Loudspeaker analysis -- Thermal effects in a transient solution

For this loudspeaker analysis, we set up a transient analysis for a 4 kHz current waveform and looked at the induced eddy currents in the central pole and the top plate. Part of the process consisted of generating two separate magnetic analyses (Transient and Transient with Motion), and then using the power loss results to generate a thermal solution.

Heat source regions - Regions were added in the center pole and top plate to represent the heat sources for the thermal model. These regions are very finely meshed so that the eddy currents can be properly calculated. Before we could obtain the thermal solution, we had to solve the magnetic model. From the magnetic solution, the time-averaged power losses, for each of the heat source regions, were noted and then used as inputs in the thermal model.

Voice coil - Having the voice coil frequency set at 4 kHz minimized the motion and effectively kept the coil in a fixed position. In order to analyse the effects of motion, parameters were added to the voice coil, allowing it to move with the current input.

Results

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Transient without Motion (thermal model) Convection was used as the primary heat loss mechanism.

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Transient without Motion -- (Static thermal analysis) The resulting steady state temperature distribution for a 1 Amp, 6 Watt RMS input signal.

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Transient with Motion -- (Static thermal analysis) The steady state temperature distribution for a full transient with motion analysis.