then there are two possible setups:
1
If the speaker diaphragm is represented by an interior boundary (a “shell” with air domains on both sides): use the Interior Lumped Speaker Boundary condition.
2
If the speaker diaphragm is represented by a domain (a “solid” with air domains on both sides): use two Lumped Speaker Boundary features, one applied to the upper side and one to the lower side. Make sure the speaker axis is the same on both sides and that the back volume correction is disabled (the No correction option). Finally, in the Electrical Circuit add two External I vs. U nodes in series, when setting up the coupling.
For the Speaker Geometry, Circuit, Mechanical, Thermal, Constraint Settings, Exclude Edges, and Exclude Points sections, see Lumped Speaker Boundary in The Thermoviscous Acoustics, Frequency Domain Interface.
For the Back Volume Correction and the Initial Value sections, see Lumped Speaker Boundary in The Pressure Acoustics, Transient Interface.
When the Lumped Speaker Boundary is placed next to a Wall or Interior Wall, with No slip as the Mechanical condition, it is necessary to exclude common points (in 2D axisymmetry) or common edges (in 3D). This is done in the Excluded Points/Edges section. To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.