Speakers are one of those components that are simple to use, but difficult to simulate. Most of us have used a simple resistor to do the job. But a speaker’s response is much more complex, and while that might be enough for a simple simulation the fidelity is nowhere near close. [Sourav Gupta] recently shared his technique for modeling speakers and it looks as though it does a credible job.
[Sourav] shows how a simple resistor and an inductor can do the job, but for better fidelity you need more components to model some mechanical effects. The final model has six components which keeps it easy enough to construct but the problem lies in finding the values of those six components. [Sourav] shows how to use the Thiele-Small parameters to solve that problem. Speaker makers provide these as a guide to low frequency performance, and they capture things such as Q, mass, displacement, and other factors that affect the model.
If you can find those parameters — often known as TSP — then you can use the formulae provided to get the component values. There’s even a real-word example for a specific speaker. We would have been interested to see how the simulation stacked up to a real speaker, but this is still an interesting post.
Of course, if you grab a surplus speaker you may or may not be able to find the TSP data. At that point, you could make some guesses or measurements, but it certainly won’t be as easy.
The techniques in the post were not simulator-specific, so they ought to work with whatever tool you use. Our favorite browser simulator, Falsted, doesn’t have a speaker (but it does have an audio output port). The same tricks should work in LT Spice, too.